Compiled by - Utpal Sharma, lecturer, Deptt of Computer Science

This page contains some notes and hyperlinks to notes on the topics - Session layer and Application layer according to the syllabus of the course CS 703 covered by me during Autumn 2001.

Session layer

A write-up on session layer collected from Worcester Polytechnic Institute has been placed here for quick access. This material is probably prepared as a summary of the chapter on Session Layer in Tanenbaum's Computer Networks, first edition.

The session service primitives can be divided into seven groups -
  1. Connection establishment.
  2. Connection release.
  3. Data transfer.
  4. Token management.
  5. Synchronisation.
  6. Activity management.
  7. Exception reporting.
The session service primitives are summarised in the following table :

OSI session primitive Req. Indic. Resp. Confirm. Meaning
S-CONNECT X X X X Establish a session
S-RELEASE X X X X Terminate a session gracefully
S-U-ABORT X X User-initiated abrupt release
S-P-ABORT X Provider-initiated abrupt release
S-DATA X X Normal data transfer
S-EXPEDITED-DATA X X Expedited data transfer
S-TYPED-DATA X X Out-of-band data transfer
S-CAPABILITY-DATA X X X X Control information data transfer
S-TOKEN-GIVE X X Give a token to the peer
S-TOKEN-PLEASE X X Request a token to the peer
S-CONTROL-GIVE X X Give all the tokens to the peer
S-SYNC-MAJOR X X X X Insert a major synchronisation point
S-SYNC-MINOR X X X X Insert a minor synchronisation point
S-RESYNCHONIZE-MAJOR X X X X Go back to a previous sync point
S-ACTIVITY-START X X Start an activity
S-ACTIVITY-END X X X X End an activity
S-ACTIVITY-DISCARD X X X X Abandon an activity
S-ACTIVITY-INTERRUPT X X X X Suspend an activity
S-ACTIVITY-RESUME X X Restart a suspended activity
S-U-EXCEPTION-REPORT X X Report of a user exception
S-P-EXCEPTION-REPORT X Report of a provider exception
(a) OSI Connection oriented session service primitives

S-UNITDATA X X Connectionless data transfer
(b) OSI Connectionless session service primitives