ICMP Protocol - Internet Control Message Protocol

The Internet Control Message Protocol communicates errors messages between systems that require attention. This error is not usually at the user level, the error is handled by the application layer. In the OSI Reference model, ICMPs are generally considered part of the IP layer.

To put to plain and simple, ICMP messages are sent "behind the scenes" to your applications to tell them if there is a problem with the connection or transfer of data. These messages tell your application to change what they are doing, change how they are sending and basically give them an error code on how they can successfully fix their problems.

ICMPs' are sent in a standard IP datagram, this datagram contains an IP header of twenty (20) bytes and then the ICMP message. There are fifteen values for the type field of the datagram which identifies the type of ICMP message. The "code" portion of the datagram specifies the condition of the "type" even further. This sounds a bit confusing at first, but you have two major categories, the primary "problem," and then a secondary more in depth look at that problem. This will all make more sense when you look at information below.

Type 0, code 0 - echo reply

Type 3 (destination unreachable)
Type 3, code 0 - network unreachable
Type 3, code 1 - host unreachable
Type 3, code 2 - protocol unreachable
Type 3, code 3 - port unreachable
Type 3, code 4 - fragmention needed
Type 3, code 5 - source route failed
Type 3, code 6 - destination network unknown
Type 3, code 7 - destination host unknown
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 13 - communication administratively prohibited by filtering
Type 3, code 14 - host precedence violation
Type 3, code 15 - precedence cutoff in effect

Type 4, code 0 - source quench

Type 5 (redirects)
Type 5, code 0 - redirect for network
Type 5, code 1 - redirect for host
Type 5, code 2 - redirect for type of service and network
Type 5, code 3 - redirect for type of service and host

Type 8, code 0 - echo request

Type 9, code 0 - router advertisement

Type 10, code 0 - router solicitation

Type 11 (time exceeded)
Type 11, code 0 - time to live (TTL) equals 0 during transit
Type 11, code 1 - time to live (TTL) equals 0 during reassembly

Type 12 (parameter problem)
Type 12, code 0 - IP header bad
Type 12, code 1 - required option missing
Type 13, code 0 - timestamp request

Type 14, code 0 - timestamp reply

Type 15, code 0 - information request

Type 16, code 0 - information reply

Type 17, code 0 - address mask request

Type 18, code 0 - address mask reply

As you can see from the above information, the primary "type" groups are the main problem, with the "code" further specifying the problem. Much of this stuff doesn't make sense to the human end-user anyway, but it means a lot to the software developers who use these requests to fix problems in their coding.

ICMP's are a nice behind the scenes helper that are good to have their, but be thankful you don't really have to deal with them. For even more detailed information on the Internet Control Message Protocol (ICMP) the protocol is defined in RFC 792.

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

---

3G EV-DO or How the Internet Got Its Wings!

The Internet, as most people know it, is history.It just... Read More

Internet ISPs

Choosing an internet ISP is often a rash and impulsive... Read More

How to Secure your DSl / Cable Internet Connection Against Malicious Attacks

Securing your Windows Xp computer is done by achieving two... Read More

What is Broadband?

Defining broadband can get complicatedThere are many different takes on... Read More

The Coming Television Revolution

The revolution is just getting started and will be begin... Read More

Broadband Features

Internet service providers are becoming more and more present as... Read More

Cheap Internet Access

For anyone trying to get the cheapest internet available, there... Read More

How to Troubleshoot Your Internet Connection for DSL or Cable Service

One of the common problems among internet users is testing... Read More

Beta Testing First Mobile Internet Satellite Broadband, Part III

Back in 1999 when we beta tested the first wireless... Read More

Its On! (Free Internet TV - Watch TV Online)

Get ready because "there's going to be television out the... Read More

Beta Testing First Mobile Internet Satellite Broadband, Part I

Being on the road has its advantages; the freedom is... Read More

How to Test Your DSL and Cable Internet Connection Speed

There are two measured elements that determine your internet connection... Read More

Wireless Network Hammerin

The wireless network in my house went haywire. It worked... Read More

Webmail - What are the Benefits?

There are so many different webmail services on the internet,... Read More

How to Get Broadband

Getting broadband services getting easy, but research still required.Broadband Internet... Read More

Unlimited Bandwidth and Overselling

One of the most controversial topics surrounding web hosting is... Read More

Broadband Connection to the Central Sun

You may have noticed the expansion of consciousness that has... Read More

BT Broadband

Approximately 4 million people in the UK use ADSL with... Read More

Mind Machine Interfacing

SQUID:In 1984 I was partnered with a Cable TV engineer... Read More

Chat-less

Are you suddenly chat-less now that Yahoo has shut down... Read More

Broadband - Will it Affect Your Online Marketing Future?

The coming age of general Broadband use bearing down upon... Read More

Internet Service Providers

Internet Service Provider or ISP is a company that provides... Read More

Whois Protocol - TCP/IP Suite

The Whois protocol is an information service not unlike the... Read More

Wi-Fi Hotspot Security

You've set up your Boingo account, you're hanging out at... Read More

Why Choose Dial Up ISP Services

Dial up ISP service is the cheapest choice of any... Read More

How to Choose Best ISP for Your Needs

Well, the Internet access industry is starting to shake its... Read More

Google Brings Millions of Hard-to-Find Library Books to Your Fingertips

Millions of hard-to-find books from five major libraries will soon... Read More

Broadband is State-of-the-Art Internet Access: How Can a Broadband Cable Benefit You?

We are now well ensconced in a time when the... Read More

Google Talk Reviewed

So you're sick and tired of AOL Instant Messenger. You're... Read More

DSL Internet is a Simple and Easy Way to Get Fast Internet Service

DSL ? which stands for Digital Subscriber Line ? is... Read More

Long Arm of the Law Reaches New Internet (RIAA, Internet-2, i2hub Lawsuit)

Have you heard of the new Internet? It's called Internet... Read More

Understanding Broadband - Are You Ready To Upgrade?

Are you ready to upgrade your residential service to DSL... Read More

Dreams Come True With The Help Of Global Consciousness On The Internet

Dreams. There are two types of dreams: 1. When you... Read More