In not Of

Layer No.

Name

Description

Protocols*

Responsible party*

7 (highest)

Application

Everything at this layer is application-specific. This layer provides application services for file transfers, e-mail, and other network software services (authentication and privacy/security). Telnet and FTP are applications that exist entirely in the application level.

DNS, FTP, HTTP, SMTP,

Software applications (small utilities to major application suites)

6

Presentation

The presentation layer works to transform data into the form that the application layer can accept. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer.

HTML

GIF

TIFF

JPEG

ASCII

Client Operating System (Windows 2000, XP, Linux, BeOS, etc)

5

Session

This layer establishes, manages and terminates connections between applications. The session layer sets up, coordinates, and terminates conversations, exchanges, and dialogues between the applications at each end. It deals with session and connection coordination.

NetBIOS, Named Pipes, RPC

Network Operating System (Netware, Windows 2003, etc)

4

Transport

This layer provides transparent transfer of data between end systems, or hosts, and is responsible for end-to-end error recovery and flow control. It ensures complete data transfer.

TCP, UDP,  NetBEUI

3

Network

This layer is responsible for translating computername to MAC address. Routing and forwarding are functions of this layer, as well as addressing, internetworking, error handling, congestion control and packet sequencing.

IP, ICMP, IPX,

2

Data link

At this layer, data packets are encoded and decoded into bits. It furnishes transmission protocol knowledge and management and handles errors in the physical layer, flow control and frame synchronization. The data link layer is divided into two sublayers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking

IEEE 802.2

IEEE 802.3

802.5 (Token Ring)

HDLC

Frame Relay

FDDI

ATM

PPP

ARP

Network (Routers, switches, gateways, hubs, etc)

1 (lowest)

Physical

This layer conveys the bit stream - electrical impulse, light or radio signal -- through the network at the electrical and mechanical level. It provides the hardware means of sending and receiving data on a carrier, including defining cables, cards and physical aspects. Fast Ethernet, RS232, and ATM are protocols with physical layer components.

ISDN

V.24

V.35

FDDI

802.3

802.5

Ethernet

RJ45

10 Base-T 100 Base-T