WAN TECHNOLOGIES by Gorvam saddar

INTRODUCTION TO WAN TECHNOLOGIES

This chapter introduces the various protocols and technologies used in wide-area network (WAN) environments. Topics summarized here include point-to-point links, circuit switching, packet switching, virtual circuits, dialup services, and WAN devices. Chapters in Part III, "WAN Protocols," address specific technologies in more detail.

What Is a WAN?

A WAN is a data communications network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. Figure 3-1 illustrates the relationship between the common WAN technologies and the OSI model.....

OSI REFRENCE MODEL - clear conclusion complete very easy by Gorvam Saddar

THE OSI REFERENCE MODEL

ALL PEOPLE SEEM TO NEED DATA PROCESSING

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LAYER WHAT THE LAYER IS RESPONSIBLE FOR/SERVICES ETC. CORRESPONDING DEVICES CORRESPONDING PROTOCOLS Application 7 1. Interface between the user & the computer (applications & Gateways). Provides services that directly support user applications, such as the USER INTERFACE, E-MAIL, FILE TRANSFER, TERMINAL EMULATION, DATABASE ACCESS, etc. 2. API incorporated in this layer 3. Allows applications to use the network. 4. Handles Network access, flow control & error recovery. 5. Messages are sent between layers. Gateways (can work at all layers) · SNMP · FTP · TELNET · WWW · HTTP · SMB · NCP · TCP · TFTP · NFS · SMTP