C6 Flashcards
what OH fields are copied from IH
TOS, DF
What fields of IH are not the same as original datagram
TTL, Checksum
TTL inner header
at the start of tunnel, TTL is decreased by 1
if TTL is not 0, it is inserted into IH
checksum is re calculated
otherwise, if ttl is 0 no more ip in ip encapsulation and an ICMP message is sent back to the source
what is flow control?
a faster sender will not congest a slower receiver
What is the reliability of a protocol?
low error rate, retransmission in case of errors
What is the TCP header length?
20 bytes - 60 bytes
Source port TCP header
16 bit TSAP
source socket = source ip address + source port + communication descriptor
Destination port TCP header
16 bit TSAP
destination socket = destination IP address + destination port + communication descriptor
Sequence Number TCP header
32 bit, referes to the first data byte of the current TCP segment
ACK number TCP header
piggybacking acknowledgement referring the next data byte expected