Usually the IP protocol stack will set the size of the IP packets to fit into their Ethernet interfaces. However, we know that Ethernet, for example, uses a maximum transmission unit size of 1500 bytes. In IPv4, datagram size is limited by the Total Length field with is 16 bits. RFC 6864 clarifies that the primary purpose of the ID Field is in support of fragmentation and reassembly. The first answer defining the IP ID field has to do with IP packet fragmentation. Here is a graphical representation of the IPv4 header: This uniqueness is currently specified as for all datagrams, regardless of fragmentation settings. As currently specified, all datagrams between a source and destination of a given protocol must have unique IPv4 ID values over a period of this MDL, which is typically interpreted as two minutes and is related to the recommended reassembly timeout. In IPv4, the Identification (ID) field is a 16-bit value that is unique for every datagram for a given source address, destination address, and protocol, such that it does not repeat within the maximum datagram lifetime (MDL). RFC 6864 updated RFC’s 791, 1122, and 2003 to clarify the definition of the IPv4 ID field: While many have tried to answer the question in various articles on the Internet, I thought the question deserved a clear answer to the question. What exactly is the purpose of the IP ID field? This is actually a great question. 4 of 5 - 7 votes Thank you for rating this article.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |