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CCNA Guide to Cisco Networking

CCNA Guide to Cisco Networking. Chapter 11: PPP and ISDN. Objectives. Describe PPP encapsulation Configure PPP encapsulation and its options Describe and enable PPP multilink Explain how to implement ISDN BRI on Cisco routers Configure an ISDN BRI connection. PPP.

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CCNA Guide to Cisco Networking

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  1. CCNA Guide to Cisco Networking Chapter 11: PPP and ISDN

  2. Objectives • Describe PPP encapsulation • Configure PPP encapsulation and its options • Describe and enable PPP multilink • Explain how to implement ISDN BRI on Cisco routers • Configure an ISDN BRI connection CCNA Guide to Cisco Networking

  3. PPP • Internet standard protocol • Considered a peer technology • Used over dial-up or leased lines • Support for multiple Network layer protocols • Most widely use WAN connection protocol CCNA Guide to Cisco Networking

  4. PPP (continued) • SLIP • Supports • Encryption • Compression • Error correction • Works with synchronous and asynchronous connections • Can be applied on many different physical interfaces • Asynchronous serial • ISDN synchronous • High-Speed Serial Interface (HSSI) CCNA Guide to Cisco Networking

  5. PPP In The Protocol Stack • Link control protocol • Data Link layer • Establish • Configure • Test • Network control protocols (NCPs) • Allows multiple protocols to used at the same time • IP control protocol (IPCP) • IPX control protocol (IPXCP) • AppleTalk control protocol (ATCP) CCNA Guide to Cisco Networking

  6. PPP In The Protocol Stack (continued) CCNA Guide to Cisco Networking

  7. Frame Format CCNA Guide to Cisco Networking

  8. Frame Format (continued) • Frame fields of PPP • Flag: Binary sequence 01111110, which indicates the beginning of the frame • Address: Binary sequence 11111111; because PPP is used to create a point-to- point connection, there is no need for PPP to assign an individual address for each host • Control: Binary sequence 00000011, which indicates that the transmission of user data will not be sequenced and is to be delivered over a connectionless link • Protocol: Two bytes used to identify the protocol that is encapsulated CCNA Guide to Cisco Networking

  9. Frame Format (continued) • Frame fields of PPP (continued) • LCP orData: The LCP field is also known as the Data field, which is the location contains the LCP information and the data that has been encapsulated from the higher layers • Frame Check Sequence (FCS): Cyclical redundancy check (CRC) to verify the integrity of the frame • Flag: Binary sequence 01111110, which identifies the end of the data frame CCNA Guide to Cisco Networking

  10. LCP • LCP field of the PPP packet may include • Asynchronous character map • Maximum receive unit size • Compression • Authentication • PAP • CHAP • Magic number • Link quality monitoring (LQM) • Multilink CCNA Guide to Cisco Networking

  11. LCP Link Configuration • LCP link configuration process includes • Link establishment • Authentication (optional) • Link-quality determination (optional) • Network layer protocol configuration negotiation • Link termination CCNA Guide to Cisco Networking

  12. Establishing PPP Communications • Link establishment phase • First phase • Testing and configuration of the data link • Second phase • Optional authentication • PAP and CHAP • Third phase • Network layer protocol configuration negotiation • Data packet transfer may begin CCNA Guide to Cisco Networking

  13. Establishing PPP Communications (continued) CCNA Guide to Cisco Networking

  14. Configuring PPP Authentication • Configure PPP authentication on each PPP host • Link flapping will occur if authentication is only on one host • PAP • Two-way handshake • Usernames and Passwords sent in clear text • CHAP • Three-way handshake • Usernames and passwords are protected CCNA Guide to Cisco Networking

  15. Configuring PPP Authentication (continued) CCNA Guide to Cisco Networking

  16. Configuring PPP Authentication (continued) CCNA Guide to Cisco Networking

  17. Configuring PPP Authentication (continued) CCNA Guide to Cisco Networking

  18. Confirming PPP Communications • “show interface” command • Router# show interface serial 0/0 CCNA Guide to Cisco Networking

  19. ISDN • Circuit-switched service • Existing telephone service • Data • Voice • Video • Audio transmission • Faster than traditional modem speeds CCNA Guide to Cisco Networking

  20. ISDN (continued) • Basic Rate Interface (BRI) • 128 kbps total data transfer bandwidth • 2 B-channels • Bearer channel for data transfer • 64 kbps • 1 D-channel • Delta or data channel for signaling • Out of band signaling • Link Access Procedure-D • 16 kbps CCNA Guide to Cisco Networking

  21. ISDN (continued) • Primary Rate Interface (PRI) • 1.544 mbps total data transfer bandwidth • 23 B-channels • Bearer channel for data transfer • 64 kbps • 1 D-channel • Delta or data channel for signaling • Out of band signaling • Link Access Procedure-D • 64 kbps CCNA Guide to Cisco Networking

