06Chapter06 - for36056_ch06.fm Page 123 Monday 10:04 PM...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
123 CHAPTER 6 LAN Topologies 6.1 INTRODUCTION Before discussing three common topologies used in LANs, we define the term LAN topology and talk about framing and addressing. Definition The term LAN topology refers to the relationships between the nodes (end-user comput- ers and connecting devices) in a network. Two or more devices connect to a link; two or more links form a topology. The topology of a network is the geometric representation of the relationship of all the links and devices (stations, repeaters, bridges, etc.) to each other. There are three basic LAN topologies: bus, ring, and star (see Figure 6.1). Although other network topologies such as the mesh and hybrid mesh can connect minicomputers and mainframes computers, they are not typically used in standard LANs. Therefore, they are not discussed in this book. There are two types of topology: physical and logical. In this chapter, the term topology refers to physical topology. Logical topology refers to the relationship between nodes in a network as seen by the software that handles data delivery from station to station. Figure 6.1 Categories of LAN topology Topologies Ring Star Bus
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
124 CHAPTER 6 LAN TOPOLOGIES Framing To control the transmission of data, all three topologies discussed here carry data in small units called frames. Each frame contains a part of the data to be sent and a header or trailer (or both). The header normally contains the sender and receiver physical addresses (at the data link layer). The header (or trailer) can also contain control information such as a sequence number or redundant information to be used in error detection. Addressing In all three topologies, an addressing mechanism ensures that a frame is received by one or more destinations. Each station is assigned a unique address. When a station sends a frame, the frame includes a source address and a destination address. When the frame is received by a station, it checks to see if the destination address matches one of its three addresses: unicast, multicast, or broadcast. Unicast Unicast addressing means one-to-one communication; a station sends a frame that is received by only one station. Multicast Multicast addressing means one-to-many communication; a station sends a frame that can be received by a selected number of stations. A group of stations can have a com- mon multicast address (which is different from their unicast addresses). When a station wants to send a frame to a group of stations, it uses the multicast address defining that particular group. Multicast addresses are normally distinguished from unicast addresses by a special bit pattern. Broadcasting Broadcast addressing means one-to-all communication; a station sends a frame that can be received by all other stations. Broadcast communication can be considered a special case of multicast communication; the group includes all of the stations. Baseband Versus Broadband Transmission
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}

Page1 / 22

06Chapter06 - for36056_ch06.fm Page 123 Monday 10:04 PM...

This preview shows document pages 1 - 3. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online