Here you will learn OSI Model Layer Introduction, overview of the 7 OSI reference model, applicaion, session, transport, network and physical layers. If you want to remember the sequence of the OSI layers model name then the following two sentences can help you a lot for this purpose.“All People Seems To Need Data Processing”. Open Systems Interconnection (OSI) model is developed by ISO (International organization for standardization) in 1984. OSI reference model is a logical framework for standards for the network communication.
OSI reference model is now considered as a primary standard for internetworking and inter computing. Today many network communication protocols are based on the standards of OSI model. In the OSI model the network/data communication is defined into seven layers.
These 7 layers further divide the tasks of moving the data across the network into subtask and hence complete one communication cycle between two computers or two network devices. Each layer is assigned a task and the task is completed independently. The OSI layers have the clear and independent characteristics and tasks.
The 7 layers of the OSI models can be divided into upper and lower layers. I have defined the characteristics, tasks and features of each layer separately.
Layer 7: Application Layer
The application layer defines the interfaces for communication and data transfer.
This layer also provides and support services such as job transfer, handles network access, e-mail, supports user applications and error recovery.
Protocols: FTP, DNS, SNMP, SMTP, FINGER, TELNET, TFTP, BOOTP and SMB protocol are operated on the application layer.
Network Devices: Gateway network device is operated on the application layer.
Layer 6:Presentation Layer
The presentation layer presents the data into a uniform format and masks the difference of data format between two dissimilar systems. It also translates the data from application to the network format. Presentation layer is also responsible for the protocol conversion, encryption, decryption and data compression. Presentation layer is a best layer for cryptography.
Network Devices: Gateway Redirector is operates on the presentation layer.
Layer 5: Session Layer
Session layer establish and manages the session between the two users at different ends in a network. Session layer also manages who can transfer the data in a certain amount of time and for how long. The examples of session layers and the interactive logins and file transfer sessions. Session layer reconnect the session if it disconnects. It also reports and logs and upper layer errors.
Protocols: The protocols that work on the session layer are NetBIOS, Mail Slots, Names Pipes, RPC
Network Devices: Gateway
Layer 4: Transport Layer
Transport layer manages end to end message delivery in a network and also provides the error checking and hence guarantees that no duplication or errors are occurring in the data transfers across the network. Transport layer also provides the acknowledgement of the successful data transmission and retransmits the data if no error free data was transferred.
It also provides and error handling and connectionless oriented data deliver in the network.
Protocols: These protocols work on the transport layer TCP, SPX, NETBIOS, ATP and NWLINK.
Network Devices: The Brouter, Gateway and Cable tester work on the transport layer.
Layer 3: Network Layer
The network layer determines that how data transmits between the network devices. It also translates the logical address into the physical address e.g computer name into MAC address. It is also responsible for defining the route, managing the network problems and addressing. Router works on the network layer and if a sending device does not break the data into the similar packets as the receiving device then network layer split the data into the smaller units and at the receiving end the network layer reassemble the data.
Network layer routes the packets according to the unique network addresses. Router works as the post office and network layer stamps the letters (data) for the specific destinations.
Protocols: These protocols work on the network layer IP, ICMP, ARP, RIP, OSI, IPX and OSPF.
Network Devices: Network devices including Router, Brouter, Frame Relay device and ATM switch devices work on the network layer.
Layer 2:Data Link Layer
Defines procedures for operating the communication links
Frames packets
Detects and corrects packets transmit errors
Protocols: Logical Link Control
• error correction and flow control
• manages link control and defines SAPs
802.1 OSI Model
802.2 Logical Link Control
Media Access Control
• communicates with the adapter card
• controls the type of media being used:
802.3 CSMA/CD (Ethernet)
802.4 Token Bus (ARCnet)
802.5 Token Ring
802.12 Demand Priority
Network Devices: Bridge
Switch
ISDN Router
Intelligent Hub
NIC
Advanced Cable Tester
Layer 1: Physical Layer
Physical layer defines and cables, network cards and physical aspects. It defines raw bit stream on the physical media. It also provides the interface between network and network communication devices. It is also responsible for how many volts for 0 and how many for 1. Physical layer also checks the number of bits transmitted per second and two ways or one way transmission. Physical layer also dealing with the optical, mechanical and electrical features.
Protocols: Protocols that work on the physical layer are ISDN, IEEE 802 and IEEE 802.2
Network Devices: Hubs, Repeaters, Oscilloscope and Amplifier works on the network devices.
OSI 7 Layers Reference Model
Introduction to TCP/IP
Here you will learn about Tcp ip network overview, data communication, ip addressing introduction, basic protocols, routing in the internet. TCP/IP short for Transmission Control Protocol is a suite of the communication protocols used to connect the hosts on the internet. TCP and IP were developed by a department of defense (DOD) in a research project to connect the number of networks by different vendors to form a big network of networks (the Internet).
It was originally successfully because of the services it gave, which everyone wanted to use such as file transfer, electronic mail, remote logon across a very large number of clients and server system. Several computers in a small network can use TCP/IP to communicate with each other. The IP component of the TCP/IP suites provides the routing between the two locally or remote computers.
IP forwards each packet based on a four byte, 32 bits address. TCP is responsible for verifying the correct delivery of data from the client to server. TCP also supports to detect the errors in the transmission and also triggers the data to retransmit correctly.
TCP/IP is a de facto standard of transferring the data on the network and on the internet. Each network operating systems that have their own protocols must support TCP/IP too. All the computers in a network must follow the rules to communication with each other.
TCP/IP stands for Transmission Control Protocol and Internet Protocol and it is a communication standard that defines how data travels on the internet and how network/communication devices communication with each other.
Inside the TCP/IP
TCP/IP is a not a single protocol but it is a suite of the protocols. There are the numerous protocols in the TCP/IP suite such as TCP, UDP, ICMP, DHCP, IMAP, HTTP, HTTPS, SSL, SMTP and many others.
Internet Protocol is a connectionless protocol that is used to communicate between the two computers. IP does not occupy the communication line between the two computers. With the IP communication, data is broken into the smaller pieces called packets, and these packets communicate between the two locally or remotely connected devices in a computer network or via internet. IP is also responsible for routing the packets to its destination. Routers are responsible for routing the packets towards its destination when a computer sends packets to an IP router. Data is routed towards its destination is all by a router. Router works as a post office.
TCP/IP
The TCP/IP (transmission control protocol/Internet protocol) work together in which TCP takes care communication between the application software i.e browsers whereas IP takes care of the communication between the computers. TCP breaks the data into smaller packets before they can be sent and IP sends the packets to the receivers.
IP Addresses
Each computer in a network or on internet must have a unique IP address before it can communicate with the other computer. The packets must have the address of the destination computers or devices. Each IP address is composed of 32 bits and 4 octets each packet must have an address before it can be sent to another computer.
This is an IP address 100.100.100.10 and this website http://www.example.com might have mapped with the same IP address. Without a unique IP address the communication on the internet is impossible. The numbers in the address must range between 0 and 255 in four period separated portions. Each IP address consists of 32 bits and 32 bits are consisting of 4 bytes. A computer byte can contain 256 different values e.g 00000000, 00100010, 00000111, 11111000, 01010101, 001100110 and up to 11111111.
Domain Names
Domain names are the unique identifier of a website because 12 digits numbers are difficult to remember. The name used for the web address is called a domain name e.g www.google.com, www.msn.com, www.yahoo.com all are domain names and comparatively are easy to remember instead of 12 digits numbers like, 123.220.44.240, 100.100.100.101 and 202.202.56.110. When you type a domain name in your web browser the domain name is translated into IP address by the DNS server, which is managed by your local ISPs or your corporate DNS servers.
All over the world a larger number of the DNS servers are connected with each other some are primary DNS servers, secondary DNS servers, Master DNS servers and Root DNS servers. When a new domain is registered by a domain registrar with associated TCP/IP address then DNS servers from all over the world are updated.
TCP/IP is a large collection of the different communication protocols.
TCP/IP is a large collection of different communication protocols.
A Family of Protocols
TCP/IP is a large collection of different communication protocols based upon the two original protocols TCP and IP. Each protocol in the TCP/IP suite is responsible for the different communication tasks. HTTP is responsible for the communication between the web server and the web browser. It sends requests from the client (browser) to web server and returning the web pages to the client.
HTTPS is responsible for the secure communication between the web browser and the web server. HTTPS usually handles the credit card transactions and other sensitive and secure data. SSL is responsible for the encryption of the data for the secure communication. SMTP (Simple mail transfer protocol) is responsible for sending the emails. MIME (Multi purpose Internet mail extension) is responsible for communicating the multimedia data such as, voice, video, graphics etc. IMAP (Internet Message Access Protocol) is responsible for storing and retrieving the emails.
POP (post office protocol) is used for downloading the emails from the email server to the personal computer. FTP (File transfer protocol) it takes cares of transferring the files between the computers. NTP (Network time protocol) is used to synchronize the time between the networks. DHCP (Dynamic host configuration protocol) is responsible for assigning the IP address dynamically to the network computers. SNMP (Simple Network Management Protocol) is used for administration of a computer network.
