two types of links:
1. point to point
2.broadcast(shared wire or medium)
-Multiple access protocol:
distributed algorithm that determines how nodes share channel, i.e., determine when node can transmit
communication about channel sharing must use channel itself!
-MAC protocols: taxonomy
three broad classes:
§ channel partitioning ( divide channel into smaller “pieces” (time slots, frequency, code) • allocate piece to node for exclusive use)
TDMA: time division multiple access
FDMA: frequency division multiple access
§ random access (channel not divided, allow collisions • “recover” from collisions）
slotted ALOHA
ALOHA
CSMA: listen before transmit: if channel sensed idle: transmit entire frame; if channel sensed busy, defer transmission; human analogy: don’t interrupt others!
CSMA/CD:collision detection: carrier sensing, deferral as in CSMA; collisions detected within short time; colliding transmissions aborted, reducing channel wastage
CSMA/CA
§ “taking turns”( nodes take turns, but nodes with more to send can take longer turns )
Summary of MAC protocols
§ channel partitioning, by time, frequency or code
• Time Division, Frequency Division
§ random access (dynamic),
• ALOHA, S-ALOHA, CSMA, CSMA/CD
• carrier sensing: easy in some technologies (wire), hard in others (wireless)
• CSMA/CD used in Ethernet
• CSMA/CA used in 802.11
§ taking turns
• polling from central site, token passing
• Bluetooth, FDDI, token ring
ARP:https://blog.csdn.net/u014042372/article/details/80564594