1 / 56

Chap 2 WANs and Routers

Chap 2 WANs and Routers. Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology andres@dlit.edu.tw http://www.cse.dlit.edu.tw/~andres. Overview. WAN devices, technologies, and standards The function of a router in a WAN. WANs.

storm
Télécharger la présentation

Chap 2 WANs and Routers

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chap 2 WANs and Routers Andres, Wen-Yuan Liao Department of Computer Science and Engineering De Lin Institute of Technology andres@dlit.edu.tw http://www.cse.dlit.edu.tw/~andres

  2. Overview • WAN devices, technologies, and standards • The function of a router in a WAN

  3. WANs • WANs and devices • WAN standards • WAN technologies

  4. WANs and devices • Operates at the physical layer and the data link layer • Interconnects LANs that are usually separated by large geographic areas

  5. WANs and devices • Provide for the exchange of data packets/frames between routers/bridges and the LANs they support

  6. WAN Devices • Routers -- offer many services, including internetworking and WAN interface ports • Switches -- connect to WAN bandwidth for voice, data, and video communication

  7. WAN Devices • Channel service units/digital service units (CSU/DSUs) that interface T1/E1 services • Terminal Adapters/Network Termination 1 (TA/NT1s) that interface ISDN services

  8. WAN Devices • Communication servers -- concentrate dial-in and dial-out user communication • Modems -- interface voice-grade services

  9. WAN Standards

  10. WAN Standards • WAN physical layer protocols describe how to provide electrical, mechanical, operational, and functional connections for WAN services

  11. WAN Standards • WAN data link protocols describe how frames are carried between systems on a single data link

  12. WAN physical layer • Describes the interface between the data terminal equipment (DTE) and the data circuit-terminating equipment (DCE)

  13. WAN physical layer • DCE: service provider • modem or a CSU/DSU • DTE: the attached device

  14. EIA/TIA-232 EIA/TIA-449 V.24 V.35 X.21 G.703 EIA-530 Physical layer standards

  15. Data link encapsulations • HDLC -- IEEE standard • May not be compatible with different vendors • Supports both point-to-point and multipoint configurations with minimal overhead 

  16. Data link encapsulations • Frame Relay -- uses high-quality digital facilities • Uses simplified framing with no error correction mechanisms • Send Layer 2 information much more rapidly than other WAN protocols

  17. Data link encapsulations • PPP -- described by RFC 1661 • Contains a protocol field to identify the network layer protocol

  18. Data link encapsulations • Simple Data Link Control Protocol (SDLC) • An IBM-designed WAN DL protocol for SNA • Being replaced by the more versatile HDLC • Serial Line Interface Protocol (SLIP) • Popular WAN DL protocol (IP packets) • Being replaced by the more versatile PPP

  19. Data link encapsulations • Link Access Procedure Balanced (LAPB) • A data link protocol used by X.25 • Has extensive error checking capabilities • Link Access Procedure D-channel (LAPD) • The WAN DL protocol used for signaling and call setup on an ISDN D-channel • Data transmissions take place on the ISDN B channels

  20. Data link encapsulations • Link Access Procedure Frame (LAPF) • For Frame-Mode Bearer Services • A WAN DL protocol, similar to LAPD, used with frame relay technologies

  21. WAN technologies • Circuit-switched • Cell-switched • Dedicated digital • Analog services

  22. Circuit-Switched Services • POTS (Plain Old Telephone Service) • Not a computer data service, but included • Narrowband ISDN • The first all-digital dial-up service • 128 kbps (BRI) • 3 Mbps (PRI)

  23. Packet-Switched Services • X.25 • An older technology, but still widely used • Has extensive error-checking capabilities • Make it reliable but limits its bandwidth • 2 Mbps (maximum)

  24. Frame Relay • A packet-switched version of Narrowband ISDN • More efficient than X.25, but with similar services • Maximum bandwidth is 44.736 Mbps • 56kbps and 384kbps are extremely popular

  25. Cell-Switched Services • ATM (Asynchronous Transfer Mode) • Closely related to broadband ISDN • An increasingly important WAN/LAN • Small, fixed length (53 byte) frames • Maximum bandwidth is 622 Mbps

  26. Cell-Switched Services • SMDS (Switched Multimegabit Data Service) • Closely related to ATM • Typically used in MANs • Maximum bandwidth is 44.736 Mbps • Usage not very widespread; cost is relatively high

  27. Dedicated Digital Services • T series of services in the U.S • E series of services in Europe • T1 -- 1.544 Mbps • T3 -- 44.736 Mbps • E1 -- 2.048 Mbps • E3 -- 34.368 Mbps

  28. Dedicated Digital Services • xDSL • DSL: Digital Subscriber Line • x: a family of technologies • A new and developing WAN technology (home use)

  29. Dedicated Digital Services • xDSL • Bandwidth decreases with increasing distance from the phone companies equipment • Top speeds of 51.84 Mbps (near a phone company office) • From 100s of kbps to several Mbps)

  30. Dedicated Digital Services • HDSL -- high-bit-rate DSL • SDSL -- single-line DSL • ADSL -- asymmetric DSL • VDSL -- very-high-bit-rate DSL • RADSL -- rate adaptive DSL

  31. Dedicated Digital Services • SONET (Synchronous Optical Network) • A family of very high-speed physical layer technologies • For optical fiber, also for copper cables

  32. Dedicated Digital Services • SONET • OC (optical carrier) levels: 51.84 Mbps (OC-1) to 9,952 Mbps (OC-192) • Wavelength division multiplexing (WDM) • Usage is widespread among Internet backbone entities

  33. Other WAN Services • Dial-up modems (switched analog) • Maximum bandwidth approx. 56 kbps • Cable modems (shared analog) • Put data signals on the same cable as television signals

  34. Other WAN Services • Increase in popularity in regions that have large amounts of existing cable TV coaxial cable (90% of homes in U.S.) • Maximum bandwidth can be 10 Mbps • Degrades as more users

  35. Other WAN Services • Wireless • The signals are electromagnetic waves • Terrestrial • Bandwidths typically in the 11 Mbps range (e.g. microwave) • Cost is relatively low; line-of-sight is usually required

  36. Other WAN Services • Satellite • Serve mobile users and remote users • Usage is widespread; cost is high

  37. WANs and Routers • Router basics • The function of a router in a WAN

  38. Router basics • Routers need the Internetworking Operating Software (IOS) to run configuration files • Selects the best paths and manages the switching of packets • Network layer

  39. Internal configuration components • RAM/DRAM • Stores routing tables, ARP cache, fast-switching cache, packet buffering (shared RAM), and packet hold queues • Provides temporary and/or running memory • Be lost when you power down or restart

  40. Internal configuration components • NVRAM -- nonvolatile RAM • Stores a router’s backup/startup configuration file • Content remains when you power down or restart

  41. Internal configuration components • Flash -- Erasable, reprogrammable ROM • Hold the operating system image and microcode • Update software without removing and replacing chips on the processor • Content remains when you power down • Store multiple versions of IOS software

  42. Internal configuration components • ROM • Contains power-on diagnostics, a bootstrap program, and operating system software • Software upgrades: replacing pluggable chips

  43. Internal configuration components • Interface • Network connection through which packets enter and exit a router • It can be on the motherboard or on a separate interface module

  44. The function of a router in a WAN • While routers can be used to segment LAN devices, their major use is as WAN devices • Routers have both LAN and WAN interfaces

More Related