LDAP (Light weight directory access protocol) is used for storing the names and email addresses on the internet and also communicating with the Active directory in computer network. ARP (Address resolution protocol) is used to find the hardware address of a computer based on the IP address. Boot P protocol is used for starting computers in a network. PPTP (Point to point tunneling protocol) is used to make a secure tunnel in the private networks such as VPN.
TCP/IP is the Internet Communication Protocol.
A protocol is a set of rules, agreed upon methods or a communication language, which both computers understand and agree upon. TCP/IP defines the rules to communicate over the internet. Internet browsers and Internet servers uses TCP/IP to communicate on the internet
Web browsers, Web servers, Email programs and internet address all follow TCP/IP. An IP address is a part of the TCP/IP protocols.
Computer Network Protocols
The word protocol is derived from the Greek word “protocollon” which means a leaf of paper glued to manuscript volume. In computer protocols means a set of rules, a communication language or set of standards between two or more computing devices. Protocols exist at the several levels of the OSI (open system interconnectivity) layers model. In the telecommunication system, there are one more protocols at each layer of the telephone exchange. On the internet, there is a suite of the protocols known as TCP/IP protocols that are consisting of transmission control protocol, internet protocol, file transfer protocol, dynamic host configuration protocol, Border gateway protocol and a number of other protocols.
In the telecommunication, a protocol is set of rules for data representation, authentication, and error detection. The communication protocols in the computer networking are intended for the secure, fast and error free data delivery between two communication devices. Communication protocols follow certain rules for the transmission of the data.
Protocols Properties
Different protocols perform different functions so it is difficult to generalize the properties of the protocols. There are some basic properties of most of the protocols.
• Detection of the physical (wired or wireless connection)
• Handshaking
• How to format a message.
• How to send and receive a message.
• Negotiation of the various connections
• Correction of the corrupted or improperly formatted messages.
• Termination of the session.
The widespread use of the communication protocols is a prerequisite to the internet. The term TCP/IP refers to the protocols suite and a pair of the TCP and IP protocols are the most important internet communication protocols. Most protocols in communication are layered together where the various tasks listed above are divided. Protocols stacks refer to the combination of the different protocols. The OSI reference model is the conceptual model that is used to represent the protocols stacks. There are different network protocols that perform different functions. Following is the description of the some of the most commonly used protocols.
HTTP (Hyper Text Transfer Protocol)
Hypertext transfer protocol is a method of transmitting the information on the web. HTTP basically publishes and retrieves the HTTP pages on the World Wide Web. HTTP is a language that is used to communicate between the browser and web server. The information that is transferred using HTTP can be plain text, audio, video, images, and hypertext. HTTP is a request/response protocol between the client and server. Many proxies, tunnels, and gateways can be existing between the web browser (client) and server (web server). An HTTP client initializes a request by establishing a TCP connection to a particular port on the remote host (typically 80 or 8080). An HTTP server listens to that port and receives a request message from the client. Upon receiving the request, server sends back 200 OK messages, its own message, an error message or other message.
POP3 (Post Office Protocol)
In computing, e-mail clients such as (MS outlook, outlook express and thunderbird) use Post office Protocol to retreive emails from the remote server over the TCP/IP connection. Nearly all the users of the Internet service providers use POP 3 in the email clients to retrieve the emails from the email servers. Most email applications use POP protocol.
SMTP (Simple Mail Transfer Protocol)
Simple Mail Transfer Protocol is a protocol that is used to send the email messages between the servers. Most email systems and email clients use the SMTP protocol to send messages to one server to another. In configuring an email application, you need to configure POP, SMTP and IMAP protocols in your email software. SMTP is a simple, text based protocol and one or more recipient of the message is specified and then the message is transferred. SMTP connection is easily tested by the Telnet utility. SMTP uses the by default TCP port number 25
FTP (File Transfer Protocol)
FTP or file transfer protocol is used to transfer (upload/download) data from one computer to another over the internet or through or computer network. FTP is a most commonly communication protocol for transferring the files over the internet. Typically, there are two computers are involved in the transferring the files a server and a client. The client computer that is running FTP client software such as Cuteftp and AceFTP etc initiates a connection with the remote computer (server). After successfully connected with the server, the client computer can perform a number of the operations like downloading the files, uploading, renaming and deleting the files, creating the new folders etc. Virtually operating system supports FTP protocols.
IP (Internet Protocol)
An Internet protocol (IP) is a unique address or identifier of each computer or communication devices on the network and internet. Any participating computer networking device such as routers, computers, printers, internet fax machines and switches may have their own unique IP address. Personal information about someone can be found by the IP address. Every domain on the internet must have a unique or shared IP address.
DHCP (Dynamic Host Configuration Protocol)
The DHCP or Dynamic Host Configuration Protocol is a set of rules used by a communication device such as router, computer or network adapter to allow the device to request and obtain and IP address from a server which has a list of the larger number of addresses. DHCP is a protocol that is used by the network computers to obtain the IP addresses and other settings such as gateway, DNS, subnet mask from the DHCP server. DHCP ensures that all the IP addresses are unique and the IP address management is done by the server and not by the human. The assignment of the IP addresses is expires after the predetermined period of time. DHCP works in four phases known as DORA such as Discover, Observe, Request and Authorize
IMAP (Internet Message Access Protocol)
The Internet Message Access Protocol known as IMAP is an application layer protocol that is used to access to access the emails on the remote servers. POP3 and IMAP are the two most commonly used email retrieval protocols. Most of the email clients such as outlook express, thunderbird and MS outlooks support POP3 and IMAP. The email messages are generally stored on the email server and the users generally retreive these messages whether by the web browser or email clients. IMAP is generally used in the large networks. IMAP allows users to access their messages instantly on their systems.
ARCNET
ARCNET is a local area network technology that uses token bus scheme for managing line sharing among the workstations. When a device on a network wants to send a message, it inserts a token that is set to 1 and when a destination device reads the message it resets the token to 0 so that the frame can be used by another device.
FDDI
Fiber distributed data interface (FDDI) provides a standard for data transmission in a local area network that can extend a range of 200 kilometers. The FDDI uses token ring protocol as its basis. FDDI local area network can support a large number of users and can cover a large geographical area. FDDI uses fiber optic as a standard communication medium. FDDI uses dual attached token ring topology. A FDDI network contains two token rings and the primary ring offers the capacity of 100 Mbits/s. FDDI is an ANSI standard network and it can support 500 stations in 2 kilometers.
UDP
The user datagram protocol is a most important protocol of the TCP/IP suite and is used to send the short messages known as datagram. Common network applications that uses UDP are DNS, online games, IPTV, TFTP and VOIP. UDP is very fast and light weight. UDP is an unreliable connectionless protocol that operates on the transport layer and it is sometimes called Universal Datagram Protocol.
X.25
X.25 is a standard protocol suite for wide area networks using a phone line or ISDN system. The X.25 standard was approved by CCITT now ITU in 1976.
TFTP
Trivial File Transfer Protocol (TFTP) is a very simple file transfer protocol with the very basic features of the FTP. TFTP can be implemented in a very small amount of memory. TFTP is useful for booting computers such as routers. TFTP is also used to transfer the files over the network. TFPT uses UDP and provides no security features.
SNMP
The simple network management protocol (SNMP) forms the TCP/IP suite. SNMP is used to manage the network attached devices of the complex network.
PPTP
The point to point tunneling protocol is used in the virtual private networks. PPP works by sending regular PPP session. PPTP is a method of implementing VPN networks.
OTHER PROTOCOLS
VTP, ARP, IPX, OSPF, RARP, NFS, BOOTP, NNTP, IRC, RADIUS, Soap, Telnet, RIP, SSH.
Subnetting
Here you will find subnet network overview, ip addressing, address translation, network overview, subnet masking and subnetting overview. A subnet or a subnetwork is a separate part of an organization’s network. In a subnet all the machines are typically in one room, building or at one geographical location.
By dividing an organization’s network into the subnets allows it to connect to the internet by using the same shared network address. Without subnet’s an organization may get different connections to access the internet. Subnetting is the modification of a single IP network to create two or more logically different networks.
A subnet allows the flow of network traffic between hosts to be segregated based on the configuration of a network. Subnetting can improve the network security and performance by arranging the hosts into the different logical groups. Subnetting is required when one network address needs to be distributed across multiple network segments. Subnetting is required when a company uses two or more types of the network technologies like Ethernet and Token Ring.
Two network segments are restricted by distance limitations. Submetting or dividing the network into the segments is also required when localized network management is required for example accounting, sales, customer service departments. There is another reason for the subnetting, which is that the computers on the network, which use more bandwidth, needs to be separated from the rest of the computers. There are certain advantages and disadvantages of the subnetting. Before you start dividing your network into the different segments, you should assign the IP address to each computer in your network segment.
Subnetting makes the network management easier and it is also very helpful for the troubleshooting of a network segment. The internet is a collection of networks where users communication with each other. Each communication on the internet carries the source and the destination address of the computer. This address is called IP address. This 32 bit address has two parts: one part represents the network portion and the other part represents the host portion of the IP address. A company can use some of the bits in the machine or host portion of the address to identify a subnet. In this scenario, the IP address contains three parts: the network address, the subnet address and the machine address.
Subnet Mask Basics
The most recognizable part aspect of subnetting is the Subnet mask. A subnet mask contains 4 bytes, 32 bits and is divided into 4 period separated octets. Typically, a very common subnet mask in binary looks like this.
