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how will this work (pic attached)

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07-02-2012, 11:29 AM

Fuzz

Cisco Veteran

Join Date: Nov 2008

Location: Birmingham, UK

Posts: 1,237

ICMP is IP protocol number 1, TCP is IP protocol number 6, UDP is IP protocol number 17.

ICMP relies on IP to route the packet to the correct host, so it is not a layer 3 protocol. Where you would have a port field in the TCP or UDP header, you have a type filed in the ICMP header. It amounts to the same thing, just a different name.

http://tools.ietf.org/html/rfc792

Quote:

ICMP uses the basic support of IP as if it were a higher level protocol

& http://en.wikipedia.org/wiki/Internet_Control_Message_Protocol

Quote:

The ICMP header starts after the IPv4 header

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Last edited by Fuzz; 07-02-2012 at 11:38 AM.

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