  22. ISDN (continued) CCNA Guide to Cisco Networking

  23. ISDN Standards CCNA Guide to Cisco Networking

  24. ISDN Operations CCNA Guide to Cisco Networking

  25. ISDN Operations (continued) • Functions and references • Function groups • Terminal adapter • Terminal equipment 1 (TE1) • Terminal equipment 2 (TE2) • Network termination 1 (NT1) • Network termination 2 (NT2) CCNA Guide to Cisco Networking

  26. ISDN Operations (continued) • Functions and references (continued) • Reference points • U: Demarc between client and telco • R: Point between non-ISDN equipment (TE2) and TA • S: Point between customer’s TE1 or TA and the network termination (NT1 or NT2) • T: Point between a NT1 and a NT2 • S/T: Point between TA and NT1 in the absence of a NT2 CCNA Guide to Cisco Networking

  27. SPID • Connect to service provider switch • Service Profile Identifier (SPIDs) • Dial-in access • ISDN phone numbers • Provide a profile • Service level agreement • AutoSPID CCNA Guide to Cisco Networking

  28. SPID (continued) • Service provider switch types • dms-100: Northern Telecom DMS-100 (as previously described) • ni1: National ISDN-1; used in North America • net3: Net3 switch; used in Europe and the United Kingdom • ntt: Switch from NTT; used in Japan • 1tr6: 1TR6 switch; used in Germany • ts013:TS013 Australian switch • none: Used when a switch has not been specified CCNA Guide to Cisco Networking

  29. SPID (continued) CCNA Guide to Cisco Networking

  30. Multilink PPP • Combine the bandwidth of individual links or channels • Multilink provides • Load balancing • Packet fragmentation and reassembly • Sequencing for packets • Creates one logical connection • Function over synchronous or asynchronous connections • Router(config-if)# ppp multilink CCNA Guide to Cisco Networking

  31. DDR • Dial-on-demand routing (DDR) • Intermittent WAN access • Saves money on metered lines • Used with circuit switched access • Define interesting traffic • Common configuration commands • “dialer-list” command • “dialer-group” command • “access-list” command CCNA Guide to Cisco Networking

  32. DDR (continued) CCNA Guide to Cisco Networking

  33. DDR (continued) CCNA Guide to Cisco Networking

  34. ISDN BRI Configuration Examples CCNA Guide to Cisco Networking

  35. ISDN BRI Configuration Examples (continued) • Dialer profiles • Scalable compared to legacy DDR • Configuration of dialer profiles involves • Dialer interface • Logical configuration • Dial string for each destination subnet • Dialer map class • Optional commands • Define characteristics for each call • Dialer pool • Identify the physical interface that will be used by the dialer interface CCNA Guide to Cisco Networking

  36. ISDN BRI Configuration Examples (continued) CCNA Guide to Cisco Networking

  37. Monitoring ISDN • ISDN problems are often associated with • PPP configuration • “debug ppp authentication” • “debug ppp negotiation” • “clear interface” • Dialer configurations • “show dialer” • “show interface” • “debug dialer” • ISDN monitoring commands • “show isdn status” • “show interface bri 0” • “debug q921” CCNA Guide to Cisco Networking

  38. Digital Lines • T1: 24-channel, 1.544 mbps • T1C: 48-channel, 3.152 mbps • T2: 96-channel, 6.312 mbps • T3: 672-channel, 44.376 mbps • T4: 4032-channel, 274.176 mbps • E1: 30-channel, 2.048 mbps • Fractional T1 or E1 • Digital Subscriber Line (DSL) CCNA Guide to Cisco Networking

  39. Summary • Many WAN connectivity options are available for modern networks, including digital lines, Frame Relay, and analog modems • WAN technologies typically define Data Link and Physical layer standards • The Point-to-Point Protocol (PPP) is the most widely used WAN protocol today • On Cisco routers, PPP is used mainly as a Data Link layer encapsulation method; however, it does provide an interface to the Network layer via specific Network Control Protocols (NCPs) CCNA Guide to Cisco Networking

  40. Summary (continued) • PPP provides link establishment, quality determination, Network layer protocol encapsulation, and link termination services • PPP is often used over Integrated Services Digital Network (ISDN) connections • ISDN is a digital service provided by several telecommunications companies worldwide • ISDN was developed as a faster WAN connection to replace analog modems, and as a cheaper alternative to Frame Relay and full T1 connections • ISDN service comes in Basic Rate Interface (BRI) and Primary Rate Interface (PRI) CCNA Guide to Cisco Networking

  41. Summary (continued) • BRI offers connections of up to 128 Kbps for data transfer, and PRI offers up to 24 channels in the United States, each with the ability to transfer data at 64 Kbps • Connections over ISDN can take advantage of dial-on-demand routing (DDR) and multilink services offered through PPP connections • DDR allows the router using an ISDN connection to dial only when there is interesting traffic and to add more channels as needed to support given traffic levels • DDR can be implemented using dialer profiles, which allow more flexibility regarding the calling parameters • Multilink allows ISDN to use multiple channels evenly by spreading the load across those channels CCNA Guide to Cisco Networking

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