Firewall is proved in harbor no 7 and Google find is also showed in harbor no 7 so ns am confused around how precisely ICMP usage the harbor number.

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Port numbers are a attribute of transfer layer protocols such together TCP and UDP. ICMP is really part of the internetworking layer (IP), so the attribute doesn"t exist at that layer.

And yes, I recognize that ICMP is encapsulated in IP, however it tho is considered component of the internetworking layer. That just shows the constraints of the model. To quote from RFC 792:

ICMP, offers the simple support of IP together if it to be a greater level protocol, however, ICMP is actually an integral part of IP, and also must be applied by every IP module. .

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answer Jun 5 "18 at 14:25

Ron TrunkRon trunk
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ICMP is IP protocol 1, TCP is 6 and UDP is 17. Therefore these space all various protocols with various behaviors.TCP and also UDP have actually Ports, ICMP go not.TCP and also UDP have an Echo company on harbor 7, sometimes called TCP-Ping/UDP-Ping, but they have actually nothing to perform with ICMP. Possibly this is her confusion.

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Banghua Zhao
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TCP and also UDP room transport protocols that usage port numbers to multiplex their usage between applications or processes.

This way, your browser using HTTP over TCP deserve to e.g. Affix multiple times to the exact same internet server. If the location port is the same (default for HTTP: 80), different resource ports are offered for each socket connection.

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In the exact same way, different applications deserve to use the same multiplexing, of course. On the server next there deserve to be different services on different TCP harbor - HTTP on 80, FTP ~ above 21, SMTP on 25, and so on. Or - making use of non-standard harbor - even different web servers on port 80 and also 8000, for instance.

Without ports, there could be only a solitary TCP link between any two hosts, or a single TCP service running on a server. (Likewise through UDP or any other transport protocol.)

ICMP is no a transfer protocol but a part that the IP protocol. The is supplied for signaling between hosts. Message that have the right to be sent include

Destination unreachable (a router signals the it"s can not to forward in the direction of the destination, a organize rejects a packet, or similar)Redirect message (a router wants the source to use an additional gateway)Time exceeded (a packet has exceeded the lifetime/hop count and also was dropped)Echo request / Echo reply (used byping)