CCNA Guide to Cisco Networking

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

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

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)

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)

6. PPP In The Protocol Stack (continued)

7. Frame Format

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

9. Frame Format (continued) Frame fields of PPP (continued) LCP or Data: 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

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

11. LCP Link Configuration LCP link configuration process includes Link establishment Authentication (optional) Link-quality determination (optional) Network layer protocol configuration negotiation Link termination

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

13. Establishing PPP Communications (continued)

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

15. Configuring PPP Authentication (continued)

16. Configuring PPP Authentication (continued)

17. Configuring PPP Authentication (continued)

18. Confirming PPP Communications “show interface” command Router# show interface serial 0/0

19. ISDN Circuit-switched service Existing telephone service Data Voice Video Audio transmission Faster than traditional modem speeds

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

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

22. ISDN (continued)

23. ISDN Standards

24. ISDN Operations

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)

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

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

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

29. SPID (continued)

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

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

32. DDR (continued)

33. DDR (continued)

34. ISDN BRI Configuration Examples

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

36. ISDN BRI Configuration Examples (continued)

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”

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)

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)

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)

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