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ICMP ?
- Thread starter BigA1
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ICMP is not port specific, you can send an ICMP packet down any port number you choose. ICMP is a protocol much like TCP is, TCP will also operate on any port that is specified. david e
*end users are just like computers, some you can work with...others just need a simple reBOOTing to fix their problems.*
*end users are just like computers, some you can work with...others just need a simple reBOOTing to fix their problems.*
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- Jan 1, 1970
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TCP is a transport layer protocol (layer 4). TCP is concerned with the reliable delivery of data to the final destination (end-to-end reliability). At the receiving end, TCP must also determine which upper layer protocol the data is destined for. It determines this by looking at the destination port in the TCP header. Well known protocols like telnet, are permanently assigned to destination TCP ports (telnet is port 23). Other ports are just left available for general use (dynamic assignment). UDP also has its own set or ports and by the way, UDP ports are not the same as TCP ports.
ICMP is not a transport layer protocol. ICMP is a network layer protocol (layer 3) and is primarily concerned with routing issues (it works with the IP protocol and routing protocols). The main reason ICMP was created was to report routing failures back to the source. If an IP packet cannot continue onto the destination, an ICMP message is sent back to the source with an explanation why. ICMP doesn’t use ports (ICMP doesn’t deliver user data to upper layer protocols). Instead, ICMP uses message types and codes. For example, Destination Unreachable is message type 3. The code provides more specific information. For a type 3 message, code 0 means network unreachable, code 1 means host unreachable.
In addition to routing failures, diagnostic messages were also added to ICMP, such as echo reply and traceroute. Another feature added to ICMP was the router solicitation message, which allows hosts to discover the addresses of routers on directly attached networks. You can learn more about ICMP by reading RFC 792 at the following URL -
ICMP is not a transport layer protocol. ICMP is a network layer protocol (layer 3) and is primarily concerned with routing issues (it works with the IP protocol and routing protocols). The main reason ICMP was created was to report routing failures back to the source. If an IP packet cannot continue onto the destination, an ICMP message is sent back to the source with an explanation why. ICMP doesn’t use ports (ICMP doesn’t deliver user data to upper layer protocols). Instead, ICMP uses message types and codes. For example, Destination Unreachable is message type 3. The code provides more specific information. For a type 3 message, code 0 means network unreachable, code 1 means host unreachable.
In addition to routing failures, diagnostic messages were also added to ICMP, such as echo reply and traceroute. Another feature added to ICMP was the router solicitation message, which allows hosts to discover the addresses of routers on directly attached networks. You can learn more about ICMP by reading RFC 792 at the following URL -
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