CSC 412 - NetworkingScott Heggen

Agenda

• Finish 4 + 1 • 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?

HTTP GET REQUEST

Web Application

Data0101010110001011010110100010110010110101

011010101100101

Web Application

Data.html

Web Application

Data.htmlHTTP

HTTP, Data

HTTP, DataTCP, Source:80, Destination:1030

IP, Source:8.1.1.1, Destination:130.4.3.3 TCP, HTTP, Data

Ethernet, Source:0010.1111.1111, Destination:0030.3333.3333 IP, TCP, HTTP, Data FCS

Dat

a

SW1

Data

SW1

DataEthernet, Source:0010.1111.1111, Destination:0030.3333.3333

MAC Address TablePort MAC 1 0010.1111.1111 9 0030.3333.3333

SW1

Data

Dat

a

R1

Data DataEthernet, Source:0010.1111.1111, Destination:0030.3333.3333

R1

DataIP, Source:8.1.1.1, Destination:130.4.3.3

R1(config)# ip route 130.4.0.0 255.255.0.0 200.55.99.251

IP Routing TableDest. Next-Hop130.4.0.0 200.55.99.251

. .

. .

R1

DataEthernet, Source:0030.3333.3334 Destination:0040.4444.4444

R1

Data

Data

R2

DataDataEthernet, Source:0030.3333.3334

Destination:0040.4444.4444

R2

DataIP, Source:8.1.1.1, Destination:130.4.3.3

IP Routing TableDest. Next-Hop130.4.0.0 100.55.99.251

. .

. .

R2

DataEthernet, Source:0040.4444.4445 Destination:0050.5555.5555

R2

Data

Data

R3

DataDataEthernet, Source:0040.4444.4445

Destination:0050.5555.5555

R3

DataIP, Source:8.1.1.1, Destination:130.4.3.3

R3

DataEthernet, Source:0050.5555.5556 Destination:0020.2222.2222

R3

Data

Data

SW2

Data

SW2

DataEthernet, Source:0050.5555.5556, Destination:0020.2222.2222

MAC Address TablePort MAC 1 0050.5555.5556 9 0020.2222.2222

SW1

Data

Dat

a

Data

Ethernet, Source:0050.5555.5556, Destination:0020.2222.2222 IP, TCP, HTTP, Data FCS

IP, Source:8.1.1.1, Destination:130.4.3.3 TCP, HTTP, Data

HTTP, DataTCP, Source:80, Destination:1030

HTTP, Data

Email Application

Web Application

FTP Application

Web Application

Data.htmlHTTP

Web Application

Data.html

Web Application

Data0101010110001011010110100010110010110101

011010101100101

Web Application

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