11111111 11111111 00000000 00000000
255 255 0 0
How to Apply a Subnet Mask
A subnet mask does not work like an IP address and it cannot exist separately without an IP address. An IP address and subnet mask work together to form a network. An IP address splits into two main parts when applying the subnet mask. The leftmost bits of a subnet mask must be set to 1. For example
11111111.00000000.00000000.00000000
11111111.11111111.00000000.00000000
11111111.11111111.11111111.00000000
The above example shows the valid representation of a subnet mask into the binary numbers.
00000000.00000000.00000000.00000000 is an invalid subnet mask.
11111111.11111111.11111111.11111111 is also invalid subnet mask.
All valid subnet masks contain two parts: the left side with all mask bits set to '1' (the extended network portion) and the right side with all bits set to '0' (the host portion), such as the first example above.
Subnetting an IP network can be performed for a variety of reasons such as using the different physical media in an organization, such as FDDI, WAN and Ethernet, preservation of the addresses and for the purpose of security, management and ease of troubleshooting. The most
common reason of the subnetting is to control the network traffic. In an Ethernet network, all computers in a segment see all the packets that are transmitted by all the other computers on the same segment.
In this situation, the network performance can be badly affected due to the heavy traffic loads, collisions and the retransmission of the packets. A router is used to connect the IP networks and it also helps to minimize the load of the traffic.
Subnet Masking
By applying the subnet mask to the IP address you can identify the network and host portion of the IP address. The decimal number 1 represents the network portion in the subnet mask and the node is represented the 0s. Performing a logical AND operation between the IP address and the subnet mask resulting in the network address.
For example, using our test IP address and the default Class B subnet mask, we get:
10001100.10110011.11110000.11001000 140.179.240.200 IP address of the class B
11111111.11111111.00000000.00000000 255.255.000.000 Default subnet mask of class B
--------------------------------------------------------
10001100.10110011.00000000.00000000 140.179.000.000 Network Address value
The following example shows the default subnet masks.
• Class A Subnet Mask- 255.0.0.0 - 11111111.00000000.00000000.00000000
• Class B Subnet Mask- 255.255.0.0 - 11111111.11111111.00000000.00000000
• Class C Subnet Mask- 255.255.255.0 - 11111111.11111111.11111111.00000000
Subnetting Review
Subnetting allows network and system administrators some flexibility in defining relationship among the hosts of a network. Hosts on the logically and physically different subnets can talk to each other through specialized devices called gateway or router. The ability to filter the traffic between
subnets can make the more bandwidth availability. Subnetting referred to as subdivision of a class based networks into subnetworks.
A router can exchange subnet routes with the other routers in the network. A subnetted network can’t be split into the isolated portion. All the subnets must be contiguous because the routing information cannot be passed to a non-network member. Router can exchange subnet routes with other routers within the network. Since the subnet masks are identical across the network, the routers will interpret these routes in the same manner. However, routers not attached to the subnetted network can't interpret these subnet routes, since they lack the subnet mask.
Therefore, subnet routes are not relayed to routers on other networks. This leads to our second
restriction. Subnetting allows you to create multiple logically different networks within the same class A, B or C. If you break a major network into smaller networks, it allows you to create a network of interconnecting subnetworks. Any device or gateway that is responsible for connecting the different subnetworks must have the distinct IP address one for each subnetwork.
To subnet a network use and extend the natural subnet mask using some of the bits from the host ID portion to create a subnetwork ID. In this example, given a Class C network of the IP address 4.15.5.0 which has a natural subnet mask of 255.255.255.0, you can create subnets in this manner:
11001100.00001111.00000101.00000000 204.15.5.0
11111111.11111111.11111111.11100000 255.255.255.224
---------------------------------|subnet|----
By extending the natural subnet mask to be 255.255.255.224, you have used three bits from the host portion of the mask and used them to make subnets. By using these 3 bits, it is possible to create 8 subnets. The remaining five ID bits of the host portion, each subnet can make 32 host addresses and the 30 addresses out of 32 are assigned to the devices or computers. The host IDs
of all zeros and all ones are not allowed.
204.15.5.0 255.255.255.224 host address range 1 to 30
204.15.5.32 255.255.255.224 host address range 33 to 62
204.15.5.64 255.255.255.224 host address range 65 to 94
204.15.5.96 255.255.255.224 host address range 97 to 126
204.15.5.128 255.255.255.224 host address range 129 to 158
204.15.5.160 255.255.255.224 host address range 161 to 190
204.15.5.192 255.255.255.224 host address range 193 to 222
204.15.5.224 255.255.255.224 host address range 225 to 254
GATEWAY
Here you will get the software and hardware network gateway overview and general introduction, basic configurations, software configuration, bandwidth, firewall overview and routing methods. Gateway is a network point that acts as the entrance point to another network. A gateway can be a hardware or software. On the Internet, a node or a stopping point can be a gateway or a host. A router also acts as a gateway. The computers that control and manage traffic and bandwidth within your company’s network or at the ISP are the gateway nodes. In the enterprise network the gateway node acts as a proxy server and a firewall. The gateway is also associated with a router and a switch.
A network gateway is an internetworking system that joins two networks together and it can be configured in software, hardware or both. Network gateway can operate at any level of OSI layers model.
CONFIGURING THE GATEWAY
The gateway has two sides: The WAN side connects to your cable DSL modem and LAN side connects to your private network via a hub or switch. The main function of it is to route the traffic from computer to the Internet and back to the computer. A computer with the two NIC cards can act as a gateway. It routes the network traffic between two logically and physically different networks.
In its configurations, you first configure the public side of the gateway and the IP address, which is assigned to you by your ISP. The public side configurations generally includes, assigning the IP address, DNS server, subnet mask, ISP gateway IP address and host name. Additionally, if your ISP uses PPPoE, you simply have to enable PPPoE in your gateway.
On the other hand to configure the private side , you have to enable DHCP. By enabling this feature each computer in your network, will automatically pick the settings from the DHCP server that are required for a computer to be a part of the network and communicate.
SOFTWARE CONFIGURATION
The last step in the configurations, is to configure each PC in such a way that it automatically gets the all the settings from the DHCP server. Make sure that TCP/IP protocol is properly installed in each computer of your network. After configuring each PC in your network perform a reboot.
After rebooting the each PC in your network, you will see a blinking underneath network icon on the right side of the task bar. If everything is done then you can access the internet, share the printer and data in your network.
The firewall can also be configured with it to put a check on the unauthorized network traffic from the internet to your computer or network.
Network Routing
You will be able to find the basic network routing overview, router configuration, router working, simulations static routes and routing table. Routing is the process of defining routes for the packets to its destination through an internetwork and this is performed by the router.
Routing is consist of two separate tasks.
1. Defining paths for the packets through and internetwork.
2. Forwarding data packets based on their predefined paths.
Generally, there are two types of routing.
STATIC AND DYNAMIC ROUTING
Routing can be performed by manually defining the routes or paths for packets to reach its destination. This is called static routing.
Stating routing works well for the small networks and when using the static routing, the routing table of the each router should be updated each time there is any change in the network configuration or topology. A router, whose routing table is not regularly updated, cannot communicate with the other routers.
While on the other end in most of the networks, routing is accomplished through the use of the dynamic routing. In the dynamic routing, routing protocols, such as RIP, OSPF etc create and maintain the routing tables of each router. Practically, dynamic routing functions very well than the static routing
ROUTING TABLE
A routing table is a set or rules, viewed in a tabular format and this used to define the routes of the data packets. All the network devices, which have IP, enabled functionality such as routers and switches use the routing tables. Routing table stores the information and configurations of every router in the IP enabled network. A routing table contains the information necessary to transmit the packets toward its destination.
When a packet is received, the network devices matches the information contained in the packets and the information in the routing tables and then it defines the shortest possible route for the transmission of the packets towards its destination.
Each packet contains the information of its origin and destination and the routing table contains the following information.
• Destination: The IP address of the packet’s final destination (next hop). Next hop: The IP address to which the packet is forwarded
• Metric: It assigns the cost to each route so that most-effective paths can be picked up.
• Routes: It includes directly attached direct subnets, indirect subnets, that are not directly connected to the device but it can be accesses through one ore more hops
• Interface: The outgoing network interface the device should use when forwarding the packet to its final destination.
Routing tables can be maintained manually by the network administrator or by dynamically (automatically). The static network tables do not change unless the network administrator changes them. Routing tables can be maintained manually or dynamically. Tables for static network devices do not change unless a network administrator manually changes them. In the dynamic routing, the network devices such as routers and switches maintain the routing tables dynamically by using the routing protocols, such as RIP, OSPF etc. In the dynamic routing, the network devices listen and detect any network or devices failure and packet congestions.
Routing in the Internet
Routing is the method in which data finds its destination from one computer to the next. In the Internet there are 3 major aspects of routing.
1. Physical Address Finding
2. Determination of inter-network gateways
3. Numeric and symbolic Addresses
Physical address finding is the method of the Internet Routing and is used when datagram is transmitted from a computer. It is necessary to encapsulate the IP datagram. This encapsulation requires the local network or physical address.
