TCP/IP

TCP/IP

Protocol is a set of rules that determines how the data is transmitted over the network. It is a communication standard followed by hosts in a network to communicate with each other. Protocols regulate the type of network access method, compression techniques while transferring data, the topologies, the cabling methods and even the speeds of data transfer.

The Internet protocol suite is the networking model and a set of communications protocols used for the Internet and similar networks. It is commonly known as TCP/IP, because its most important protocols, the Transmission Control Protocol (TCP) and the Internet Protocol (IP) were the first networking protocols defined in this standard. It is occasionally known as the DoD model due to the foundational influence of the ARPANET in the 1970s (operated by DARPA, an agency of the United States Department of Defense).

TCP/IP

TCP/IP (Transmission Control Protocol/Internet Protocol) is the basic communication protocol used by internet. It is also used for communication in private network such as Intranet. The TCP/IP is a two layer protocol.

The higher layer TCP protocol divides the message into smaller packets called segments and transmits those segments over the network. These packets are then received by the TCP layer of the other machine. This layer reassembles the segments into the original message. TCP performs its functions the same way regardless of whether two computers are on the same network or on different network separated by Internet.

The lower layer IP protocol manages the addressing part of the packets so that they will reach the correct destination. Each router used in the network checks these addresses to determine where to forward the packets. Even if the packets of same message follow different routes to reach the destination, they will be assembled into original message at the destination.

TCP/IP Protocol Suit:

The TCP/IP protocol suit, also referred to as the internet protocol suite, is the set of communications protocols that implements the protocol stack on which the internet and most commercial networks run. It is named after the two most important protocols in the suite i.e. Transmission Control Protocol (TCP) and the Internet Protocol (IP).

The TCP/IP protocol suit-like the OSI reference model-is defined as a set of layers. Upper layers are logically closer to the user and deal with more abstract data, relying on lower layer protocols to translate data into forms that are transmitted physically over the network. Prior to the OSI model, the TCP/IP protocol suite was developed and hence the layers in the TCP/IP protocol suite differ from the layers of the OSI model.

Four layers of TCP/IP protocol suite are:

Ø  Network Access

Ø  Internet

Ø  Transport

Ø  Application

                                  OSI                                     TCP/IP

Application		Application
Presentation
Session
Transport		Transport
Network		Internet
Data link		Network  Access
Physical

Network Access layer:

The lowest layer of the TTCP/IP protocol stack is the network access layer. The network access layer contains two sublayers, the media access control (MAC) sublayer and the physical sublayer. The MAC sublayer aligns closely with the data link layer of the OSI model, and is sometimes referred to by that name. The physical sublayer aligns with the physical layer of the OSI model.

Internet Layer:

The internet layer of the TCP/IP model maps to the network layer of the OSI model. Consequently, the Internet layer is sometimes referred to as the network layer.TCP/IP supports the Internetworking Protocol (IP) at the Internet layer. IP uses four supporting protocols that are ARP, RARP, ICMP and IGMP

Internet Protocol (IP):

IP is a transmission mechanism used by the TCP/IP protocol. IP is a connectionless and unreliable datagram protocol and provides no error checking. IP transfers data in the form of packets called datagrams. Datagrams can travel through various routes to reach the destination and may not arrive in the order in which they were sent. IP does not recorder the data once they reach the destination. Also, IP does not recorder the data once they reach the destination. Also, IP does not keep a track of the routes of the datagram.

Address Resolution Protocol (ARP)

ARP is used to determine the physical address (MAC address) of the device only when its IP address is known. ARP is also used to translate the IP address to Ethernet MAC Addresses. Each device has a physical address embedded on the network Interface Card (NIC). ARP is used to associate with the physical address.

Reverse Address Resolution Protocol (RARP)

RARP is used to determine the IP address of the host only when the physical address (MAC Address) is known. It is useful when the computer is connected to the network for the first time.

Internet Control Message Protocol (ICMP)

This protocol is used by computer and gateways to send notification of datagram problems such as query and error reporting messages back to the sending device. Its only function is to report problems to the original sender not to correct them. Ping command is an example of ICMP protocol.

Internet Group Message Protocol (IGMP)

This protocol is used for multicasting means to transmit message to multiple recipients at the same time. Class D IP address is used for this protocol.

Transport Layer:

At the transport layer, the TCP/IP defines the TCP and UDP protocols. These two protocols are responsible for delivering messages from a running process to other process, whereas IUP delivers the packet from one physical device to another.

User Datagram Protocol (UDP)

It is a connection less/stateless and unreliable transport protocol. It adds port addresses and error control information to the data and delivers the data. It is fast as compared to TCP.

Transmission Control Protocol (TCP)

It is a connection-oriented and reliable transport protocol. It divides data into segments each having a sequence number. These sequence numbers are useful at the receiving end to rearrange the segments into original order.TCP transmits data in a single stream and ensures that data will be transmitted in a sequence at the receiver.

Stream control Transmission Protocol (SCTP)

It is reliable and connection-oriented transport protocol that offers acknowledged, error-free and non-duplicated transmission of multiple streams of data. Unlike TCP, SCTP make sure that multiple streams of data will be transmitted simultaneously. SCTP can be used to manage connection over wireless network and transmission of multimedia data. It supports new applications such as voice over the internet. It combines the best features of UDP and TCP.

