S1 Chapters: 12, 13, 14

1
S1 Chapters 12, 13, 14

• C12 The Transport Layer
• C13 The Session Layer
• C14 - The Presentation Layer

2
Layer 5 The Session Layer

• Semester 1
• Chapter13

3
The Layer Functions
4
The Session Layer

• The session layer establishes, manages, and
  terminates sessions between applications. This
  includes starting, stopping, and resynchronizing
  two computers who are having a "rap session."

5
Email Session

• Problem You and a friend are emailing and wont
  take turns
• Solution 1 establish protocol/s that dictate
  rules for communicating with each other. This
  means that each of you agree to take turns and
  not interrupt. This is referred to as two-way
  alternate communication.
• Solution 2 each person would type whenever
  he/she wishes, regardless of who is transmitting,
  and you would assume that more info is always on
  the way. This is referred to as two-way
  simultaneous communication.

6
Dialogue Control

• dialogue control the decision at the session
  layer to use either two-way simultaneous
  conversation or two-way alternate communication.
• At this level, collisions can only occur as two
  messages pass each other, and cause confusion in
  either, or both, communicating hosts.

7
Dialogue Separation

• Dialogue separation - the orderly initiation,
  termination, and managing of communication.
• Checkpointing like AutoSave (separates part of
  the session)

8
Minor Separation Performed by Both Hosts

• back up the particular files
• save the network settings
• save the clock settings
• make note of the end point in the conversation

9
Layer 5 Protocols