If a computer wishes to transmit IP datagram it needs to encapsulate the physical address of the destination network device in the frame. This address can be achieved by using the table that will map the IP address with the physical address. Such table can be configured into a file that can be read into the memory at the boot up time. Computer normally uses the Address Resolution Protocol (ARP), which operates dynamically to maintain the translation table.
The second method is necessary because the Internet consists of a large number of local networks, which are interconnected with each other by gateways. Such gateways are known as routers, which has physical as well as logical connectivity with many networks.
The determination of the best suitable gateway and port for a particular IP address is called routing.
The third method generally involves the translation of the human friendly form (names) to the number address (IP Address). IP address can’t be remembered due to its numeric form but the simplest names (domain names) are easy to remember e.g www.yahoo.com, www.google.com, www.msn.com are easiest to remember as compared to the IP addresses 122.11.22.34, 223.45.66.76, 155.44.55.120. DNS translates the domain names into the IP address and IP address into the domain name. This domain to IP translation is a must for communicating on the Internet because communication on the Internet is performed by the IP addresses.
Communication between routers
The Internet is a network of networks. The Internet consists of large number of autonomous systems, each of which further consists of routing domains. Such autonomous systems are usually run by the larger companies or universities. Within the Autonomous system, a router communicates with the other router using the best intra domain routing protocols, which are known as interior gateway protocols. Autonomous system are connected via gateways, these exchange information using inter domain routing protocol, which are also called exterior gateway protocols.
The RIP or (Routing Information Protocol) is the commonest interior gateway protocol and the recent protocol such as open shortest path first (OSPF). The purpose of these protocols is to enable routers to exchange locally so that all the routers in the autonomous system must a have coherent and up to date information.
When a host receives the new routing information, it is likely to update not only to it but also sends this new updated information to all the connected hosts so that they can updated themselves. Hence these changes propagate across the entire network.
Internet Fax Services
Here you will learn internet fax server overview and general introduction to the online faxing methods, how to send a fax and online services. A fax server consists of these things a PC, which is connected to the LAN, Fax server software installed on the PC and a Fax modem or a Fax board. Fax messages can be stored as printable documents, spread sheet, database or graphics. When someone wants to fax the documents, they can print the document to the fax printer then put the recipient information such as name and fax number, select the cover letter, type your message and then send the fax through the faxing software installed on your PC.
Alternatively, you can send the fax to the email messages and can take the fax number from the outlook express contact’s list. Sending fax through PC typically takes less than 30 seconds.
Alternatively, fax server can also be setup to receive the faxes and after receiving the faxes, these can be sent to the printer machine or can be sent to the specific recipient’s email address to notify them that he/she has received a fax.
There are certain advantages of the PC fax server, which I have discussed as follows.
1. The main feature of the Fax server is that it saves your time and cost and you can send the fax in the same way as you send emails and attached the fax to send to the recipients.
2. Invoicing, purchase orders and requested information can be scheduled to be faxed to the intended recipients.
3.Fax server will also retry if the recipient number is busy or if there is any error in the number.
4. You can also save the fax numbers of the frequent users.
5. Fax books also make it easy to send the faxes to the groups of people and at the scheduled times.
6. The faxes that are sent directly through the PC are looks better in terms of the resolution.
7. You can also manage the fax server to redirect the receiving faxes to the appropriate recipient so ensuring the security and timely receiving of the faxes.
8. The administrators can automate many functions of the fax server. A fax server can be configured to automatically send the invoices, purchase orders and the promotional newsletters. Additionally, a fax server can work without papers and reduces the overhead of putting and checking the papers again and again. Fax messages can be stored in your PC.
What is a Internet Fax
Internet fax is a device that uses IP networks to transmit the faxes instead of the PSTN. Internet fax uses e-mails as the medium for sending the faxes. Internet fax services include email to fax, fax to email and PC to fax (sending faxes from your computer). Internet fax is type of service, which enables you to send and receive the faxes in a timely manner without a fax machine. Only an email accounts is required to setup your Internet fax account.
Subscribers have to monthly fees to the internet fax service providers. Internet fax service providers usually works in a way that when a fax is sent to the subscriber’s number, the fax service receives the fax and send it to the recipient’s email address as an attachment.
All you need is to have the registered email address with the internet fax service providers. You have to write the fax content in the body of the email and type the fax number in the “To” field with a @ sign and a internet fax service name e.g 14545668999@efax.com. In the subject field sender can write the name of the recipient.
There is a small tool bar in the system tray for sending and receiving the faxes and it comes after installing the fax software. Upon receiving the email to the Internet fax service providers the automated programs convert the email messages to the fax format and send the fax to the recipient fax number. On the other, hand the recipient receives the fax on their fax machine normally.
The Internet fax services provide very ease and you assigned a fax number, which has to be active 24 hours so that you account can accept the faxes. On the other hand, the working of the regular fax machine is typically depends on your telephone line, which should be free while sending and receiving the fax. Internet fax service also saves your papers and the need of the fax machine.
Internet fax service is very familiar to the sending and receiving the email messages and it also saves the cost and time so many people are likely to use this service.
Another big advantage is given by the Internet service providers is that it offers the toll free numbers to its subscribers in USA and Canada. So the people from USA and Canada can send faxes for free. Most internet fax services costs $10-20 per month. The communication charges are greatly reduced as opposed to the conventional fax machines, which costs a user per page.
Windows Firewall
Windows firewall is a protective layer or boundary that monitors the in and out traffic from your network and internet. The firewall is a protective and defensive boundary against the intruders and unauthorized persons. You can enable the firewall in XP Professional with these simple steps.
1. Click Start > Settings > Control Panel
2. Windows Firewall > Double click.
Network Troubleshooting Tips
If you find a communication failure error in the TCP/IP network then try to find and troubleshoot the errors with the following methods.
1. Make sure you can ping the other computer by name.
2. Make sure you can pint the other computer by IP address.
3. Make sure you have assigned unique IP address and computer name to all the computers in the network.
4. Make sure you have assigned the correct gateway, subnet mask, DNS and DHCP addresses.
5. For troubleshooting purpose try to uninstall any firewall software and see if the problem is resolved.
Windows Network Security
Security a computer network should be the top priority of the network administrators, system managers and security specialists. You can secure your computer network by doing these things such as installing the updated operating system, up-to-date antivirus program, event log monitoring, encryption, group policy management, patch management, security scanners, auditing, firewall security, web application security, web content filtering and controlling the access to only the authorized users.
What is a Web Server?
Learn Web server software overview, how to configure, how it works, apache, tomcat. Web server is a computer including a software package that provides the specific services to the client computers. Web server delivers the web pages. Every web server has an IP address and a domain name. If you sends a request through your browser for this website http://www.networktutorials.info, the request goes to the server whose domain name is networktutorials.info.
The server fetches the index or main page of the website and sends it to your browser. Web-based servers are used for hosting the websites. One web server can hosts thousands for one sites. But in the hosting companies there are number of the web servers for load balancing and sharing the other services.
A computer can be act as a web server by installing and configuring the server software and connecting the computer to the Internet. Normally, web server computers have to be turn on (online) for almost all the day.
There are many software applications that are used as the web server like IIS, Apache web server, Tom Cat web server. A web server typically accepts thousands of the concurrent incoming requests for the specific domain, that it hosts.
In case if the server is down for any reason, the websites that are hosted on this server cannot be accessed. So the downtime is a biggest negative thing for the web hosting companies. Many hosting companies have to mention the uptime of their servers for the client’s satisfactions like 99.9 % uptime. You may have seen this percentage on many hosting companies’ websites.
The web servers serves the objects in the form of html documents, plain text, images, sounds, video and some other form of the data. Many of the data types may not be placed in the static form but they are shown on the run time by the software programs, that are installed on the web server and the CGI scripts are the most common form of these programs.
Web servers and the browsers such as internet explorer, Firefox, Netscape, Opera etc communicate with the web server by using the HTTP protocols (Hypertext Transfer Protocol). This is very effective method of requesting the data over the Internet. Web servers are in various shapes and sized and run under different operating systems like Windows, Linux, and Unix etc. They are also range differently in prices and working.
Apache Web Server
The Apache web server is the most popular and most commonly used web server today. Apache web server has many features and good functionality that appeals to the users and that’s major cause of its popularity. On the other end, Microsoft’s IIS still is struggling to complete fully with apache web server. IIS is a very good server on the NT platforms and Apache is compatible with the Linux/Unix platforms.
Another big reason for the worldwide acceptance of the Apache web server is its stability. Many big websites on the Internet has chosen Apache web server for their hosting needs.
Additionally, Apache web server is a relatively fast. If your website contents are static then Apache’s working is very efficient and fast and on the other end, if you are using scripts like CGI scripts or others, it usually slows down the speed of the Apache web server.
A Web server is simply a little piece of the software, it takes the file name sent in the GET command, retrieves that files and send it back to the browser.
Most servers implement some level of security on the serving process. For example login/password accessible page requires the proper login and password from the users to accept that page. Web servers have the database and login information of the entire subscriber and only a subscriber of that typical service will be able to see that page. Additionally, while doing secure transactions the web pages allows encrypted transactions between the browsers and the servers such as on the E-commerce websites and other websites where a transaction through a credit card is required.
Basic Overview How Web Server Works
A web server performs various tasks on the request from the clients. To understand the working of the web server, it is necessary to first understand that what is client and server and what is their relationship with each other. A client is a program that sends request to a server and server responds to the requests of the clients.
