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Chapter 11

Chapter 11. Wide Area Networking (WAN) Protocols. Defining WAN Terms. Customer Premises Equipment (CPE) is your stuff Demarcation (demarc) is end of provider’s responsibility Local loop connects demarc to central office

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Chapter 11

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  1. Chapter 11 Wide Area Networking (WAN) Protocols

  2. Defining WAN Terms • Customer Premises Equipment (CPE) is your stuff • Demarcation (demarc) is end of provider’s responsibility • Local loop connects demarc to central office • Central Office (CO) / Point of Presence (POP) connects customer to provider’s switching network • Toll network - trunk lines in WAN network

  3. WAN Connection Types Up to 45 Mbps

  4. WAN Support • Frame Relay – packet switched, 64 Kbps to 1.44 Mbps • ISDN – voice and data over phone lines • LAPB – connection oriented, good with errors, not used much • HDLC - connection oriented, proprietary • PPP – standard protocol, very flexible • ATM – simultaneous transmission of voice, video and data, uses 53 byte sized cells for sending.

  5. Serial Transmission • Cisco routers use a proprietary 60-pin serial connector • Serial links are described in frequency or cycles-per-second • Amount of data carried inside a frequency is the bandwidth • Bits-per-second that a serial line can carry

  6. DCE/DTE Equipment • DTE (Data Terminal Equipment) • Routers are (usually) DTEs • DCE (Data Communication Equipment) • CSU/DSUs are the DCEs

  7. HDLC Protocol • “High Level Data Link Control” • Bit-oriented Data Link layer ISO standard protocol • Specifies a data encapsulation method • Point-to-Point protocol for leased lines • No authentication can be used • Different HDLC versions incompatible

  8. HDLC Frame Format

  9. Point-to-Point Protocol (PPP) • Transport layer-3 packets across a Data Link layer point-to-point link • Can be used over asynchronous serial (dial-up) or synchronous serial (ISDN) media • Uses Link Control Protocol (LCP) • Builds & maintains data-link connections

  10. Point-to-Point Protocol Stack

  11. PPP Main Components • EIA/TIA-232-C - standard for serial communications • HDLC - serial link datagram encapsulation method • LCP - used in Point-to-Point connections: • Establishing • Maintaining • Terminating • NCP • Establishes & configures Network Layer protocols • Allows simultaneous use of multiple Network layer protocols

  12. LCP Configuration Options • Authentication identifies the user; PAP and CHAP • Compression helps speed transfers; Stacker and Predictor • Error detection; Quality and Magic Number • Multilink splits the load for PPP over 2+ parallel circuits (a bundle)

  13. PPP Session Establishment • Link-establishment phase – LCP packets test the link • Authentication phase (if configured) – PAP or CHAP do their stuff • Network layer protocol phase – PPP uses Network Control Protocol to encapsulate other protocols

  14. PPP Authentication Methods • Password Authentication Protocol (PAP) • Passwords sent in clear text • Remote node returns username & password • Challenge Authentication Protocol (CHAP) • Done at start-up & periodically • Challenge & Reply • Remote router sends a one-way hash ~ MD5

  15. Configuring PPP • Step #1: Configure PPP on RouterA & RouterB: Router__#config t Router__(config)#int s0 Router__(config-if)#encapsulation ppp Router__(config-if)#^Z • Step #2: Define the username & password on each router: • RouterA: RouterA(config)#username RouterB password cisco • RouterB: RouterB(config)#username RouterA password cisco NOTE: (1) Username maps to the remote router (2) Passwords must match • Step #3: Choose Authentication type for each router; CHAP/PAP Router__(Config)#int s0 Router__(config-if)#ppp authentication chap Router__(config-if)#ppp authentication pap Router__(config-if)#^Z

  16. Frame Relay • Background • High-performance WAN encapsulatuon method • OSI Physical & data Link layer • Originally designed for use across ISDN • Supported Protocols • IP, DECnet, AppleTalk, Xerox Network Service (XNS), Novell IPX, Banyan Vines, Transparent Bridging, & ISO

  17. Frame Relay • Provide a communications interface between DTE & DCE equipment • Connection-oriented Data Link layer communication • Via virtual circuits • Provides a complete path from the source to destination before sending the first frame

  18. Frame Relay Terminology

  19. Frame Relay Encapsulation • Specified on serial interfaces • Encapsulation types (choose one): • Cisco (default encapsulation type) • IETF (used between Cisco & non-Cisco devices) RouterA(config)#int s0 RouterA(config-if)#encapsulation frame relay ? ietf Use RFC1490 encapsulation <cr>

