---
# System prepended metadata

title: 4/21 Network Protocols

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# 4/21 Network Protocols

## Spanning Tree Algorithm

Max/Min

find shortest path for 

![](https://i.imgur.com/NI1iZ1K.png)

## Virtual Circuit Services – Multi-Protocol Label Switching (MPLS)


## Routing vs. Forwarding

![](https://i.imgur.com/X8liE8c.png)

Routing: use algorith,like Dijkstra, 

Routing refers to the network-wide algorithm,like Dijkstra, that determines end-to-end paths that packets take from source to destination.

Forwarding refers to the router-local action of transferring the packet from an input link interface to the output link interface.



## DHCP

Getting IP Addresses for Host Network Interfaces

## ARP (Address Resolution Protocol) packet

work in LAN,

ARP send a broadcast message to ask the subject question for every host and host reply to the sender’s MAC address

can cache the IP address

:::info
Who has ip ......?
:::
![](https://i.imgur.com/r1KLRaM.png)

走過會建立在ARP table中，下次可以從中查詢要走哪一個interface即可

## Path MTU Discovery （最佳化package size）
![](https://i.imgur.com/OnYYpAi.png)

## IPv4 Fragmentation

packet太大，需要切碎，依照MTU切

## Path MTU Discovery

![](https://i.imgur.com/ofEF0gG.png)


## ICMP message

:::info
ping ...
traceroute ...
:::

![](https://i.imgur.com/xEYldcq.png)
![](https://i.imgur.com/v30BjfF.png)

更正：`Time exec...`>>`TTL`

## Tracerouth
![](https://i.imgur.com/vS8lfZ8.png)


## IPv6 transver
![](https://i.imgur.com/MdBfbPr.png)

# Routing

## shortest path 
![](https://i.imgur.com/TpUxEeC.png)

## shortest path protocal
![](https://i.imgur.com/VMNawSy.png)