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CCNA 4 v3.0 Module 4 ISDN and DDR

CCNA 4 v3.0 Module 4 ISDN and DDR. Cisco Networking Academy. Objectives. ISDN concepts ISDN configuration DDR configuration. Integrated Services Digital Network.

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CCNA 4 v3.0 Module 4 ISDN and DDR

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  1. CCNA 4 v3.0 Module 4ISDN and DDR Cisco Networking Academy

  2. Objectives • ISDN concepts • ISDN configuration • DDR configuration

  3. Integrated Services Digital Network • ISDN allows multiple digital channels to operate simultaneously through the same regular phone wiring used for analog calls, but ISDN transmits a digital signal rather than analog. • ISDN uses the Public switched telephone networks (PSTNs) to accomplish this.

  4. Digital Communication with ISDN • Telephone companies developed ISDN with • the intention of creating a totally digital network. • ISDN became possible when the telephone company • switches were upgraded to handle digital signals.

  5. Traditional PSTN vs. ISDN • The traditional PSTN was based on an analog connection between the customer premises and the local exchange, also called the local loop. • The analog circuits introduce limitations on the bandwidth. • Circuit restrictions do not permit analog bandwidths greater than approximately 3000 Hz. • ISDN technology permits the use of digital data on the local loop, providing better access speeds for the remote users.

  6. ISDN Benefits • ISDN is a set of standards that define an end-to-end digital network. • ISDN Benefits are: • Carries many types of network traffic (voice, data, multimedia). • Sets up calls faster than basic telephone because call setup is out-of-band on the D channel • Faster data transfer rates on the B channels (64 kbps) with an aggregate bandwidth of 128 kbps.

  7. ISDN Standards (process of establishing an ISDN call) ISDN standards are set by the ITU-T

  8. ISDN Access Options 2B+D 23B+D

  9. ISDN 3-Layer Model

  10. Layer 1 • ISDN physical layer, or Layer 1, frame formats differ depending on whether the frame is outbound or inbound. • If the frame is outbound, it is sent from the terminal to the network. • Outbound frames use the TE frame format. • If the frame is inbound, it is sent from the network to the terminal. • Inbound frames use the NT frame format. • http://www2.rad.com/networks/1994/isdn/isdnarch.htm

  11. Layer 2 • Each frame contains two sample frames each containing the following: • 8 bits from the B1 channel • 8 bits from the B2 channel • 4 bits from the D channel • 6 bits of overhead • ISDN BRI frames contain 48 bits. Four thousand of these frames are transmitted every second. • The physical bit rate for the BRI interface is 48*4000 = 192 kbps. • The physical bit rate takes the 6 bits of overhead into account • The effective rate is 144 kbps = 64 kbps + 64 kbps + 16 kbps (2B+D). • Layer 2 of the ISDN signaling channel is LAPD, which is similar to HDLC.

  12. Layer 3 • The Delta - “D” channel is used for call control functions such as call setup, signaling, and termination. • These functions are implemented in the Q.931 protocol. • Since ISDN switches were developed before Q.931 was standardized, the various ISDN providers and switch types use various implementations of Q.931. • For this reason routers must have commands in their configuration specifying the ISDN switch to which they are connecting.

  13. Call Processing • The D channel is used to send the called number to the local ISDN switch. • The local switch uses the SS7 signaling protocol to set up a path and pass the called number to the remote ISDN switch. • The remote ISDN switch signals the destination over the D channel. • The destination ISDN NT-1 device sends the remote ISDN switch a call-connect message. • The remote ISDN switch uses SS7 to send a call-connect message to the local switch. • The local ISDN switch connects one B channel end-to-end, leaving the other B channel available for a new conversation or data transfer. Both B channels can be used simultaneously.

  14. Q.931 Messaging-Call Setup Example Q.931 1 D Q.931 3 D 2 SS7 5 SS7 4 D 6 B

  15. ISDN Functions and Reference Points

  16. ISDN Functions and Reference Points Vendors can create hardware that supports one or more functions.

  17. BRI Reference Points • ISDN specifications define four reference points that connect one ISDN device to another. R — References the connection between a non-ISDN compatible device Terminal Equipment type 2 (TE2) and a Terminal Adapter (TA), for example an RS-232 serial interface. S — References the points that connect into the customer switching device Network Termination type 2 (NT2) and enables calls between the various types of customer premise equipment. T — Electrically identical to the S interface, it references the outbound connection from the NT2 to the ISDN network or Network Termination type 1 (NT1). U — References the connection between the NT1 and the ISDN network owned by the telephone company

  18. BRI Reference Points

  19. Cisco ISDN BRI Interfaces

  20. S/T ISDN Interface ISDN Interfaces 1B-U ISDN Interface NOT PRI

  21. BRI interfaces • To select a Cisco router with the appropriate ISDN interface, do the following: • Determine whether the router supports ISDN BRI. Look on the back of the router for a BRI connector or a BRI WAN Interface Card (WIC). • Determine the provider of the NT1. An NT1 terminates the local loop to the central office (CO) of the ISDN service provider. In the United States, the NT1 is Customer Premise Equipment (CPE), meaning that it is the responsibility of the customer (Basically, you must provide your BRI interface). In Europe, the service provider typically supplies the NT1. • If the NT1 is built into the CPE, the router should have a U interface. If the router has an S/T interface, then it will need an external NT1 to connect to the ISDN provider.

