2023-11-16

Introduction

Summary

keywords

TODO

HW

Exercise*

Next time

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IPv6

• out of 40 bytes header, 32 bytes are used for source IP, destination IP.

• Fragmentation header fields are omitted.

• How do they handle big MTU fragmentation? The router sends back a request of a smaller MTU. fragmentation is done in the end user device.

• option fields are omitted. The header size is now fixed.

How was IPv6 transition done?

Tunnelling

• IPv6 datagram carried as payload in IPv4 datagram among IPv4 routers

• used extensively in 4G/5G

source and destination IP of IPv4 headers will be the IPv6-supporting routers. ![[Pasted image 20231116131611.png]]

Generalized Forwarding, SDN

• forwarding table for generalized forwarding is called flow table

• flow tables are defined by controllers.

• Match plus action

  • many header fields are accessed and used.

  • many action possible : drop/copy/modify/log packet

Flow table abstraction

• flow : defined by header field values : mac(link), IP (network), port(transport) ![[Pasted image 20231116133736.png]]

• generalized forwarding

  • match

  • actions

  • priority

  • counters

OpenFlow

protocol of exchanging these flow table infos.

1. Implement what destination-based forwarding did:

2. example ) firewall functionality

3. example) layer2 destination-based forwading

Match-action

1. Router functionality

2. Switch functionality

3. Firewall functionality

4. NAT functionality

Middlebox

Any intermediate devices that gives extra functionality to the network. It alleviates the thin waist problem of the Internet.