Friday, March 11, 2011

Describe about TCP/IP Layers and Protocols

The TCP/IP model defines four categories of functions that must occur for communications to be successful. Most protocol models describe a vendor-specific protocol stack. However, because the TCP/IP model is an open standard, one company does not control the definition of the model.

TCP/IP Layer :
Application :
Represents data to the user and controls dialog. Example : DNS, Telnet, SMTP, POP3, IMAP, DHCP, HTTP, FTP, SNMP
Transport :
Supports communication between diverse devices across diverse networks. Example : TCP, UDP
Internet :
Determines the best path through the network. Example : IP, ARP, ICMP
Network access :
Controls the hardware devices and media that make up the network. Example : Ethernet, Frame Relay

In coming days, we will review these protocols in more detail. For now, a brief description of the main TCP/IP protocols follows:
■ Domain Name System (DNS): Provides the IP address of a website or domain name so a
host can connect to it.
■ Telnet: Allows administrators to log in to a host from a remote location.
■ Simple Mail Transfer Protocol (SMTP), Post Office Protocol (POP3), and Internet
Message Access Protocol (IMAP): Used to send email messages between clients and servers.
■ Dynamic Host Configuration Protocol (DHCP): Assigns IP addressing to requesting
■ Hypertext Transfer Protocol (HTTP): Used to transfer information between web clients and
web servers.
■ File Transfer Protocol (FTP): Allows the download and upload of files between an FTP
client and FTP server.
■ Simple Network Management Protocol (SNMP): Used by network management systems to
monitor devices attached to the network.
■ Transmission Control Protocol (TCP): Allows virtual connections between hosts on the
network to provide reliable delivery of data.
■ User Datagram Protocol (UDP): Allows faster, unreliable delivery of data that is either
lightweight or time-sensitive.
■ Internet Protocol (IP): Provides a unique global address to computers for communicating
over the network.
■ Address Resolution Protocol (ARP): Finds a host’s hardware address when only the IP
address is known.
■ Internet Control Message Protocol (ICMP): Used to send error and control messages
including reachability to another host and availability of services.
■ Ethernet: The most popular LAN standard for framing and preparing data for transmission
onto the media.
■ Frame Relay: Also a framing standard; one of the most cost-effective WAN technologies
used to connect LANs.

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