Question

What are the two types of protocols used to handle multiple access issues?

Answer 1

 the introduction to this chapter, we noted that there are two types of network links: point-to-point links, and broadcast links. A point-to-point link consists of a single sender on one end of the link, and a single receiver at the other end of the link. Many link-layer protocols have been designed for point-to-point links; PPP (the point-to-point protocol) and HDLC are two such protocols that we'll cover later in this chapter. The second type of link, a broadcast link, can have multiple sending and receiving nodes all connected to the same, single, shared broadcast channel. The term "broadcast" is used here because when any one node transmits a frame, the channel broadcasts the frame and each of the other nodes receives a copy. Ethernet is probably the most widely deployed broadcast link technology; we'll cover Ethernet in detail in section 5.5. In this section we'll take step back from specific link layer protocols and first examine a problem of central importance to the data link layer: how to coordinate the access of multiple sending and receiving nodes to a shared broadcast channel – the so-called multiple access problem. Broadcast channels are often used in local area networks (LANs), networks that are geographically concentrated in a single building (or on a corporate or university campus). Thus, we'll also look at how multiple access channels are used in LANs at the end of this section.