This generic definition covers many types of relationships between client and servers like database server & web server etc. Web server have to be connected to the internet because client computers need to access them for various needs like data, files, graphics, video and html documents access.
The client program such as browsers and typically designed for the purpose of communicating with the web servers. A browser itself has different levels of features and security. To start the communication between the client (browser) and the server, a set of rules or agreed upon way is required and that is called a protocol. To access the web pages from the server HTTP protocol is required and for the file sharing access FTP protocol is required. There are a large number of the web protocols.
A web server is configured and designed in such a way that it responds to the thousands of the concurrent incoming requests from the clients for different things like html documents, graphics, images or video etc.
Windows Networking
What is Windows Networking?
The term networking covers a broad range of the topics and technologies. A computer network is segmented into different parts to share the data and resourced between the different computers of a network. Microsoft has released the operating systems that have the networking capabilities so Microsoft Windows 98, Microsoft Windows 2000, Windows 2003, Windows XP Professional and Windows Vista all are the network operating systems.
All these operating systems have built inn capabilities of files and printer sharing, security, network administrative control, protocols support such as TCP/IP, NetBIOS, IPX/SPX and network hardware support.
Naming Computers
All computers in a Windows based network requires a unique name for their identification i.e. the name of the computer A cannot be assigned to the computer B and so on. Assign a meaningful computer name to all the computers and the name should be easy to remember.
All the names should be configured properly and ensure that the name is not longer than the 15 characters and they contain no spaces in them. Also try to avoid the special names while naming the computers such as / \ *,:,. To assign a computer name in Windows XP and Windows 2000 do the following things.
1.Right click on the My Computer.
2. Click Properties
3. Click on Computer name.
4. Assign a unique and meaningful computer name.
Naming Workgroup and Domains
A Windows based computer network can be a workgroup (Peer to Peer) or domain (client/server). You can make your computer a part of the workgroup or a domain. If you have centralized server then your computer will be part of the domain and if you have no server then all computers will be having peer to peer networking. In both cases, while joining your computer to a domain or a workgroup always assign unique, sequenced, memorable and meaningful names to the computers. Do not use duplicate names and the special characters such as / \ *,:,,. In order to join a computer to a domain or workgroup in Windows 2000 and Windows XP Professional do the following.
1. Right Click on My Computer
2. Click Properties
3. Click on Computer Name
4. In Workgroup or domain, enter the name of the workgroup or domain.
If everything is correct such as unique computer name, unique IP address, correct workgroup or domain name then you computer will be the part of the workgroup or domain in the few seconds and you will be see a welcome to domain or workgroup message and will be prompted to restart the computer name.
Files Sharing
Being on network computer files and printer sharing is a must. To enable the files and folder sharing in Windows XP Professional 2000 and Windows 2000 do the following.
1. Right Click on the folder name you want to share.
2. Click on the properties.
3. Click Sharing.
4. Click on Share this computer on the network.
5. Assign a shared computer name.
You can set the sharing rights for the users and also control the shared folder access by allowing and denying permissions to specific users or groups. If you want to share the individual files, you can put the files in the same shared folder. All the files and folders in the parent shared folder will be automatically shared.
Network Cable Errors in Windows
If your computer network cable is not working properly, you will see a repeated message or pop up “network cable is unplugged” on your desktop and the blinking status lights of the network will also stop blinking. There can be many causes of this problem and you can fix this error with these simple tips. If you have another Ethernet adapter installed but not using it, then disable it by right clicking on the monitor icons on the right side of the desktop and select the disable option. Check both ends of the cables and ensure that the RJ 45 connectors are properly inserted in the LAN card and in the Hub/Switch. Update the drive of the LAN card from the vendor’s website and if the problem still exist then replace the cable with new one. If the problem is still not resolved then replace the LAN card with a new one and try to use a new hub or switch and put cable’s one end into it. By these simple steps, you will be able to trace out and troubleshoot the problem.
VOIP Network
Introduction to voip network, how internet telephony works, how to make internet phone calls, and what actually is voice over internet protocol. VOIP is simply a transmission of the voice traffic over IP networks. VOIP is a family of technologies, in which IP networks are used for the voice applications and traffic e.g IP telephony, voice chat and teleconferencing.
VOIP gives solution at almost every layer of the IP network. The Internet Protocol was developed and designed for data communication. The success of the IP network has led to its adaptation to voice networking.
Voice over internet protocol is the fast emerging and replacement technology for the voice communication. Many people still want to know that how it works. Voice over internet protocol costs less than your regular phone service and for this reason it’s more attractive to the consumers. VOIP also costs less than a mobile phone’s monthly cost.
In the fast communication age, the number of the VOIP providers is increasing. As the number of the VOIP providers grows it gives the more options and calling plans. The VOIP service is available for both residential and commercial use that ranges from PC-to-PC service and PC-to-Phone and Phone-to-Phone. The following are the most common and basic features of the VoIP.
VOICE OVER INTERNET PROTOCOL FEATURES
The major feature of the VoIP is that the customers can make call to everywhere in the world. Only the broadband internet connection is required. The customers can take their IP phones with them on the national trips as well as on the International trips. Among the other features of the VoIP are the soft phones, which is a software application that loads onto the computer and is used to make the phone calls. The interface of these softphones is similar to the telephone. By these software phones, anyone call make phone calls to everywhere in the world if broadband internet connection access is available.
The most VOIP services also gives the access and options of call waiting, caller id, call transfer, repeat dialing and three way dialing features. There are some additional features like call filtering, forwarding a call or sending a call to the voice mail, but the service providers may charge additionally for these services. Most VoIP service providers allow the customers to check their voicemail or attached messages to an e-mail by connecting to the web.
The facilities and the components of a VoIP phone system that are supplied by the VoIp providers and phone operators are generally vary with each other. The users should be aware of the pros and cons of the VoIP services before subscribing. Also, the customer should also check the availability of the 24/7 cutomer support that may be required fro the VoIP hardware as well as software configurations and for other technical issues.
How IP Telephony Fits In
Among the other names in the VoIP industry, the Skype and Vonage are the biggest names and all the credit for the growth of VoIP goes to Skype and Vonage. There are a large number of other vendors for the telecommunication industry that have promoted the “IP telephony”. As well as the Cisco Systems and Avaya were two of the earlier names in the VoIP phone system technology. The have paved the way for the growth of VoIP technology. More and more residential customers are using the VoIP service likewise the corporate customers are integrated the IP based-voice technology and upgrading their IP networks to support the VoIP technology. This transition is similar to the move from mainframe computers to the personal computers a couple of years ago
HOW DOES VOIP OVER INTERNET PROTOCOL WORKS
Voice Over Internet Protocol also called Internet Telephony and internet telphony is the technology fo future. With this technology you can make free of cost and very cheap long distance calls all over the world. VoIP uses a broadband Internet connection for routing telephone calls as opposed to the switching and fiber optics. By this process the customer can get the higher efficiency and quality of service as well as low cost. One major and interesting aspect of the VoIP technology is that there is no major infrastructure is required.
The VoIP infrastructure includes the broadband Internet connection, regular telephone line and VoIP software and hardware. Some of renowned companies of the voice over internet protocol business are Vonage and Skype. These both companies prove services to their US people as well as people of the other countries. Cisco systems has also a big name in providing the VoIP hardware
ISDN Line
Find here ISDN Network, introduction to ISDN line, bri, t1 lines, d1 lines, primary rate interface, connection time and setup instructions. The regular phone line, which is used at home and offices is an analogue phone line. Your voice is picked up by telephone mouthpiece and then sent down the phone line as an analogue wave. Regular modem converts the digital signals of the computer into the analogue waves, which then travels on the regular phone lines. At the other end, modem receives that analogue signals and then convert back into the digital signals that are understandable by a computer
ISDN network is a digital communication system that is capable of producing the maximum transmission speed of 1.4Mbps. 128Kbps speed is however more common in the digital technology. It's a international standard for sending data, voice, video over regular digital telephone lines. ISDN uses UTP (unshielded twisted pair cable) for transmission.
Types of ISDN Network
There are two basic types
• Basic Rate Interface (BRI) – It consists of two 64 B-channels and one D-channel for transmitting control information.
• Primary Rate Interface (PRI) -- It consists of 23 B-channels and one D-channel (for U.S.) or 30 B-channels and one D-channel (for Europe).
The actual version of ISDN employs base band transmission. Another version, called B-ISDN, uses broadband transmission, which is able to support transmission rate of 1.5 Mbps. B-ISDN mainly requires fiber optic cables.
To access the B channel, it is necessary to subscribe the ISDN phone line. Customers are also required to have some special ISDN devices, which are known as terminal adapters, which are used to communication with the telephone company switch or other ISDN devices.
How ISDN Works
In an analog network, a regular telephone line that is provided by the telephone company supports a single transmission channel, which normally can carry only one service, voice, data or video at a single time. With ISDN, this same pair telephone line is logically divided into the multiple channels. A typical line has two channels.
The first type of channel is called B channel. This channel can carry about 64Kbps of data. Typical ISDN line has 2 B channels. One channel is used for voice and other channel is used for data communication. This data/voice transmission process occurs on the regular one pair copper wire.
The second type of channel is used for link and call setup. This channel is known as D channel or Delta Channel.
