This document summarizes the functions of the seven layers of the OSI model. It describes the key responsibilities of each layer, including physical addressing and transmission at the physical layer, framing and error control at the data link layer, routing at the network layer, connection control and flow control at the transport layer, synchronization at the session layer, translation and encryption at the presentation layer, and various application-specific functions at the application layer such as file transfer, email, and directories. Examples of common protocols are provided for some layers.

1. FUNCTIONS OF OSI
LAYERS
T S Pradeep Kumar
VIT Chennai
http://www.pradeepkumar.org

2. PHYSICAL LAYER
Representation of bits
Data Rate
Synchronization of bits
line configuration
physical topology
Transmission mode
Eg: IEEE802.1x, PON, OTN,
DSL, USB, Bluetooth, etc

3. DATA LINK LAYER
Framing
physical addressing
flow control
error control
access control
Eg: LLC, Frame relay, PPP,
ATM,

4. NETWORK LAYER
logical addressing
routing
Eg: IPv4, IPv6, ICMP,
IGMP, IPX, AppleTalk

5. TRANSPORT LAYER
Service point addressing
segmentation and
reassembly
connection control
flow control
error control
TCP, UDP, SCTP, DCCP

6. SESSION LAYER
dialog control
synchronization
Named Pipe, NetBIOS,
RTP, SOCKS

7. PRESENTATION LAYER
translation
encryption
compression
MIME, XDR

8. APPLICATION LAYER
network virtual terminal
file transfer, access and
management
email services
directory services
NFS, SMTP, SNMP,
Telnet, DHCP, HTTP, FTP

9. Questions????