Cisco S4C5 ISDN

Designed to solve low bandwidth problems in small offices Also designed for dial-in users with traditional telephone dial-in services Designed to use existing telephone wiring WAN length brought up for duration of call Sane process as when you call a friend

Benefits Carries many types of network traffic (data, voice, video) Sets up calls faster than basic telephone service Faster data transfer rate than modems –Uses D channel (out of band) signaling –B channel 64 Kbps up to 128 when both B channels are used Uses UNI (user-network interface) International compatibility –Standards for end-to-end digital connectivity

ISDN Components TE1connects to network termination of type 1 or 2 –device compatible with ISDN TE2device that is not compatible– requires terminal adapter TAConverts standard electrical signals to ISDN form NT1Connects four-wire ISDN subscriber wiring to conventional two-wire local loop NT2performs layer 2 and layer 3 protocol services

ISDN Reference Points Rconnections between non ISDN and a TA Sconnections to customer switching device Toutbound connection from NT2 to ISDN or NT1 Uconnections NT1 and ISDN owned by telephone company – only in NA

Switch Types North America –AT&T 5ESS Nortel DMA-100 Japan NTT UK Net3 Net5

ISDN Protocols Erecommend telephone network standards; e.g. E.164 international addressing Iconcepts, terminology and methods; e.g. I.100 concepts and structure Qswitching and signaling; signaling means process of call setup

Layers Physical –ISDN BRI and PRI Data Link –LAPD; LAPB Network Layer –Q.930 – user to user, circuit switched, and packet switched connections

Physical Layer 48 bits or 24 bits plus 24 bits –Framing – synchronization –Load Balancing –Echo of previous D channel bits –Activation bit –Spare bit –B1 channel bits –B2 channel bits –D channel bits 8000 frames per second; effective rate is 144 Kbps

Data Link Layer Flag, address, control, data, FCS, flag Address – SAPI C/R EA TEI EA LAPD – similar to HDLC –Used to ensure control and signaling information flows and is received properly –Flag and control fields identical to HDLC –The address field can be expanded to 2 bytes

Network Layer ITU-T ITU-TQ.931 –Support user to user, circuit switched and packet switched connections –Specifies call establishment, termination, information, and miscellaneous messages

ISDN and OSI Reference Model Two most common encapsulations –PPP and HDLC –ISDN defaults to HDLC –PPP is more robust – authentication and negotiation of compatible link and protocol configuration ISDN allows only one encapsulation type –Most use PPP – peer to peer –Can be used by IP and IPX to establish network connectivity –PPP specified by RFC 1661 – open standard –PPP uses LCP to establish link

PPP Security PAPPassword Authentication Protocol CHAPChallenge Handshake Authentication Protocol –If syn used on one end, asyn used on other –LCP established Point to point –PPP provides primary security – RFC 1334 –CHAP is bidirectional –PAP is unidirectional

ISDN Uses Remote access –Lowest speed link in enterprise Remote nodes –Remote user appears to be network node –Components are ISDN router and remote client sw Small office/home office –ISDN router with multiple users - dialup –Fees depend on geographic area, service availability, and billing method –May be distance limitations

ISDN Services BRI –2 B and 1 D channel, 144 kbps total bandwidth –B channels provide service; D channel used for signaling PRI –23 B 8-bit channels and 1 8-bit D channel –1.544 Mbps –In Europe, 30 8-bit channels and 1 D

How It Works Routers provide routing by using DDR (dial on demand) routing to provide transparent connectivity DDR controls B channels based on load thresholds Multilink PPP is used to provide bandwidth aggregation

Configuration Tasks Global –Select switch type, specify traffic to trigger DDR call Set destination details Interface Configuration –Select interface specs, configure ISDN addressing Specify BRI and number for BRI port Configure with ID supplies by service provider Can configure waiting time for carrier to respond Involves ISDN, switch type, and ISDN SPIDs

BRI Configuration INTERFACE BRI 0 –Number describes port, connector, or interface card number –Displayed with SHOW INTERFACES command

Switch Types Need to define ISDN Switch type before using BRI Use global configuration mode –ISDN Switch-type name-of-switch-type

SPIDS ISDN spid1 spid-number [idn] seta a B channel service profile identifier –SPIDs allow multiple ISDN devices to share local loop –Typically used for dialup connectivity

Typical Commands Isdn switch-type Dialer-list 1 protocol ip permit Interface bri 0 Dialer-group 1 Dialer wait-for-carrier-time Ip Bane Connection number Show ISDN status

DDR Operations Ping/Telnet Show dialer – diagnostics Show ISDN Active – monitor call in progress Show ISDN status – shows statistics of all line connections Debug isdn q921 Debug dialer Clear interface