Tcp Ip Protocol Questions Long
IP packet fragmentation is a process used in the TCP/IP protocol to break down large IP packets into smaller fragments that can be transmitted over networks with smaller maximum transmission unit (MTU) sizes. This fragmentation process is necessary when the size of the IP packet exceeds the maximum size allowed by a network link or router along the path.
When a source device wants to send a large IP packet, it first checks the MTU of the outgoing network interface. If the packet size exceeds the MTU, fragmentation is required. The source device then divides the original IP packet into smaller fragments, each with a smaller size that fits within the MTU of the network link.
Each fragment contains a fragment header, which includes information such as the identification number, offset, and a flag indicating whether more fragments are expected. The identification number is used to identify which fragments belong to the same original IP packet.
Once the fragments are created, they are individually encapsulated into separate IP packets and sent over the network. Each fragment is treated as an independent IP packet and can take different paths to reach the destination.
At the destination, the receiving device collects all the fragments based on their identification number. It uses the offset information in the fragment header to determine the correct order of the fragments. The receiving device buffers the fragments until it receives all the expected fragments or until a timeout occurs.
Once all the fragments are received, the receiving device reassembles them in the correct order to reconstruct the original IP packet. It uses the offset information to determine the position of each fragment within the original packet. The reassembled packet is then passed to the higher layers of the TCP/IP protocol stack for further processing.
It is important to note that IP packet fragmentation can introduce additional overhead and can impact network performance. Therefore, it is generally recommended to avoid fragmentation whenever possible by adjusting the packet size or using techniques such as Path MTU Discovery to determine the maximum size allowed by the network path.