  22. ISDN Switch Types

  23. Configuring ISDN BRI

  24. Configuring ISDN BRI

  25. Service Profile Identifiers (SPID) • A SPID is a number provided by the ISDN carrier to identify the line configuration of the BRI service. • SPIDs are assigned by the telco. • Each SPID points to line setup and configuration information. • SPIDs are a series of characters that usually resemble telephone numbers. • SPIDs identify each B channel to the switch at the central office.

  26. ISDN PRI • ISDN PRI is delivered over a leased T1 or E1 line. • The main PRI configuration tasks are: • 1. Specify the correct PRI switch type that the router interfaces with at the CO of the ISDN provider. • 2. Specify the T1/E1 controller, framing type, and line coding for the facility of the ISDN provider. 3. Set a PRI group timeslot for the T1/E1 facility and indicate the speed used.

  27. Verifying ISDN Configuration

  28. Troubleshooting ISDN Configuration

  29. Dial on Demand Routing (DDR) • DDR defines the process of a router connecting to the ISDN network using dialup when there is “interesting” traffic to send, and then disconnecting when the transfer is complete or idle. • Interesting traffic is designated by the dialer-list • DDR is used when a constant connection is not needed, thus reducing costs.

  30. DDR Operation As additional interesting traffic crosses the interface the idle-timeout is reset.

  31. DDR Operation No Yes

  32. Configuring Legacy DDR

  33. Static Route Configuration

  34. Defining Static Routes and Dynamic Routes • When configuring routing, consider that the BRI interface will become active and remain active as interesting traffic crosses the interface. • If interesting traffic is loosely defined, ‘protocol ip permit’, then routing updates will also cause the interface to become or remain active. • One solution is to not include the BRI interface as one of the network statements and instead use static routes. • or • Configure the BRI interface as a passive interface as part of the routing protocol configuration.

  35. Specifying Interesting Traffic The dialer list is applied to the BRI interface by using the ‘dialer-group’ command.

  36. The dialer-group Command

  37. Configuring the DDR Dialer Interface (Legacy) • There are several steps involved in configuring the DDR dialer information. • Configure the encapsulation type (PPP, HDLC). • If the encapsulation type is PPP then configure authentication if needed. • Configure a dialer map to associate a destination IP address with the correct dialer string (phone #). • Configure an idle-timeout.

  38. Configuring Dialer Information - PPP

  39. The dialer-map Command ‘broadcast’

  40. The dialer idle-timeout Command

  41. Dialer Profiles (non legacy DDR) • Legacy DDR is limited because the configuration is applied directly to a physical interface. • Dialer profiles remove the configuration from the interface and only bind the configuration to the interface on a per-call basis. • Dialer profiles allow physical interfaces to dynamically take on different characteristics based on incoming or outgoing call requirements.

  42. Dialer Profiles • Dialer profiles separate the logical portion of DDR (network layer, encapsulation and dialer parameters) from the physical interface that places or receives calls. • A dialer profile consists of the following elements: • Dialer interface – logical interface • Dialer pool – group of physical interfaces • Physical interfaces – physical interfaces are ‘dialer pool-members’

  43. ‘dialer pool 0’ Physical interfaces can belong to multiple dialer pools but dialer interfaces can only belong to one dialer pool only. ‘dialer pool-member 0’ Dialer pool 1 ‘dialer pool-member 1’ Dialer Profile Elements

  44. Configuring Dialer Interfaces Note the IP addresses, the ‘dialer-group’ and the encap are on the dialer interfaces

  45. Configuring Dialer Interfaces RouterA(config)# interface BRI0 RouterA(config-if)# encapsulation ppp RouterA(config-if)# dialer pool-member 1 RouterA(config-if)# dialer pool-member 2 RouterA(config-if)# ppp authentication chap RouterA(config-if)# ppp multilink RouterA(config-if)# interface Dialer 1 RouterA(config-if)# ip address 192.168.1.1 255.255.255.252 RouterA(config-if)# encapsulation ppp RouterA(config-if)# dialer remote-name RouterB RouterA(config-if)# dialer string 5105551234 RouterA(config-if)# dialer load threshold 50 RouterA(config-if)# dialer pool 1 RouterA(config-if)# dialer-group 1

  46. Verifying DDR • show dialer • show dialer interface [BRI] • show isdn active • show isdn status

  47. Troubleshooting DDR • debug isdn q921 • debug isdn q931 • debug dialer [events|packets] • isdn call interface • clear interface bri

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