Responsibilities of transport layer are:

Service-point Addressing-

they may be number of programs running at the same time on a computer.for this purpose, source-to-destination delivery should also include process-to-process delivery. Data must be transfered from a specific proccess (running program) on one computer to a specific process on another comp[uter and to accomplish this, port address is required.Thus, transpppport layer includes service-point address (also referred to as port address) in the header. Using these port addresses transport layer delivers the packets to the correct process.

Segmentation and reassembly-

A message is devided into segments with each segment having a sequence number. When the message arrives at the destination, withn the help of these sequence numbers, the transport layer ressembles the message correctly.sequence numbers also enable transport lasyer to determine and replace the segments that were lost in the transmission.

Connection Control-

Transport layer provides either connection-oriented or connectionless service. In connection-oriented service, transport layer establishes a connection with the transport layer at the destination before transmitting segments and terminates the connection when all the data is transferred. In connectionsless sevice, transport layer treats each  segment as individual packet and transmits it to the transport layer at detination.

Error Control-

Transport layer also performs error checking. Error control takes place end to end. Transport layer at the sending machine ensures that the entire message is dedlivered at the receviing machine without an error. Segments are retransmitted to achieve error correction.

Application Layer

The application layer of the TCP/IP model corresponds to the application layer of the OSI reference model. Many protocols such as SMTP, DNS, SNMP, NFS, and TFTP are defined at this layer.

Simple mail Transfer Protocol (SMTP)

It is a protocol used to transfer e-mail messages across the network and the Internet. It helps in sending messages such as text or message with an attachment to single or multiple recipients.

File Transfer Protocol (FTP)

It is used to exchange files from one host to another connected over the Internet. Server and client are involved in the process of transferring file.

Domain Name System (DNS)

It is used to store and resolve the internet domain names of hosts to IP addresses.

Simple Network Management Protocol (SNMP)

It is used to manage and control devices, performance and security of the network. It is based on the client-server model.

Network File System (NFS)

Allows computers on different operating system e.g. Windows and UNIX to share files and disk storage.

Trivial file Transfer Protocol (TFTP)

Uses UDP to upload or download files it is a simple form of FTP and does not provide security features.

Port Numbers

A port numbers is a way to identify a specific process to which an Internet or other network message is to be forwarded when it arrives at a server. The well known ports are assigned by IANA (Internet Assigned Numbers Authority).

Port	Protocol
20	FTP, File Transfer Protocol, data
21	FTP, File Transfer Protocol, control
23	Telnet, Terminal Network
25	SMTP, Simple File Transfer Protocol
53	DNS
67	IPV4 client
68	IPV4 server
80	HTTP, Hypertext Transfer Protocol
110	POP, Post Office Protocol, version 3.
143	IMAP, Interactive Mail Access Protocol
443	HTTPS.HTTP over SSl/TLS
464	Kerberos change/set password
546	IPV6 client
547	IPV6 server

TCP/IP Configuration

There are some basic TCP/IP configuration parameters. The users should be familiar with TCP/IP parameters like host name, DHCP client, IP address, domain name, broadcast address, default gateway before configuring TCP/IP and connecting to Internet.

Host name

Individual computer names are called as host names in a network. Some applications such as e-mail, uses host name to identify the destination to which the packet has to be sent. The host name for a system is unique on a network.

Domain name

A Domain is not a single computer, but a holding space into which computer names can be added. Individual computer names in the DNS (Domain Name System) naming convention are commonly called as host names.

IP address

 No two systems on the same network share the same IP address; if two machines accidently receive the same address, “IP address conflict” error will occur. These IP addresses need to be configured in the machines.

DHCP Client

Dynamic Host Configuration Protocol (DHCP) is a TCP/IP service protocol. DHCP offers dynamic leased configuration of host IP addresses and allots other configuration parameters to network clients. DHCP provides secure, reliable TCP/IP network configuration, prevents address conflicts, and helps conserve the use of client IP addresses on the network.

DHCP uses a client/server model where the DHCP server maintains centralized management of IP addresses that are used on the network. DHCP-supporting clients can then request and obtain lease of an IP address from a DHCP server.

DHCP enables individual client machines on a network to configure all of their IP settings automatically. The DHCP server stores all of the necessary IP information for the network, and provides that information to clients as they boot into the network.

Default router

A default router is the default gateway used by the host to access hosts on other networks. In a TCP/IP network, the nearest router to a particular host known as default router. This router’s IP address is a part of necessary TCP/IP configuration used for communicating with another network as well. If a system wants to send data to a system on another network, a local network must connect via a router. The router connecting a local network must be aware of the method to address packets for other systems that are not part of its local network. This router is called as default gateway, gateway router.

DNS Server

The Domain Name System (DNS) is used to manage the names of Web sites and other Internet domains. DNS allows you to type names into your web browser like www.jetkinginfotrain.com and your computer to automatically find that address on the Internet. A key element of the DNS is a worldwide collection of DNS servers.

Broadcast address

An IP address which enables the information to be broadcasted to all computers on a subnet rather than only to a specific computer is known as a broadcast address. A broadcast is a packet addressed to all machines. In TCP/IP, the general broadcast address is 255.255.255.255.In data link layer address FF-FF-FF-FF-FF-FF a NIC attaches to a frame when it sends a broadcast to every other NIC on the network.