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Chapter 11 - PowerPoint PPT Presentation

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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