CSC Networking Scott Heggen

Agenda Finish TCP – Part 1

Let’s Review What does the network layer do? What does the data link layer do? What does the physical layer do?

Data

Data.html

HTTP

HTTP, Data

TCP, Source:80, Destination:1030

IP, Source: , Destination: TCP, HTTP, Data

Ethernet, Source: , Destination: IP, TCP, HTTP, Data FCS

Data

Ethernet, Source: , Destination:

Data

Ethernet, Source: , Destination:

Data IP, Source: , Destination: R1(config)# ip route

Data Ethernet, Source: Destination:

Data

Ethernet, Source: Destination:

Data IP, Source: , Destination:

Data Ethernet, Source: Destination:

Data

Ethernet, Source: Destination:

Data IP, Source: , Destination:

Data Ethernet, Source: Destination:

Data

Ethernet, Source: , Destination:

Data

Ethernet, Source: , Destination: IP, TCP, HTTP, Data FCS

IP, Source: , Destination: TCP, HTTP, Data

HTTP, Data TCP, Source:80, Destination:1030

HTTP, Data

Data.htmlHTTP

Data.html

Data

Reflecting on this process so far… Do any of the bottom three layers handle error correction? Do any of the bottom three layers handle in-order delivery? Do any of the bottom three layers handle delivery of data to the correct device? Do any of the bottom three layers handle delivery of data to the correct process within the device? Do any of the bottom three layers handle controlling the flow of data (slowing down/speeding up data transfer rate??) Do any of the bottom three layers handle breaking up data into smaller segments?

Transport Layer The transport layer does all of those things (except delivery of data to the correct device; that was network layer (remember routing?!!?)) Flow control (using windowing) In-order delivery (reassembling segments into the correct order) Error recovery (lower layers handled error detection only; transport actually fixes it!) Segmentation (other layers do break the message into smaller chunks, but transport layer does it better) Identifies applications within a device via port numbers