  20. Data Link Connection Identifiers (DLCIs) • Frame Relay PVCs are identified by DLCIs • IP end devices are mapped to DLCIs • Mapped dynamically or mapped by IARP • Global Significance: • Advertised to all remote sites as the same PVC • Local Significance: • DLCIs do not need to be unique • Configuration RouterA(config-if)#frame-relay interface-dlci ? <16-1007> Define a DLCI as part of the current subinterface RouterA(config-if)#frame-relay interface-dlci 16

  21. Local Management Interface (LMI) • Adds to frame relay • Allows routers to talk to frame switch • LMI messages from router to switch: • Keepalives (is data flowing?) • Multicasting (DLCI PVCs) • Multicast addressing (global significance) • Status of DLCI virtual circuits

  22. LMI Types • Three types of LMI: RouterA(config-if)#frame-relay lmi-type ? cisco ansi q933a • LMI type is auto-sensed beginning with IOS 11.2+ • Default type: cisco • Virtual circuit status: • Active – routers are routing • Inactive – router is up, remote router is not • Deleted – no LMI info is being received

  23. Sub-interfaces • Multiple virtual circuits on a single serial interface • Allows different network-layer characteristics for each sub-interface • IP routing on one sub-interface • IPX routing on another • Reduces difficulties associated with: • Partial meshed Frame Relay networks • Split Horizon protocols

  24. Partial Meshed Networks • This works on a LAN, but is messy with WANs • Have to set up PVCs for frame relay

  25. Full Mesh Networks • This works on LANs and WANs, but is very expensive • Each circuit is a separate cost

  26. Partial Mesh w/ Subinterfaces • A, B, and C are fully meshed • C and D are point to point • D and E are point to point • C and D have subinterfaces to forward packets

  27. Creating Sub-interfaces #1: Set the encapsulation on the serial interface #2: Define the subinterface RouterA(config)#int s0 RouterA(config)#encapsulation frame-relay RouterA(config)#int s0.? <0-4294967295> Serial interface number RouterA(config)#int s0.16 ? multipoint Treat as a multipoint link point-to-point Treat as a point-to-point link

  28. Mapping Frame Relay • Necessary for IP end devices to communicate • Addresses must be mapped to the DLCIs • Methods: • Frame Relay map command • Inverse-arp function

  29. Using the map command RouterA(config)#int s0 RouterA(config-if)#encap frame RouterA(config-if)#int s0.16 point-to-point RouterA(config-if)#no inverse-arp RouterA(config-if)#ip address 172.16.30.1 255.255.255.0 RouterA(config-if)#frame-relay map ip 172.16.30.17 16 ietf broadcast RouterA(config-if)#frame-relay map ip 172.16.30.18 17 broadcast RouterA(config-if)#frame-relay map ip 172.16.30.19 18 See page 552 for full explanation

  30. Using inverse arp command RouterA(config)#int s0.16 point-to-point RouterA(config-if)#encap frame-relay ietf RouterA(config-if)#ip address 172.16.30.1 255.255.255.0

  31. Congestion Control • What if frame relay circuit gets too busy? • Discard Eligibility (DE) drops packets that are eligible • Forward-Explicit Congestion Notification (FECN) alerts destination DCE that circuit is busy • Backward-Explicit Congestion Notification (BECN) alerts source router to slow down

  32. Committed Information Rate (CIR) • Allows customers to purchase amounts of bandwidth lower than what they might need • CIR is guaranteed rate, extra traffic is not guaranteed • Cost savings • Good for bursty traffic • Not good for constant amounts of data transmission

  33. Monitoring Frame Relay RouterA>sho frame ? ip show frame relay IP statistics lmi show frame relay lmi statistics map Frame-Relay map table pvc show frame relay pvc statistics route show frame relay route traffic Frame-Relay protocol statistics RouterA#sho int s0 RouterB#show frame map Router#debug frame-relay lmi

  34. ISDN • Integrated Services Digital Network • Used by Telecoms to simultaneously send voice, data, and music, etc. over current phone lines • Uses PPP typically

  35. ISDN • Uses BRI (Basic Rate Interface) • 2-64 K channels for data • 1-16 K signaling channel • Uses terminals • TE1 – Understand ISDN standards • TE2 – predate standards and use an adapter • NT1 – converts 4-wire to 2-wire ISDN • NT2 – Switch or PBX (rare) • TA – adapter for ISDN

  36. BRI • Basic Rate Interface • Operates at 64 Kbps • Total bandwidth for ISDN BRI is 144 Kbps (64x2 and 16) • In NA and Japan, have PRI (Primary Rate Interface) • Operates at 1.544 Kbps (23x64 and 64) • In Europe and AUstralia, have PRI (Primary Rate Interface) • Operates at 2.048 Kbps (30x64 and 64)

  37. DDR • Dial-On-Demand Routing • As needed basis • Need the equipment in order to run

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