Semester 6 – Chapter 4

1. Semester 6 – Chapter 4 ISDN

2. ISDN Uses • Used primarily as a WAN backup technology • to provide remote access to telecommuters and small offices • to support large numbers of POTS (analog modem) and/or ISDN Basic Rate Interface (BRI) calls.

3. DSL vs ISDN • offers much higher throughput at a lower cost. • However, ISDN still used because • ISDN is more widely available than DSL or cable. • Many companies and service providers have made a significant investment in ISDN equipment and training, and plan to continue leveraging that investment. • Remote offices using ISDN can connect to central offices directly, without traversing the public Internet. Most DSL and cable implementations require the remote host communicate with the central site using a VPN over the Internet.

4. ISDN Advantages Over Analog (Asychronous) • Higher Speed • Faster Call Setup • Cheaper than leased lines • Can run voice and data simultaneously

5. BRI Characteristics • Two 64-kbps bearer channels • One 16-kbps delta channel • 48 kbps of framing and synchronization information • Total speed of 192 kbps • Although not commonly done, you may reference the total bandwidth of an ISDN BRI, including framing and synchronization, which is 192 kbps.

6. PRI over T1 • 23 64-kbps bearer channels • One 64-kbps D channel, carried in timeslot 24 • 8 kbps of framing and synchronization information • Total speed of 1.544 Mbps

7. PRI Over E1 • 30 64-kbps bearer channels • One 64-kbps D channel, carried in timeslot 16 • 64 kbps of framing and synchronization information • Total speed of 2.048 Mbps

8. ISDN Call Processing • Signaling System 7 (SS7) protocols used to set up a path inside the public switched telephone network (PSTN) • 931.q is used between end user and ISDN switch • D channel is used for signaling

9. Designations • E Telephone network standards • I Concepts, terminology, and methods • Q Signaling and switching

10. PRI • a channel service unit/data service unit (CSU/DSU) is required to connect a router (the TE) to the carrier network. Internal CSU/DSUs are common among modular routers. • PRI's primary application is modem aggregation – not point-to-point connectivity • Can provide both analog and digital dial solutions

11. ISDN and OSI Model • Operates at layers 1 2, and 3 • Layer 1 • .430 for BRI, .431 For PRI, ANSI T1.601 for BRI • Layer 2 • As specified by Q.921, the D channel typically frames data using Link Access Protocol on the D channel (LAPD) • Layer 3 • the B channel can carry datagrams using a variety of Layer 3 protocols, including IP, IPX, and AppleTalk.

12. TE1 Addresses • 0-63 for non-automatic TEI assignment • 64-126 for automatic TEI assignment • 127 for group assignment, or broadcast • TEI works together with the service access point identifier (SAPI) to complete the Layer 2 address • SAPI is a 6-bit number used to identify and manage • TEI represents the specific ISDN device, while the SAPI represents the specific process running on that device

13. ISDN Call Termination • disconnect • release • release complete • It issues a disconnect message to the calling party. • It starts a timer to ensure receipt of a released message. • It disconnects the switched path. • When a released message is received from the preceding exchange, it returns a release complete message to the preceding exchange.

14. ISDN Addressing Tasks • Assign the IP address • Assign dialer group (for DDR), • Assign ISDN service profile statements (SPID numbers • Include a dialer map command that associates a statically mapped destination to a destination IP address, hostname, and ISDN dial number. • ISDN switch type can be set in global mode or assigned to individual interfaces

15. BRI Interface Commands • RTA(config)#interface bri 0RTA(config-if)#isdn switch-type basic-5ess • Router(config-if)#encapsulation ppp • Router(config-if)#ppp authentication chap • Other encapsulations • encapsulation [ppp | labp | hdlc | x25 | cpp]

16. DDR Configuration • 1.Define what constitutes interesting traffic by using the dialer-list command. • 2.Assign this traffic definition to an interface by • using the dialer-group command. • 3.Define the destination address, hostname, and • telephone number to dial by using the dialer • map command. • 4.(Optional) Define call parameters by using other • dialer commands such as dialer idle-timeout, dialer fast-idle, and dialer load-threshold.

17. Dial-on-Demand Commands • Router(config)#dialer-list dialer-group-number protocol protocol-name {permit | deny} • RTA(config)#dialer-list 1 • Router(config)#access-list access-list-number [permit |deny] {protocol | protocol- keyword}{source source-wildcard | any}{destination destination-wildcard | any}[protocol-specific-options] [log]protocol ip permit

18. Attach Dialer List to Interface • Router(config)#dialer-list 1 protocol ip permit • Router(config)#interface bri0 • Router(config-if)#dialer-group 1 • Note: For a given protocol and a given dialer group, only one access-list can be specified in the dialer-list command.

19. Dialer Map Command • Identifies destination router information, such as the phone number to dial: • Router(config-if)#dialer map protocol next-hop-address [name hostname] [broadcast] dial-string • Cisco IOS commands often contain the word "map," which is used to statically map Layer 2 addresses to Layer 3 addresses • Dialer maps for inbound calls are maps between protocol addresses and authenticated user names

20. Call Parameters • Router(config-if)#dialer idle-timeout seconds • Router(config-if)#dialer fast-idle seconds • Router(config-if)#dialer load-threshold load [outbound | inbound | • To manually set the idle timeout value, use the dialer idle-timeout command • By default, the idle-timeout is set to 120 seconds either] • The dialer load-threshold command is used to specify the interface load at which the router will initiate another call to the destination

21. DDR Environment • In a DDR environment, dynamic routing can be a source of problems. • Routing protocols such as RIP and OSPF rely on regular communication between link partners. • If routers are connected via a dial-up link, active connections are usually intermittent.

