TCP Flow Control
TCP Data Transfer
- Selective Repeat ARQ with Positive ACK
- Window slides a byte basis instead packet basis
- Dynamically advertising the window size
TCP Window Flow Control
TCP Connection Management
- Select initial sequence numbers (ISN) to protect against segments from prior connections (delayed duplicates)
- Use local clock to select ISN sequence number
- Time for clock to go through a full cycle should be greater than the maximum lifetime of a segment (MSL); Typically MSL=120 seconds
- High bandwidth connections pose a problem
Sequence Number Wraparound
- 2^32 = 4.29x10^9 bytes = 34.3x10^9 bits
- High bandwidth poses a problem; At 1 Gbps, sequence number wraparound in 34.3 seconds (< MSL that is 120 seconds).
- Timestamp option: Insert 32 bit timestamp in header of each segment
- Timestamp + sequence no → 64-bit seq. no
- Timestamp can be in TCP option clock must: