1.4 - Multiuser Function and Transport Layer

1.4 - Multiuser Function and Transport Layer

1. Role of the Transport Layer

   • • Is responsible for logical communications between applications running on different hosts.
     • • The link between the application layer and the lower layers that are responsible for network transmission.
       • TCP vs UDP Header

2. Transport Layer Protocols

   • ▪ The transport layer includes the TCP and UDP protocols.
   • ▪ IP does not specify how the delivery or transportation of the packets takes place.
   • ▪ Transport layer protocols specify how to transfer messages between hosts, and are responsible for managing reliability requirements of a conversation.
   • TCP Header
     • TCP is a stateful protocol which means it keeps track of the state of the communication session.

3. Transmission Control Protocol

   • • Number and track data segments transmitted to a specific host from a specific application
   • Acknowledge received data
   • Retransmit any unacknowledged data after a certain amount of time
   • Sequence data that might arrive in wrong order
   • Send data at an efficient rate that is acceptable by the receiver

4. User Datagram Protocol (UDP)

   • UDP provides the basic functions for delivering datagrams between the appropriate applications, with very little overhead and data checking.
   • UDP Header
     • The UDP header is far simpler than the TCP header because it only has four fields and requires 8 bytes (i.e. 64 bits).

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