Computer Network Reading Notes (4)

Computer Network Reading Notes (4)
Media Access Control Sub-Layer

In any broadcast network, the most critical issue is how to determine who can use the channel when multiple parties are competing to use the channel. A broadcast channel is also called a multiaccess channel or a random access channel ). It is used to determine on the multi-channel access channel that the next user's protocol belongs to a sub-layer of the data link layer, called the MAC (Medium Access Control) Sub-layer. In a LAN, the MAC Sub-layer is particularly important because many LANs use multi-channel access channels as the communication basis, while the WAN uses PPP links. Technically speaking, the MAC Sub-layer is the bottom part of the data link layer.
Channel allocation problems: 1. static channel allocation scheme in LAN and Man: The whole bandwidth is divided into N equal parts by using frequency division multiplexing (OFDM), and each user is allocated one copy, in this way, each user has its own proprietary frequency band without interference. 2. dynamic channel allocation scheme in LAN and Man: Pure Aloha-> Slot ALOHA-> continuous and non-continuous CSMA (Carrier Sense Multiple Access, carrier detection Multi-Channel Access) -> CSMA with conflict detection (also called CSMA/CD = CSMA with Collision Detection) is widely used in MAC Sub-layers in LAN and is the basis of Ethernet LAN) -> non-conflict protocol-> competitive protocol-> Wavelength Division Multiplexing (WDMA)-> Wireless LAN protocol (Maca and Macaw)
Ethernet (802.3): Ethernet means cables. There are four types of cables commonly used: coarse/fine coaxial cables, dual-gel cables and optical fibers. The Network encoding is not 0 and 1, but manchester encoding.
(P232, to be continued)