Transport Layer - TCP (Class 3)

Location of Transport Layer

Right after Application Layer

Transport Layer Functions

1) Link to Applications - Connect data to the correct app using port numbers.

2) Segment Data - Break data into pieces and reassemble it at the destination.

3) Manage Sessions - Help organize and maintain communication between devices.

1) Linking to Application layer

- TCP/UDP may serve multiple application layer protocols

- PORTS used to identify application(2-byte numbers)

2) Segmenting

Breaking up large files into smaller segments (and putting them back together)

3) Session Management

- Conversation between two computers or creating a virtual circuit

- Send data with a session is connection-oriented

- Send data w/o a session is connectionless Messaging

- TCP uses 3-way handshake

TCP Protocol Data Unit

Segment

What is the first step in the connection process?

3 way handshake

How is a message prepared for transmission in the connection process?

Message broken into segments

In what order are segments sent during the connection process?

Segments are sent in order

What happens to segments if a negative acknowledgement is received?

Segments are resent

What occurs at the end of the connection process?

Connection closed

Transport Layer Protocols

TCP, UDP

Transmission Control Protocol (TCP)

A protocol for sending packets that does error-checking to ensure all packets are received and properly ordered

User Data-gram Protocol (UDP)

A protocol for sending packets quickly with minimal error-checking and no resending of dropped packets

TCP example

HTTP

UDP example

Address request/DNS

TCP vs UDP

TCP creates connections and breaks down messages

UDP is connectionless, must fit into one segment