Random thoughts on Network Layer
IPv6 Protocol
The IPv6 protocol provides different types of addresses, including those for different casting(e.g., multicast, anycast, and unicast) and for different scopes (e.g., global, site-local, and link-local).
IPv6 packets consist of a basic header and number of optional extension headers. One such extension header is routing header which consist a list of all other routers including final destination. Basic header contains address of next specified router in the path. Each intermediate router swaps the next address in the list with the current destination address in the basic header.
ICMP Network Probe
This ICMP packet is the much talked about “ping” packet. What is the “echo request” used for though? Well primarily the ping packet is used to confirm if an IP address is assigned or not i.e.: is there a computer at a specific IP address? If there is then a reply will be issued by that IP address, and if not then an ICMP error message will be generated and returned.
Within the Internet Protocol, data is carried by the TCP, UDP etc. We however also need something to tell us whether the part of the Internet we are connected to or want to access is in working condition or not. This is done by ICMP. Thus all that ICMP does is perform diagnostic tasks on the Internet, and is not used to carry any data. In this sense, the structure of ICMP is a lot like IP. In fact, ICMP is always carried by the IP or encapsulated within the IP data packets.
Normally ICMP is used and implemented more in routers than in individual computers on the Internet. On the other hand, TCP is implemented in the individual computers and not in routers. ICMP is an extremely simplistic protocol. The first four bytes of any ICMP message always have the same format. The rest of the message depends upon the version of IP being used. ICMP is closely tied to IP. The new version of IP, IPv6 has a completely new ICMP protocol. The reason ICMP changes with every version of IP is because it deals with IP and routing error messages most of the time and when the base technology evolves, ICMP has to mutate to keep up.
The ICMP protocol is quite simple. In the present format the first byte is a number that tells us the Type of the ICMP packet. The second byte is called Code. From a combination of Type and Code, we can determine the exact nature of any problem on the Internet. These two bytes are followed by two bytes used for Checksum which is calculated taking into account the entire ICMP packet.
Ping – ICMP tool
In a Ping program, the first ICMP packet starts off with an 8 which stands for 'Echo Request'. This means we're asking the destination server to Echo the packet back to us when it receives it. In this way we can both time the packet and check the reliability of the link. This first byte is known as the Type Field.
The next byte is a zero and stands for the Code.
After that come two bytes for the Checksum and right after that come another two bytes for the IDentification number. The ID has to be unique, so most UNIX boxes set the ID's to the number of the current process.
The next two bytes constitute the Sequence Number.
Finally, we can add any optional data if we so desire.
The IPv6 protocol provides different types of addresses, including those for different casting(e.g., multicast, anycast, and unicast) and for different scopes (e.g., global, site-local, and link-local).
IPv6 packets consist of a basic header and number of optional extension headers. One such extension header is routing header which consist a list of all other routers including final destination. Basic header contains address of next specified router in the path. Each intermediate router swaps the next address in the list with the current destination address in the basic header.
ICMP Network Probe
This ICMP packet is the much talked about “ping” packet. What is the “echo request” used for though? Well primarily the ping packet is used to confirm if an IP address is assigned or not i.e.: is there a computer at a specific IP address? If there is then a reply will be issued by that IP address, and if not then an ICMP error message will be generated and returned.
Within the Internet Protocol, data is carried by the TCP, UDP etc. We however also need something to tell us whether the part of the Internet we are connected to or want to access is in working condition or not. This is done by ICMP. Thus all that ICMP does is perform diagnostic tasks on the Internet, and is not used to carry any data. In this sense, the structure of ICMP is a lot like IP. In fact, ICMP is always carried by the IP or encapsulated within the IP data packets.
Normally ICMP is used and implemented more in routers than in individual computers on the Internet. On the other hand, TCP is implemented in the individual computers and not in routers. ICMP is an extremely simplistic protocol. The first four bytes of any ICMP message always have the same format. The rest of the message depends upon the version of IP being used. ICMP is closely tied to IP. The new version of IP, IPv6 has a completely new ICMP protocol. The reason ICMP changes with every version of IP is because it deals with IP and routing error messages most of the time and when the base technology evolves, ICMP has to mutate to keep up.
The ICMP protocol is quite simple. In the present format the first byte is a number that tells us the Type of the ICMP packet. The second byte is called Code. From a combination of Type and Code, we can determine the exact nature of any problem on the Internet. These two bytes are followed by two bytes used for Checksum which is calculated taking into account the entire ICMP packet.
Ping – ICMP tool
In a Ping program, the first ICMP packet starts off with an 8 which stands for 'Echo Request'. This means we're asking the destination server to Echo the packet back to us when it receives it. In this way we can both time the packet and check the reliability of the link. This first byte is known as the Type Field.
The next byte is a zero and stands for the Code.
After that come two bytes for the Checksum and right after that come another two bytes for the IDentification number. The ID has to be unique, so most UNIX boxes set the ID's to the number of the current process.
The next two bytes constitute the Sequence Number.
Finally, we can add any optional data if we so desire.
posted by Ajitesh Kumar at 3:01 AM
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