12.2 Peer-to-Peer Networking

Another popular home network application is for sharing files on hard disk drives, printers, scanners, cameras, and the like among multiple PCs. Figure 12.7 shows how multiple PCs in a household can be interconnected via a Category 5 twisted pair based 10BaseT/100BaseTX Ethernet. To locate the Ethernet hub at a central location, a star or home-run telephone wiring topology with data-grade cables is required. Because only two pairs are used by the Ethernet, conventional telephone sets can still be connected to the telephone service using one remaining pair of the same Category 5 twisted pair cable. On each wall plate, one RJ-45 jack connected to Orange/Orange stripe and Green/Green stripe pairs is used for data networking, and another RJ-11 jack connected to the Blue/Blue stripe pair is used for telephone service. Home-run Category 5 wiring becomes more popular for newly constructed homes. Without home-run data-grade cable wiring, a home network can still be implemented using HomePNA based on existing regular telephone wiring, HomePlug based on in-house electrical wiring, or wireless technologies such as HomeRF and IEEE 802.11.

Figure 12.7. Home Networking via 10/100BaseT Ethernet

graphics/12fig07.gif

Networking among multiple PCs in a household or a small office environment over an Ethernet, or other Ethernet family of network systems including wireless Ethernet (IEEE 802.11), HomePNA, and HomePlug is usually implemented via the NetBEUI protocol [5] available through Windows operating systems. NetBEUI can be installed using the Add Protocol option and selecting the Network icon within the Control Panel. In addition, each PC on a NetBEUI-based network should choose the same group name. NetBEUI can provide a peer-to-peer network where no PC is required to act as a server and therefore avoids associated network set-up and management process. A laptop PC can easily become a part of this peer-to-peer network as soon as its Ethernet connection is plugged in and the machine is turned on, provided the NetBEUI is properly installed. With NetBEUI, PCs can share files and printers but not Internet access. (NetBEUI stands for NetBIOS Extended User Interface and NetBIOS stands for Network Basic Input Output System.) The NetBIOS interface was originally developed by Sytec, Inc., for IBM in 1983 and was designed to be an extension to the PC BIOS to provide network services. The NetBIOS interface consists of a set of protocols for name management, connectionless, and connection-oriented communications. Most recently, NetBEUI has been referred to as the NBF (NetBEUI Frame or NetBIOS Frame) protocol.

Each node in an NBF-based network can be identified by a name of 16 bytes instead of an address as those of Internet or Ethernet. Multiple names can be associated with a single node of different application processes. Because there is no hierarchy in an NBF name, routing is not directly available except over the token ring network or through encapsulation. For applications in home or small office environments of up to a few hundred PCs, this does not pose a serious problem. NBF name creation and registration are carried out through the Name Management Protocol (NMP). A node broadcasts its intention to use a new name several times and the name is added to the local name table if no other node contests the name claim. NMP is implemented over the Ethernet LLC layer with four name management frames of 44 bytes each: Add Name Query, Add Group Name Query, Add Name Response, and Name In Conflict. Connectionless packets can be transmitted over an NBF net work via its User Datagram Protocol (UDP). A Datagram frame consists of a 44-byte header including receiver and sender names followed by a payload of up to 468 bytes for a total maximum size of 512 bytes. A Datagram Broadcast frame over Ethernet LLC also consists of a 44-byte header including only the sender name followed by a payload. Connections oriented communication can be establish over an NBF network via its Session Management Protocol (SMP). Under SMP, one node calls another to establish a session. The session continues until being terminated by either node. There are two frames of 44 bytes each for session establishment: Name Query and Name Recognized. There are also four short (14 bytes) session-established frames: Session Alive, Session Confirm, Session End, and Session Initialize. There are Data Ack, Data First Middle, Data Only Last, No Receive, Receive Outstanding, and Receive Continue frames also defined for SMP. The Diagnostic and Monitoring Protocol (DMP) is defined to obtain status information about nodes on an NBF network. There are four 44-byte frames Status Query, Status Response, Terminate Trace, and Terminate Local & Remote Trace defined under DMP. The UDP, SMP, and DMP frames are all defined over the Ethernet LLC layer.



Home Network Basis(c) Transmission Environments and Wired/Wireless Protocols
Home Networking Basis: Transmission Environments and Wired/Wireless Protocols
ISBN: 0130165115
EAN: 2147483647
Year: 2006
Pages: 97

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