https://github.com/alinpahontu2912/simple-router

First Homework for Communication Protocols course
https://github.com/alinpahontu2912/simple-router

arp communication-protocol icmp ip router

Last synced: over 1 year ago
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First Homework for Communication Protocols course

• Host: GitHub
• URL: https://github.com/alinpahontu2912/simple-router
• Owner: alinpahontu2912
• Created: 2021-07-19T11:44:01.000Z (almost 5 years ago)
• Default Branch: main
• Last Pushed: 2021-07-19T11:44:50.000Z (almost 5 years ago)
• Last Synced: 2025-01-31T13:24:14.433Z (over 1 year ago)
• Topics: arp, communication-protocol, icmp, ip, router
• Language: C
• Homepage:
• Size: 9.77 KB
• Stars: 0
• Watchers: 1
• Forks: 0
• Open Issues: 0
• Metadata Files:
  • Readme: README

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README

          
Simple Router Implementation

	Implemented a simple router using the following communication protocols:

Ethernet, Ip, ICMP and ARP. 

	Ethernet protocol: gives information about the source and destination mac

adresses and specify the type of the protocol in the received packet.

	

	If the ethernet type is ARP:

		- if the ARP message is a request, a reply will be sent with the wanted

mac adress

		- if the ARP message is a reply, the arp table will be updated and the

remaining messages will be sent to the newly found destination

	If the ethernet type is IP:

		- if it also contains an ICMP header, is destinated to the router and

the message is of type ECHO REQUEST, an ECHO REPLY will be sent back

		- if the checksum is wrong, the packet will be dropped

		- if the packet is about to expire, an ICMP error message will be sent 

back to the source of the packet

	

	Forwarding process:

		- when a packet is received, the next hop will have to be determined 

from the route table entries:

			- if there is no good entry in the route table, an ICMP error of 

type DESTINATION UNREACHABLE will be sent back

		- I will then search for the destination MAC in the arp table:

			- if there is good entry, an ARP request will be sent, so that the

wanted MAC adress can be found (the message is a broadcast message, thus the 

destination MAC of this request wwill be ff:ff:ff:ff:ff:ff)

		- if both an arp entry and route tanle entry are found, the message is 

sent to the next destination.

Bonus: tried to implement the checksum modificiation using the incremental 

algorithm from RFC 1624 (Equation number 4). The 16-bit field value is formed

out of the ttl field (8 bits), which is followed by the protocol field(8 bits).