The third channel has only 16Kbps of bandwidth.
Advantages
Speed
There is an upper limit of the speed in the commonly used dial up modems, which is 56kbps. But due to the quality and other factor, the maximum attainable speed is 45kbps.
ISDN allows multiple digital channels to operate simultaneously through the same regular one pair copper wire. If the telephone company supports the digital connections then a change can occur. The digital signals instead of the analogue signals, transmitted across the telephone line. In the digital scheme, there is much more data transfer rate than the analog lines.
Multiple Devices
A separate telephone line is required for using the fax, telephone, computer, router and live video conferencing systems. A separate line is required for each device. ISDN network lines can handle the multiple devices on the single line. Up to eight devices such as, computer, faxes, cash registers, credit card readers or other devices can directly be connected to a single ISDN line, all these devices can work simultaneously.
Connection Time
V.34 modems typical take 30-60 seconds to establish a connection and on the other end an ISDN call usually takes less than 2 seconds to establish a connection.
Disadvantages
There are some disadvantages of the ISDN lines, which I have discussed below.
1. ISDN is more expensive than the Plain old telephone system.
2. The telephone company and the ISDN user both are required to have the specialized digital devices.
ADSL VS ISDN
There is a noticeable difference between the two services.
• ISDN provides two voice channels or one 128Kbps data channel while ADSL is basically a data pipe.
• The power for ADSL is sent by carrier over copper wire; as with the local phone service. The line works even when local power fails. This is an advantage over the ISDN lines, which requires the local power supply.
setup the Gateway Device
Gateway device – There are different gateway devices available from different companies like
dlink.com, linksys.com, netgear.com and Cisco systems. Each device has difference setup configurations but the basic purpose of all these devices is the same.
The Gateways have a number of common features and functions such as NAT (Network Address Translation) that translate your public IP address into the private IP address on your network, DHCP server, PPP. Before buying any gateway device, make sure gateway device must have all these features.
Some advance gateways have the following features.
• wireless access point
• VPN
• print server
• DMZ (make one PC available to the Internet but still protect it through the firewall
• multi-port
• Content filtering
Most advance gateways comes with integrated hubs or switches and if your gateway don’t have the functionality of a hub/switch then you will have to buy a hub/switch for your home network. Before buying a hub/switch you should consider the two main things 1. it should support dual
speed i.e 10mbps and 100mbps and 2. it should have maximum available ports.
Cat5 cable – For setting up a home network, you will need a several pieces of the CAT5 Ethernet cables. These cables can be used in the different scenarios like for connecting the two PCs (if you have a two computer network) and if you have more than two computers then each computer will be directly connected with the hub/switch or gateway device. The most commonly used cable for computer networking is Cat5 cable.
Once you have all the required things like cables, hub/switch, LAN cards etc. then install a network card in each PC. You must make sure that each card is properly installed and is not showing any signs of conflict with the other network devices.
How to connect two computers wirelessly
In some recent years, wireless networking solutions have became very popular. There are several wireless technologies exists to support the wireless networking.
These technologies include Wi-Fi, Bluetooth and infrared.
Wi-Fi connections can reach at a greater distance than the other wireless solutions that are mentioned above. Many new PCs and Laptops now have the built-in capability of the Wi-Fi. Wi-Fi can be used with or without network fixture. In the two computers Wi-Fi networking minus a fixture also called ad-hoc Wi-Fi.
Bluetooth technology supports high speed wireless connectivity and communication between the two computers without the need of a network fixture. Bluetooth is commonly used when networking a computer with the consumer’s cell phone or handheld device. Bluetooth works well if both the devices are in the same room or location. While networking among the handheld devices consider the Bluetooth technology solution.
Infrared networking exists before the Wi-Fi or Bluetooth technologies on the Laptops. Infrared wireless connections only work between two computers and do not require a fixture. Infrared networking is relatively fast so consider using it if your computer supports it and you don’t have
the Wi-Fi and Bluetooth features in your computer.
Home Computer Networking-Basic Setup
Here you will get the basic Introduction Home Computer Networking-Basic Setup, wireless access point, lan troubleshooting, lan connectivity, dsl modem, gateway device, vpn and wi-fi. Computer Networks exists for more than 30 years and only recently they have become more popular at home both in forms of wired and wireless networking. Now many computer literate people from all over the world wish to have a computer network at home. There are many advantages and usage of a network, which we have described in the other sections of this website.
Millions of people have adopted the home network and now they are looking for the more advanced technology in the home networking and that is “wireless home networking”.
We will discuss the various basic and advance aspects of the home networking considering that no prior knowledge of the network technology. We will briefly explain the setup, troubleshooting, installation, network devices used and other aspects of the home networking.
Today in the age of Information technology, it’s not difficult for someone to have more than one PCat home.
If I apply this situation to you (that you have more than one computer at your home) then most probably you would wish to have access on the data and resources like, hard disk, printer, modem of the other PC and you can even access the broadband Internet like DSL or cable modem and you can also play a multi-player network game. All this is possible by just connecting and configuring the two computers at your home. There are several ways to do the home networking but all it depends on budget, security needs and nature of your work
Your cable/DSL modem plugs straight into the computer. The computer is exposed to the public Internet (indicated by the color red). There is no connection for more than one computer. You only have one IP address from your ISP.
If you have a broadband Internet connection at your home like DSL or cable net then you can share your internet connection with more than one PC at your home by installing the network card in each PC and configuring the hub/switch or a router.
If you have two PCs at your home and you want to share your internet connection with the other computer then you can simply share the internet connection by following these steps.
1. Connect two PCs with CAT5 cable and make it a cross over cable.
2. After connecting both the PCs, assign a different IP addresses by going in the properties of the LAN card like 100.100.100.1 and 100.100.100.2 or you can assign any other IP address. (Please note that these IP addresses that you use for your home networking are the private IP addresses and they have nothing to do with the IP address that are used on the internet (public IP addresses).
3. After assigning the IP addresses install software on the computer one, which will be used for sharing the Internet connection and this will be called proxy software (and your computer one will act as a Proxy Server). The more common proxy software is Wingate, Win Proxy and Internet connection sharing (ICS). ICS is by default installed in Windows operating systems and can be configured separately.
Internet access by using a hardware router/gateway/firewall device
In this situation, you have to install a hardware router, which will be act as a gateway. Your router will be connected with the public IP address, which will be assigned to your by your ISP and hub/switch will be attached to the router. All the other PCs in your home or small network will be directly attached to that hub or switch.
Network Security
You will find here network security overview, networking solutions, anti virus, anti spamming tips, trojan horses, malware, adware. Security is an essential element in maintaining any network. The main focus of the IT managers and computer network administrators is to secure the computer networks.
Users are happy to get the data on time and without any problem. The use of the authentication and biometrics can improve the security to some extend. Computer Security in the data communication cannot be compromised. Hackers’ can exploit the sensitive and financial and corporate data. There can be many threats to a computer network and it’s the responsibility of a computer network administrator to keep the computer network secure from these threats.
IT Administrator should know about all the possible security attacks and also know their solutions. IT Administrator should look for the viruses from the Internet, Malware, Adware, Trojan horses, E-mail attachments, Floppy disk, CD or any infected computer that is attached to the network. Spyware and network intrusions are specifically designed to get the secret information from their target companies, which can do harm for the company. Everyday security threats are refined as hackers designed new security threats.
The main cause of a security threat in the small companies is the misuse of the internet without proper anti virus, anti spyware installed on the every PC of the company’s network. For example if a company’s employees browse an inappropriate website, sends or receives the infected data, leaks company’s secret information, then there are greater chances for a possible virus/malware attack.
In my opinion, the end user’s education on the security threats, preventions and precautionary measures are must. They should be trained about the possible and easy virus attacks from the internet if they browse the inappropriate sites.
Another important thing is the insider’s attack e.g if the company’s employee leave the company for any reason, then its very important that all the computer and other company’s sensitive assets access should be revoked by him immediately. I have personally seen a situation, when a company’s network administrator was dismissed and he access the company’s server by VPN and send harmful viruses to the server and the entire computer network, and it was impossible for the IT manager to control all the security attacks in one time.
It’s the responsibility to keep a closer eye on the new employee’s activities, their access to the sensitive data, and computers servers. IT managers should bring it in the knowledge of the employees that any change in their computer will be logged. So that nobody can even try to do anything that is not permitted.
There are six basic security steps for the Windows platforms. If a network administrator can follow these steps then he/she can save the computerss from all the possible security threats and virus or malware attacks.
First the IT managers should divide the computer network into the segments. They should filter the access to the internet with the help of a firewall by blocking TCP port 1433 and TCP port 1434. Internet access from the outside should be allowed to the SQL systems. All the unwanted ports should be blocked and only the required ports should be open for access.
Second, moderate the affect of the spoofed ports. The port 80 is the most commonly used port.
Third, as network administrator you should install the current patches to you’re your server computer and client’s up to date. Patches can prevent the systems from the known vulnerabilities. Latest patches can be downloaded from the Windows website. You can also configure to automatically update. Also third party patches products are also available that can be tested and installed. Additionally, by strengthening the user authentication process can be very helpful for security purposes.. You can use password security and other technological methods for the authenticate purpose.
