IP Datagram Header Components Flashcards
How many parts make up an IP Datagram?
14
What is the first field? What is its purpose? How large is it in bits?
The first field indicates the Version of Internet Protocol being used and is four bits long.
What is the second field? What is its purpose? How large is it in bits?
The Header Length field declares how long the entire header will be and is four bits. This is almost always 20 bytes in length when dealing with IPv4.
What is the third field? What is its purpose? How large is it in bits?
The Service Type field specify details about QoS technologies and is eight bits long.
What is the fourth field? What is its purpose? How large is it in bits?
The Total Length field indicates the total length of the IP datagram it’s attached to and is 16 bits long.
What is the fifth field? What is its purpose? How large is it in bits?
The Identification field is a 16 bit number used to group messages together. When the total amount of data that needs to be sent exceeds the limit of a single datagram (16 bits), the IP layer needs to split this data into separate parts; the ID field is then used so that the receiving end understands that every packet with the same value in the ID field is part of the same transmission.
What is the sixth field? What is its purpose? How large is it in bits?
The Flag field is used to indicate if a datagram is allowed to be fragmented or indicate that the datagram has already been fragmented and is 4 bits long.
What is the seventh field? What is its purpose? How large is it in bits?
The Fragmentation Offset field contains values used by the receiving end to take all of the parts of a fragmented packet and put them back together in the correct order and is 12 bits long.
What is the eighth field? What is its purpose? How large is it in bits?
The Time to Live or TTL field indicates how many router hops a datagram can traverse before its thrown away and is 8 bits long; this is to prevent datagrams from looping endlessly between routers.
What is the ninth field? What is its purpose? How large is it in bits?
The Protocol field contains data about what transport layer protocol is being used and is 8 bits long.
What is the tenth field? What is its purpose? How large is it in bits?
The Checksum field is a checksum of the contents of the entire IP datagram header and is 16 bits long.
What is the eleventh field? What is its purpose? How large is it in bits?
The Source IP Address field simply lists the source’s IP address and is 32 bits long.
What is the twelfth field? What is its purpose? How large is it in bits?
The Destination IP Address simply lists the destination’s IP address and is 32 bits long.
What is the thirteenth field? What is its purpose? How large is it in bits?
The IP Options field is used to set special characteristics for datagrams primarily used for testing purposes and is both optional to include in the datagram and variable in size.
What is the fourteenth field? What is its purpose? How large is it in bits?
The Padding field is a series of zeros to ensure the header is the correct total size (since the IP Options field is optional to include).
