End-to-End Layer (TCP)
The goal: Reliable, sequenced, full duplex, byte stream between the source and destination end-points.
TCP header fields:
- Source port (16-bit TCP identifier)
- Destination Port (for identifying the service requested)
- Sequence number (sequence number of the first data byte in the packet)
- Acknowledgement number (for acknowledging packets safe arrival)
- Data offset (indicates the start of data in the packet)
- Flags (e.g., URG)
- Window (indicates how much data the receiver is prepared to accept beyond the acknowledgement sequence number)
- Checksum (of the entire TCP segment)
- Urgent Pointer (indicates the starting point for “something interesting in the byte stream”)
- Options