Fourth, you can limit the number of the network administrators it can also be helpful for security a computer network. Admin rights should not be given to the local PC, until and unless it is the requirements for the applications that are installed on the local PCs.
Fifth, protect computers against the known attacks. Don’t disable any Windows known service such as clipbook, Telnet etc. Set the powerful permission the shared network resources.
Last, you can configure the security policies. Implement the security policies on your network.
Security measures and methods have expenses with their purchases. Deployment, maintenance and the implementations of these methods can increase the security cost. Some other things which a IT administrator or a IT manager should keep in mind are the education of the employees about the security, use of the encryption and digital right management software, block the unwanted emails and audit security on the regular basis. Network security methods should be used and implemented in order to prevent your computer network from the unauthorized access.
In this article You have discovered the Computer Network Security Overview More topics to come are Cisco Labs, Routing, IP addressing & Free IT resources.
WAN Configurations Commands
Networking over WAN is the main functionality of a router. The most common use of a router is for the WAN connectivity. Here is a list of the commands for the different methods of the WAN connectivity.
PPP Configuration
Point to point protocol is a method for the WAN connectivity and you will find here some commands of PPP.
encapsulation pppppp authentication
ppp chap hostname
ppp pap sent-username
sh int ser 0 - use to view encapsulation on the interface
Frame-Relay Configuration
One of the methods for the WAN connectivity is the Frame Relay. Find here some basic commands for the WAN connectivity through Frame Relay.
encapsulation frame-relay ietf - use IETF when setting up a frame-relay network between a Ciscorouter and a non-Cisco router
frame-relay lmi-type ansi - LMI types are Cisco, ANSI, Q933A; Cisco is the default; LMI type is auto-sensed in IOS v11.2 and up
frame-relay map ip 3.3.3.3 100 broadcast - if inverse ARP won't work, map Other IP to Your DLCI # (local)
keep alive 10 - use to set keep alive
sh int ser 0 - use to show DLCI, LMI, and encapsulation info
sh frame-relay pvc - shows the configured DLCI's; shows PVC traffic stats
sh frame-relay map - shows route mapssh frame-relay lmi - shows LMI info
Miscellaneous Commands
In the last but not least here is a list of the some miscellaneous and useful commands
sh controller t1 - shows status of T1 lines
sh controller serial 1 - use to determine if DCE or DTE device
(config-if)#clock rate 6400 - set clock on DCE (bits per second)
(config-if)#bandwidth 64 - set bandwidth (kilobits)
Routing Protocols
RIP, IGPR and OSPF are the routing protocols and here is a list of the commands for the working on the routing protocols.
Configure RIP:
router rip
network 157.89.0.0
network 208.1.1.0
Other RIP Commands:
debug ip rip - view RIP debugging info
Configure IGRP:
router IGRP 200
network 157.89.0.0
network 208.1.1.0
Other IGRP Commands:
debug ip igrp events - view IGRP debugging info
debug ip igrp transactions - view IGRP debugging info
Access Lists
Here is a list of the Access list command of a router.
sh ip int ser 0 - use to view which IP access lists are applies to which int
sh ipx int ser 0 - use to view which IPX access lists are applies to which int
sh appletalk int ser 0 - use to view which AppleTalk access lists are applies to which int
View access lists:
sh access-lists
sh ip access-lists
sh ipx access-lists
sh appletalk access-lists
Apply standard IP access list to int eth 0:
access-list 1 deny 200.1.1.0 0.0.0.255
access-list 1 permit any
int eth 0
ip access-group 1 in
Apply Extended IP access list to int eth 0:
access-list 100 deny tcp host 1.1.1.1 host 2.2.2.2 eq 23
access-list 100 deny tcp 3.3.3.0 0.0.0.255 any eq 80
int eth 0
ip access-group 100 out
Apply Standard IPX access list to int eth 0:
access-list 800 deny 7a 8000
access-list 800 permit -1
int eth 0
ipx access-group 800 out
Apply Standard IPX access list to int eth 0:
access-list 900 deny sap any 3378 -1
access-list 900 permit sap any all -1
int eth 0
ipx access-group 900 out
Configuring the Router
Configuring the Router
You will be able to learn the basic commands for configuring a router.
sh running-config - details the running configuration file (RAM)
sh startup-config - displays the configuration stored in NVRAM
setup - Will start the the automatic setup; the same as when you first boot the router
config t - use to execute configuration commands from the terminal
config mem - executes configuration commands stored in NVRAM; copies startup-config to running-config
config net - used to retrieve configuration info from a TFTP server
copy running-config startup-config - copies saved config in running config (RAM) to NVRAM or "write memory" for IOS under ver.11
copy startup-config running-config - copies from non-volatile (NVRAM) to current running config (RAM)
boot system flash
boot system tftp - tells router which IOS file on the tftp server to boot from
boot system rom - tell router to boot from ROM at next boot
copy flash tftp - Copies flash to tftp server
copy tftp flash - Restores flash from tftp server
copy run tftp - Copies the current running-config to tftp server
copy tftp run - Restores the running-config from tftp server
General Commands
Here is a list of the general commands. These are the basic level commands and most commonly used
no shutdown - (enables the interface)
reload - restarts the router
sh ver - Cisco IOS version, uptime of router, how the router started, where system was loaded from, the interfaces the POST found, and the configuration register
sh clock - shows date and time on router
sh history - shows the history of your commands
sh debug - shows all debugging that is currently enabled
no debug all - turns off all debugging
sh users - shows users connected to router
sh protocols - shows which protocols are configured
banner motd # Your customized message here # - Set/change banner
hostname
clear counters - clear interface counters
Privileged Mode commands of a router
Learn how to work in the privileged mode of a router.
enable - get to privileged mode
disable - get to user mode
enable password
enable secret
Setting Passwords on router
Here you will be able to learn how to set the password on a router.
enable secret
enable password
Setting the password for console access:
(config)#line console 0
(config-line)#login
(config-line)#password
Set password for virtual terminal (telnet) access (password must be set to access router through telnet):
(config)#line vty 0 4
(config-line)#login
(config-line)#password
Set password for auxiliary (modem) access:
(config)#line aux 0
(config-line)#login
(config-line)#password
Router Processes & Statistics
By these command you can see the statistics and different processes of the router.
sh processes - shows active processes running on router
sh process cpu - shows cpu statistics
sh mem - shows memory statistics
sh flash - describes the flash memory and displays the size of files and the amount of free flash memory
sh buffers - displays statistics for router buffer pools; shows the size of the Small, Middle, Big, Very Big, Large and Huge Buffers
sh stacks - shows reason for last reboot, monitors the stack use of processes and interrupts routines
IP Commands
Here is a list of the IP Commands
Configure IP on an interface:
int serial 0
ip address 157.89.1.3 255.255.0.0
int eth 0
ip address 2008.1.1.4 255.255.255.0
Other IP Commands:
sh ip route - view ip routing table
ip route
ip route 0.0.0.0 0.0.0.0
ip classless - use with static routing to allow packets destined for unrecognized subnets to use the best possible route
sh arp - view arp cache; shows MAC address of connected routers
ip address 2.2.2.2 255.255.255.0 secondary - configure a 2nd ip address on an interface
sh ip protocol
CDP Commands (Cisco Discovery Protocol uses layer 2 multicast over a SNAP-capable link to send data):
sh cdp neighbor - shows directly connected neighbors
sh cdp int - shows which interfaces are running CDP
sh cdp int eth 0/0 - show CDP info for specific interface
sh cdp entry
cdp timer 120 - change how often CDP info is sent (default cdp timer is 60)
cp holdtime 240 - how long to wait before removing a CDP neighbor (default CDP holdtime is 180)
sh cdp run - shows if CDP turned on
no cdp run - turns off CDP for entire router (global config)
no cdp enable - turns off CDP on specific interface
IPX Commands
Enable IPX on router:
ipx routing
Configure IPX + IPX-RIP on an int:
int ser 0
ipx network 4A
Other Commands:
sh ipx route - shows IPX routing table
sh ipx int e0 - shows ipx address on int
sh ipx servers - shows SAP table
sh ipx traffic - view traffic statistics
debug ipx routing activity - debugs IPS RIP packets
debug ipx sap - debugs SAP packets
Ethernet
In this section you will learn about the lan terminology, basic ethernet networking overview, a general introduction to LAN, introduction to IEEE, lan topologies, wan standards. You can also find these categories in this site such as network tutorials, computer networking guide, what is networking, tech study guides, topologies, what is data recovery, wireless communication, computer interview questions and network certification. The IEEE standards have been developed by the International Standards Organization (ISO). The Institute of Electrical and Electronic Engineers (IEEE) in 1985 produced a series of standards for the Local Area Networks, which are called IEEE 802 standards.
These standards have been accepted widely throughout the IT world. One of the IEEE 802 standards, the IEEE 802.3 is known as “Ethernet”. Ethernet is the most widely used LAN technology. Ethernet was developed by Xerox corporations in 1972 and it was the first LAN.
According to the ISO standards allows manufactures to produce the devices and equipments, which are guaranteed to operate anywhere.
The Ethernet in its simplest form uses a passive bus that operates at 10 Mbps. The bus is formed from the co-axial cable, which connects all the PCs in the LAN.
A single LAN may have 1024 attached computers, although in the real practice most LANS have fewer computers than this number. One or more segments of the co-axial cable are attached to end to end to create the Ethernet Cable Segment. Each segment is terminated by 50 ohm resistors.
In today’s IT world the reliable and timely access to the information has become vital. Today coworkers thousands of miles apart from each other can share data, voice, video etc with the fractions of seconds. Similarly a larger number of the coworkers can review the research data simultaneously. The Internet allows businesses to share information and resources with their customers.
Ethernet is a communication protocol that is embedded in software and hardware devices that intended. Ethernet has become the standard computer networking protocol with the help of the Xerox, Intel and Digital
A basic LAN consists of the following components.
• Two or more computers.
• Network Interface card or LAN Card in each PC.
• Ethernet cable (Cat5, UTP/SPT) cable to connect the two computers.
• A hub, switch or router to route or direct the network traffic.
• Software for the communication/computer networking.
A network interface card (NIC) is attached and installed in each PC and is assigned a unique address. An Ethernet cable is used to connect two computers; Ethernet cable has RJ45connectors at both ends. There can be two scenarios 1. Two computers can directly connect with each other or 2. Each computer is directly connected with the hub/switch and hence communication occurs in the network. The hub or switch acts as relay.
Computer Network can be wireless. Despite of using Ethernet cable for the communication, Wireless Network Interface cards use radio waves to communicate with the wireless switch or hub. A small antenna is used in the wireless NICs, switches and hubs. Although the wireless networks are more easy to use as compared to the cabled networks, but more configurations and extra care is required to setup and run a wireless network.
The alternate technologies to Ethernet are “Token Ring”, which is used in the Ring Topologiesnetworks. Token Ring is designed by the IBM and ATM. In ATM networking, devices are connected with each other over a very large distance (thus forms the WAN), and behaves like LANs.
Ethernet is a well established and widely used network standard for small to medium sized Ethernet networks as well as for other networks. Ethernet has been used over the 3 decades and forms a very excellent networking/communication environment.
Ethernet Terms
Ethernet follows a simple set of rules. To understand these rules its important to understand the
following terminology.
• Node – The devices that are attached to the segments are nodes.
• Frame – The nodes (computers or network devices) communicates in the form of short messages that are known as frames. The frames are chunks of information with variable size.
• Segment – A single shared medium is known as a Ethernet segment.
• Medium – The Ethernet devices are attached to a common medium. The frames of the data travel along with that medium. This medium can be coaxial cable. Today most commonly used communication mediums are UTP/STP cable, fiber optic cables.
Frames are analogous in human language. We have some rules for constructed the sentences. The
Ethernet protocol specifies a set of rules for constructing the frames. The frames length varies. Each frame must contain source and destination address for the identification of the recipient and the send of the message. The nodes can be uniquely and easily identified. Each Ethernet devices must have a single unique address.
Compute networking standards has brought a revolution in the network computing and it made the communication very easy and standarized. Now every computer and networking devices has to to follow the same standard to communicate with each other.
Computer Network Topology
Here you will learn network topology introduction, how computers get connected, bus, star, hub, hybrid, mesh, tree topologies and network physical design. In Computer Networking “topology” refers to the layout or design of the connected devices. Network Topologies can be physical or logical. In this section I will illustrate on the different types of the topologies.
1.Computer network topologies can be categorized in the following categories.
• bus
• star
• ring
• mesh
• Tree.
Hybrid networks are the complex networks, which can be built of two or more above mentioned topologies.
Bus Topology:
Bus topology uses a common backbone to connect all the network devices in a network in a linear shape. A single cable functions as the shared communication medium for all the devices attached with this cable with an interface connector. The device, which wants to communicate send the broadcast message to all the devices attached with the shared cable but only the intended recipient actually accepts and process that message.
Ethernet bus topologies are easy to install and don’t require much cabling and only a main shared cable is used for network communication. 10Base-2 and 10BaseT are two popular types of the Ethernet cables used in the Bus topology. Also, Bus network works with very limited devices. Performance issues are likely to occur in the Bus topology if more than 12-15 computers are added in a Bus Network. Additionally, if the Backbone cable fails then all network becomes useless and no communication fails among all the computers. Unlike in the Star topology in which if one computer is detached from a network then there is not effect on the other computers in a network.
Ring Topology:
In ring Network, every computer or devices has two adjacent neighbors for communication. In a ring network, all the communication messages travel in the same directory whether clockwise or anti clockwise. Any damage of the cable of any cable or device can result in the breakdown of the whole network. Ring topology now has become almost obsolete.
FDDI, SONET or Token Ring Technology can be used to implement Ring Technology. Ring topologies can be found in office, school or small buildings.
Star Topology:
In the computer networking world the most commonly used topology in LAN is the star topology. Star topologies can be implemented in home, offices or even in a building. All the computers in the star topologies are connected to central devices like hub, switch or router. The functionality of all these devices is different. I have covered the detail of each networking devices in the separate portion of my website. Computers in a network are usually connected with the hub, switch or router with the Unshielded Twisted Pair (UTP) or Shielded Twisted Pair Cables.
As compared to the bus topology, a star network requires more devices & cables to complete anetwork. The failure of each node or cable in a star network, won’t take down the entire network
as compared to the Bus topology.
However if the central connecting devices such as hub, switch or router fails due to any reason,then ultimately all the network can come down or collapse.
Tree Topology:
Tree topologies are comprised of the multiple star topologies on a bus. Tree topologies integrate multiple star topologies together onto a bus. Only the hub devices can connect directly with the tree bus and each Hub functions as a root of a tree of the network devices. This bus/star/hybrid combination supports future expandability of the computer networks, much better than a bus or star.
Mesh Topology:
Mesh topology work on the concept of routes. In Mesh topology, message sent to the destination can take any possible shortest, easiest route to reach its destination. In the previous topologies star and bus, messages are usually broadcasted to every computer, especially in bus topology. Similarly in the Ring topology message can travel in only one direction i.e clockwise or anticlockwise. Internet employs the Mesh topology and the message finds its route for its destination. Router works in find the routes for the messages and in reaching them to their destinations.The topology in which every devices connects to every other device is called a full Mesh topology unlike in the partial mesh in which every device is indirectly connected to the other devices.
Summary:
Topologies are the important part of the network design theory. A better network can be built if you have the knowledge of these topologies and if you know the difference between each topology. Similarly you should have the knowledge of each network device so that you can properly use them according to your network needs. A misconfigured network can result in a waste of time and energy as well as a lots of troubleshooting methods to resolve the issue. So thebasic understanding of the network topologies and network devices is a must to build a good network.
Network Communication Devices
In this tutorial you will learn get the basic introduction to network devices such as nic adapters, routers, hubs, switches, modems, communication cables, lan/wan routers, gateway and other devices. A network is consists of a larger number of the communication devices. The simplest device that is used in the communication is the NIC adapter which is attached with the every computer in a network. If you want to build a LAN, you will need to have computers, hubs, switches, network adapters, UTP/STP cables, routers, internal/external modems, connectors, cable testers and clipping tool.
On the other hand if you need to build WAN, you will need to have routers, switches, dedicated or leased telephone lines such as ISDN lines, frame relay connection and other types of wan communication connections.
There are different communication mediums such as Ethernet cables, copper wire, coaxial cable, fiber optic cables, leased telephone lines and ever air is also a communication medium for the satellite communication. The most common networking medium is the LAN is the Ethernet cable (UTP/STP), which is used in the star topology. Hub is a central device of a network and every computer in a network is directly connected with the hub.
If the hub fails to work, the communication between the computers stops till the hub again starts working. Hub broadcasts the data to its every port, and then finding the destined computer, the data sent toward it. The switch is an advance form of the hub similar in functions but the advanced switches has a switching table in them. A advanced switch stores the MAC address of every attached computer and the data is only sent to the destined computer, unlike the hubs where data is sent to all ports. A router is a key device in the internet communication and wan communication system. A router has software called routing table and the source and destination addresses are stored in the routing table.
A router connects two logically and physically different networks. Router finds the IP address of the next hop (next router) and the data is sent toward it and so on. The well known routers developing companies are Cisco systems, Nortel, DLink and others. Every ISP, banks, corporate offices and multinational companies use routers for LAN and WAN communications and communication in their private networks. A gateway can be device or software in a network.
A gateway device connects the LAN with the internet. A gateway is directly exposed to the internet so it should be securely configured and in and out traffic should be monitored. If you are using DSL connection, you must need a DSL modem in your network. The telephone line is connected with the DSL modem and UTP/STP cable attaches your computer with the DSL modem. Modems are the devices that are used to modulate and demodulate the data. They convert analogue signals to digital and digital signals to analogue so that signals can travel on the telephone lines.
There are certain types of the cables that are used to connect two or more computers in a network. Fiber optic cable acts as a backbone between the ISPs and corporate offices. Data travels at the speed of light on the fiber optic cables. The cost and the installation cost of the fiber optic cable is very high but it is becoming very popular in the home networking and LANs also. In the local area networking, 10baseT/CAT5 cable is most commonly in use.
A server is a computer in network that provides services to the client computers such as logon requests processing, files access and storage, internet access, printing access and many other types of services. Servers are mostly equipped with extra hardware such as plenty of external memory (RAM), more data store capacity (hard disks), high processing speed and other features.
