Link Layer Services
Framing, link access:
- encapsulate datagram into frame, adding header, trailer
- implement channel access if shared medium,
- ‘physical addresses’ used in frame headers to identify source, dest
- different from IP address!
Reliable delivery between two physically connected devices:
- we learned how to do this already (chapter 3)!
- seldom used on low bit error link (fiber, some twisted pair)
- wireless links: high error rates
- Q: why both link-level and end-end reliability?