Transcript Cisco S4C5
Cisco S4C5 ISDN 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 • TE1 connects to network termination of type 1 or 2 –device compatible with ISDN • TE2 device that is not compatible– requires terminal adapter • TA Converts standard electrical signals to ISDN form • NT1 Connects four-wire ISDN subscriber wiring to conventional two-wire local loop • NT2 performs layer 2 and layer 3 protocol services ISDN Reference Points • R connections between non ISDN and a TA • S connections to customer switching device • T outbound connection from NT2 to ISDN or NT1 • U connections 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 • E recommend telephone network standards; e.g. E.164 international addressing • I concepts, terminology and methods; e.g. I.100 concepts and structure • Q switching 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.1.450 • 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 • PAP Password Authentication Protocol • CHAP Challenge 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