TCP/IP Suite and Its Member Protocols

Any communication requires two parties (active-listening and speaking). Communication between devices is done in machine language. Different types of devices manufactured by various companies need to communicate using a common language which is known as a protocol.

Any introduction to internet protocols should explain the various other protocols that are a part of TCP/IP suite. A protocol is basically a set of rules and conventions that need to be followed to establish connection and transfer of data between two devices. There are various protocols and networks often support multiple protocols. The mostly used protocol that is found on the internet and in home networks is TCP/IP - Transmission Control Protocol/Internet Protocol. TCP/IP consist of many other associated network protocols and owes its existence to ISO/OSI which now serves as a reference to all other protocols.

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TCP/IP Suite

The layer structure is built in a manner such that each layer treats all of the information it receives from the upper layer as data and adds control information (header) in the front of that data and passes it on to the lower layer. When data is received the opposite process takes place. Functions of the layers are

Application Layer (Layer 5)

This provides functions for user application to communicate over the network and is highly specific to the application being performed. This layer includes all applications protocols that use host-to-host transport. It manages sessions ('socket' and 'port' is used by TCP/IP for sessions) between cooperating applications. Other functions are data encryption, decryption, compression and decompression. There are many protocols implemented in the application layer they are

BGP-Border Gateway Protocol Version4
COPS - Common Open Policy Service
DNS - Domain Name Service
FANP - Flow Attribute Notification Protocol
Finger - User Information Protocol
FTP - File Transfer Protocol
HTTP - Hypertext Transfer Protocol
IMAP4 - Internet Message Access Protocol, rev 4
IMPPpre/IMPPmes - Instant Messaging and Presence Protocols
IPDC - IP Device Control
IRC - Internet Relay Chat Protocol
ISAKMP - Internet Message Access Protocol (version 4rev1)
NTP - Network Terminal Protocol
POP3 - Post Office Protocol version 3
Radius - Remote Authentication Dial In User Service
RLOGIN - Remote Login
RTSP - Real-time Streaming Protocol
SCTP-Stream Control Transmission Protocol
S-HTTP - Secure Hypertext Transfer Protocol
SLP - Service Location Protocol
SMTP - Simple Mail Transfer Protocol
SNMP- Simple Network Management Protocol
SOCKS - Socket Secure (Server)
TACACS+ - Terminal Access Controller Access Control System
TELNET - TCP/IP Terminal Emulation Protocol
TFTP - Trivial File Transfer Protocol
WCCP - Web Cache Coordination Protocol
X-Window - X Window

Transport Layer (Layer 4)

Whatever be the application, data needs to be exchanged reliably and must not be dependent on the application. TCP ensures host-to-host reliable information exchange where as UDP-User Datagram Protocol does not have end-to-end reliability checking.
Protocols used are

Mobile IP - Mobile IP Protocol
RUDP - Reliable UDP
TALI - Transport Adapter Layer Interface
TCP - Transmission Control Protocol
UDP - User Datagram Protocol
Van Jacobson - compressed TCP
XOT - X.25 over TCP

Network Layer (Layer 3)

This is also spoken of as the internet layer and is the primary protocol of IP over the internet. This provides routing function across multiple networks and is implemented not only in end systems but also in routers on the network to help in traversal of data. The protocols they support are

DHCP - Dynamic Host Configuration Protocol
DVMRP - Distance Vector Multicast Routing Protocol
ICMP/ICMPv6 - Internet Control Message Protocol
IGMP - Internet Group Management Protocol
IP - Internet Protocol version 4
IPSec - Internet Protocol Security
IPv6 - Internet Protocol version 6
MARS - Multicast Address Resolution Server
PIM - Protocol Independent Multicast-Sparse Mode (PIM-SM)
RIP2 - Routing Information Protocol
RIPng for IPv6 - Routing Information Protocol for IPv6
RSVP - Resource ReSerVation setup Protocol
VRRP - Virtual Router Redundancy Protocol

Data Link Layer (Layer 2)

It is also known as the network layer. Its concern is the link between the data transmission device and the network. Network address of the destination should be added so that the data can go to the appropriate destination. Standards vary for circuit-switching, packet-switching (frame, relay) local area networks (Ethernet) and others

ARP - Address Resolution Protocol
ARCnet
CDP - Cisco Discovery Protocol
DCAP - Data Link Switching Client Access Protocol
Econet
Ethernet
FDDI - Fiber Distributed Data Interface
Frame Relay
HDLC - High Level Data Link Control
LocalTalk
L2F - Layer 2 Forwarding Protocol
L2TP - Layer 2 Tunneling Protocol
PPP - Point-to-Point Protocol
XPPTP - Point-to-Point Tunneling Protocol
SLIP - Serial Line Internet Protocol (obsolete)
StarLan
Token ring

Physical Layer (Layer 1)

The physical layer defines the physical interface between the data transmission device (computer) and the transmission medium. Characteristics of the transmission medium, nature of the signals, the data rate and related specifications are a part of the physical layer.

TCP/IP is actually a suite of protocols and the major ones are

Address Resolution Protocol (ARP)
Domain Name System (DNS)
File Transfer Protocol (FTP)
Hypertext Transfer Protocol (HTTP)
Interactive Mail Access Protocol (IMAP)
Internet Control Message Protocol (ICMP)
Internet Protocol (IP)
Open Shortest Path First (OSPF)
Post Office Protocol (POP3)
Routing Information Protocol (RIP)
Simple Mail Transport Protocol (SMTP)
Transmission Control Protocol (TCP)
User Datagram Protocol (UDP)

The IP Packet format is given below

32bits

Version

IHL

Type of service

Total length

Identification

Flags

Fragment offset

Time to live

Protocol

Header checksum

Source IP Address

Destination IP Address

Option + Padding

Data

Intranets and Extranets

Private Networks share part of an organization's information or operation with its employees. The means or medium used can be dedicated lines to transfer data, PSTN for phone service, ISDN for voice and video conferencing or a visible service which is usually a Website. Internet and Client-Servers use the same protocols of TCP/IP Protocol suite. Thus the connection of these private networks via the internet results in an Intranet.

Firewalls, gateways, authentication, encryption and the use of VPN technologies make security and performance on public services better.

Intranets are commonly owned by communications, HR or CIO area of large organizations to deliver tools and applications such as sophisticated directories, sales and CRM tools, project management etc. Intranets cannot be accessed by the general public.

Extranet is an extension of the intranet over the World Wide Web such that limited access of the intranet is provided to the public. The access can be for customers, partners, suppliers or others outside the company. The part that access has been granted to becomes the extranet. This can provide access to research inventories and internal databases. Some portions may be free, others portions of information may require a payment. What is needed is privacy of information both to the company and of the purchaser. Firewalls, server management, authentication, encryption, digital certificates and the use of VPN ensure confidentiality and security.

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