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.High-performance routing provides critical functionality in the high-speed WANenvironment.The Cisco 7500 router series extends the capabilities of the Cisco 7000 family and incorporates distributed switchingfunctions.The distributed switching capability allows network designers to provide the high-performance routing necessary tosupport networks using ATM, multilayer LAN switching, and VLAN technologies.The Cisco 7500 family of routers offers a broad support of high-speed ATM and WAN interfaces.The higher port densitiessupported the Cisco 7500 series easily handles the large number of interfaces that result from more remote site connectivity.The Cisco IOS software adaptive rerouting increases network availability, and its flexible interfaces provide support formultiple services and a migration path to ATM.Network designers can deploy the Cisco 7500 series in the WAN environmentto access multiple types of carrier service offerings as they migrate from TDM backbones to ATM backbones.The Cisco 7500series also provides network security and minimizes the loss of transparency.The Cisco 7500 series running Cisco IOSSoftware Release 11.0 or later provides tools for network configuration, fault detection, and minimizing unnecessary trafficacross expensive wide-area links.http://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2008.htm (32 of 38) [9/16/2000 5:09:34 PM] Designing ATM InternetworksNote The features discussed for the Cisco 7000 series are also applicable to the Cisco 7500 series.Cisco 7000 SeriesWith a CxBus card, the AIP can be installed in a Cisco 7000 and Cisco 7500 series routers and is compatible with all theinterface processors as well as the Route Processor (RP), the Switch Processor (SP), the Silicon Switch Processor (SSP), andthe new Route Switch Processor (RSP).The AIP supports the following features:Single, native ATM port with transmission rates up to 155 Mbps over a variety of ATM physical layer interface mediamodules (PLIM), eliminating the need for an external ATM data service unit (DSU).Multiprotocol support over ATM for all the popular network operating systems and the internet protocol: IP, AppleTalk,Novell IPX, DECnet, Banyan VINES, XNS, and OSI CLNS.ATM Adaptation Layers (AALs) 3/4 and 5.Dual RISC and dual-SAR design for high-speed cell and packet processing.Interim Local Management Interface (ILMI) for ATM address acquisition/registration.Note Cisco IOS Software Release 10.0 supports AAL5 PVCs only.Cisco IOS Software Release 10.0 and later support ATM Forum UNI Specification V3.0, which includes the user-to-networkATM signaling specification.The AIP card uses RFC 1483 (Multiprotocol Encapsulation over AAL5) to transport datathrough an ATM network.RFC 1483 specifies the use of an LLC/SNAP 8-byte header to identify the encapsulated protocol.Italso specifies a null encapsulation (VC Mux) which, instead of headers, creates a separate virtual circuit per protocol.The following physical layer interface modules (PLIMs) are available for the AIP:TAXI 4B/5B 100-megabits-per-second (Mbps) multimode fiber-optic cableSONET/SDH 155-Mbps multimode fiber-optic (STS-3c or STM1) cableSONET/SDH 155-Mbps single mode fiber-optic (STS-3c or STM1) cableE3 34-Mbps coaxial cableDS-3 45-Mbps cableThe total bandwidth through all the AIPs configured in a router should be limited to 200 Mbps full duplex.For that reason,only the following combinations are supported:Two TAXI interfacesOne SONET and one E3 interfaceTwo SONET interfaces, one of which is lightly usedFive E3 interfacesThe AIP includes hardware support for various traffic-shaping functions.Virtual circuits can be assigned to one of eight ratequeues, each of which is programmable for a different peak rate.Each virtual circuit can be assigned an average rate andspecific burst size.The signaling request specifies the size of the burst that is sent at the peak rate, and after that burst, the restof the data is sent at the average rate.The following are the configurable traffic parameters on the AIP:Forward peak cell rateBackward peak cell rateForward sustainable cell rateBackward sustainable cell rateForward maximum burstBackward maximum burstFigure 8-22 shows how the routing table and address resolution table on Router A are used to forward data to a workstationbehind Router C.http://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2008.htm (33 of 38) [9/16/2000 5:09:34 PM] Designing ATM InternetworksFigure 8-22: AIP connects LANs to ATM fabric.The routing table on Router A performs its usual function of determining the next hop by mapping the network number of thedestination (in this case 144.254.45 from the incoming packet) to the IP address of the router to which the destination networkis connected (in this case, 144.254.10.3, which is the IP address of Router C).An address resolution table maps the next-hop IPaddress to an ATM NSAP address (in this case, represented by ¼).Router A signals Router C over the ATM network toestablish a virtual connection, and Router A uses that connection to forward the packet to Router C.Figure 8-23 shows thelayers through which the packet travels.Figure 8-23: Path of an IP packet over the ATM fabric.Configuring the AIP for ATM SignalingThe following commands configure an AIP for ATM signaling:interface atm 4/0ip address 128.24.2.1 255.255.255.0no keepaliveatm nsap-address AB.CDEF.01.234567.890A.BCDE.F012.3456.7890.1234.12atm pvc 1 0 5 qsaalmap-group shastaatm rate-queue 0 155atm rate-queue 1 45map-list shastaip 144.222.0 atm-nsap BB.CDEF.01.234567.890A.BCDE.F012.3456.7890.1234.12ip 144.3.1.2 atm-nsap BB.CDEF.01.234567.890A.BCDE.F012.3456.7890.1234.12 classQOSclasshttp://www.cisco.com/cpress/cc/td/cpress/ccie/ndcs798/nd2008
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