CS138-lecture-20210415

Network layer cont. #

Switching fabrics #

image_2021-04-15-09-05-05 image_2021-04-15-09-04-37 image_2021-04-15-09-05-40 image_2021-04-15-09-08-34 image_2021-04-15-09-09-29 image_2021-04-15-09-10-31

Since data can flow bidirectionally, inputs can become outputs, and vice versa.

Output ports #

image_2021-04-15-09-13-06 image_2021-04-15-09-15-36 image_2021-04-15-09-17-07

Input port queueing #

image_2021-04-15-09-19-25

IP: Internet Protocol #

image_2021-04-15-09-22-06 image_2021-04-15-09-24-00

ICMP = internet control message protocol

Datagram format #

image_2021-04-15-09-29-46

The header is 20 bytes long.

Upper layer can be TCP or UDP, or ICMP

A type could be multimedia, satellite signal etc, used for priority.

IP Fragmentation #

image_2021-04-15-09-31-31

MTU = max transfer size

image_2021-04-15-09-47-07

The original is 4000 bytes, but the MTU is 1500 bytes. So the original will be fragmented to accommodate the MTU.

image_2021-04-15-09-46-19 image_2021-04-15-09-52-48

Note: IP header is in every fragment, but the TCP header is only in the first. The TCP header is regarded as payload at the network layer.

image_2021-04-15-09-53-16

IPv4 #

image_2021-04-15-09-54-34

NIC = network interface card

A.B.C.D where each letter is 8 bits, so 32 bits total.

image_2021-04-15-09-57-21 image_2021-04-15-09-57-29

Subnets #

image_2021-04-15-09-57-44