17
edits
CS4461: Difference between revisions
Jump to navigation
Jump to search
no edit summary
No edit summary |
No edit summary |
||
|
Problem - Forwarding tables can be modified before all the info is transmitted so the paths of individual packets may differ and packets may arrive out of order.
The Internet Protocol (IP):
Datagram Format
-Version Number: 4 bits specify the IP protocol version.
-Router uses this to determine how to interpret the remainder of the packet
-Header Length: 4 bits to specify where in the IP datagram the data begins (typically 20)
-Type of Service: TOS bits set to determine priority
-Datagram Length: Total length of the IP datagram (header plus data) measured in bytes
-field is 16 bits long so max is 65535 bytes (typically 1500 bytes)
-Identifier, flags, fragmentation offset: IP fragmentation stuff
-Time-to-live: TTL ensures that datagrams don't cycle forever in routing loops
-Decreased by 1 each time it goes through a router
-Must be dropped when it hits 0
-Protocol: Used only at the dst to indicate the specific transport layer protocol
-Header checksum: Aids routers in detecting bit errors
-Src and Dst IP addresses: src creates a datagram
-puts its own IP in the src IP address field
-puts dst IP address into the dst IP address field
-Options: allow for the IP header to be extended
-Data: the payload of the packet contains the transport-layer segment to be delivered
| |||