The Internet Manage Message Protocol communicates errors messages in between systems that need attention. This error is not generally at the user degree, the error is handled by the software layer. In the OSI Reference design, ICMPs are generally considered component of the IP layer.

To place to plain and easy, ICMP messages are sent “behind the scenes” to your programs to tell them if there is a issue with the connection or transfer of information. These messages tell your software to change what they are doing, change how they are sending and essentially give them an error code on how they can successfully repair their issues.

ICMPs’ are sent in a regular IP datagram, this datagram contains an IP header of 20 () bytes and then the ICMP message. There are fifteen values for the type area of the datagram which identifies the type of ICMP message. The “code” part of the datagram specifies the situation of the “type” even further. This sounds a bit perplexing at initial, but you have two main categories, the primary “issue,” and then a secondary much more in depth appear at that issue. This will all make much more feeling when you appear at information beneath.

Type , code – echo reply

Type 3 (destination unreachable)
Type 3, code – network unreachable
Type 3, code one – host unreachable
Type 3, code 2 – protocol unreachable
Type 3, code 3 – port unreachable
Type 3, code 4 – fragmention needed
Type 3, code five – source route failed
Type 3, code six – destination network mysterious
Type 3, code seven – destination host mysterious
Type 3, code 8 – source host isolated
Type 3, code 9 – destination network administratively prohibited
Type 3, code 10 – destination host administratively prohibited
Type 3, code 11 – network unreachable for TOS
Type 3, code 12 – host unreachable for TOS
Type 3, code thirteen – communication administratively prohibited by filtering
Type 3, code 14 – host precedence violation
Type 3, code 15 – precedence cutoff in impact

Type 4, code – source quench

Type five (redirects)
Type five, code – redirect for network
Type five, code one – redirect for host
Type five, code 2 – redirect for type of service and network
Type five, code 3 – redirect for type of service and host

Type 8, code – echo request

Type 9, code – router advertisement

Type 10, code – router solicitation

Type 11 (time exceeded)
Type 11, code – time to live (TTL) equals during transit
Type 11, code one – time to live (TTL) equals during reassembly

Type 12 (parameter issue)
Type 12, code – IP header bad
Type 12, code one – needed choice lacking
Type thirteen, code – timestamp request

Type 14, code – timestamp reply

Type 15, code – information request

Type 16, code – information reply

Type 17, code – deal with mask request

Type eighteen, code – deal with mask reply

As you can see from the over information, the primary “type” groups are the main issue, with the “code” further specifying the issue. A lot of this stuff doesn’t make feeling to the human end-user anyway, but it indicates a lot to the software developers who use these requests to repair issues in their coding.

ICMP’s are a good behind the scenes helper that are great to have their, but be thankful you don’t truly have to offer with them. For even much more comprehensive information on the Internet Manage Message Protocol (ICMP) the protocol is defined in RFC 792.

Ken Dennis
http://KenDennis-RSS.homeip.net/