22. Routing Solutions • WAN core and remote sites run different protocols, route redistribution may be necessary to "share" routing information between the different protocols. • use static and default routing to address the challenge of routing in a DDR network • use dynamic routing, including route redistribution, to propagate routes • Use snapshot routing for serial connections

23. Static routes are entered manually – no need for routing tables • Central(config)#ip route 172.24.2.0 255.255.255.010.2.3.2 • At least one static route pointing to the next-hop IP address is necessary for DDR to work • Router(config)#ip route 0.0.0.0 0.0.0.0 {next-hop-address | exit-interface}

24. Redistributing EIGRP/Static • RTA(config)#ip route 123.22.1.1 255.255.255.0 bri0 • RTA(config)#router eigrp 100 • RTA (config-router)# redistribute static

25. Passive Interface • R(config)#IP route 10.0.0.1 255.255.0.0 192.16.3.0 • R(config)#router rip • R(config)#version 2 • R(config)#network 10.0.0.0 • R(config)#redistribute static • R(config)#passive-interface bri0/0 • To avoid routing updates initiating a call

26. Snapshot Routing • RIP for IP, IGRP for IP, Novell RIP and SAP for Novell IPX, Routing Table Maintenance Protocol (RTMP) for AppleTalk, Routing Table Protocol (RTP) for Banyan VINES • When distance vector router updates are not considered interesting traffic, router drops call and route will drop from table • The hellos from OSPF will keep initiating calls • Redistribute routes and using RIP between serial connections

27. Snapshot Routing • Uses the client-server design model • one router is designated as the snapshot server and one or more routers are designated as snapshot clients • At the end of the active period, the router takes a snapshot of the entries in its routing table. These entries remain frozen during what is called the quiet period • client router determines the frequency at which it calls the server router. The quiet period can be as long as 100,000 minutes (over 69 days)

28. Snapshot Commands • Router(config-if)#snapshot server active-time [dialer] • Router(config-if)#snapshot client active-time quiet-time [suppress-statechange-updates] [dialer] • Router(config-if)#dialer map snapshot sequence-number dial-string • The value of the active-time argument must be the same for the client and server routers • make sure your active time is long enough to allow any routing updates to be sent

29. Suppress-Statechange • suppress-statechange-update option disables the exchange of routing updates each time the line protocol goes from "down" to "up"or from "dialer spoofing" to "fully up. • The dialer map snapshot command specifies which router to call as the snapshot server.spoofing" to "fully up.

30. Aggregation • Cisco Proprietary BOD • triggered by outgoing traffic levels only • load value is a number from 1 to 255 • 1 IS 0%; 255 IS 100% • Multilink PPP (MLP) • Triggers by outgoing or incoming traffic • Both of these methods require the dialer load-threshold command • Router(config-if)#dialer load-threshold [inbound | outbound | either ] • only one end of a link should be configured with the dialer load-threshold command.

31. Use PPP Multilink • Asynchronous serial interfaces in dialer rotary groups • Synchronous serial BRI • Multiple BRIs in dialer rotary groups • Multiple BRIs using dialer profiles • PRI B channels in dialer rotary groups

32. Accepting Calls • You can ensure that only a single device answers an incoming call by verifying the number or subaddress in the incoming call against the device configured number, subaddress, or both. • ISDN routers can be configured to screen incoming calls by using calling line identification (CLID) • Router(config-if)#isdn caller phone-number

33. ISDN Rate Adaptation • Router(config-if)#dialer map protocol next-hop-address [name name] [speed speed] [broadcast] dial-string • Assigned on per destination basis • Lower speed is accepted

34. Debugging Commands • Show ip int bri0/0 • Show ip int brief • Show isdn status • Show isdn history • Show dialer • Show ppp multilink • Debug dialer • Debug ppp multilink • Debug isdn events • Debug ppp authentication | negotiation

35. D Channel Debugging • debug isdn q921 at Layer 2 • debug isdn q931 at Layer 3. • display information about call setup and teardown of ISDN network connections at Layer 3 on the D channel. • includes a call setup message, indicated by "SETUP" in the first line. • In the second line, the Bearer Capability value of 0x8890 indicates that the coding standard used is ITU-T and the circuit mode is 64kbps.

36. PRI Configuration • .Specify the correct PRI switch type that the router interfaces with at the provider's Central Office (CO). • Specify the T1/E1 controller, framing type, and line coding for the provider's facility. • Set a PRI group timeslot for the T1/E1 facility and indicate the speed used. • Identify the interface that you will configure to act with DDR.

37. T1/E1 Configuration • Router(config)#controller {t1 | e1}{slot/port | unit number} • Router(config)#controller t1 • Router(config-controller)#framing {sf | esf} • Router(config-controller)#framing{crc4 | no-crc4} [australia] • Router(config)#controller e1 • Router(config-controller)#framing crc4 • Router(config-controller)#linecode hdb3