IBM SC30-3681-08 manual ATM-LLC Multiplexing, ATM Virtual Interface Concepts

Con®guring ATM and LAN Emulation

This information applies to addresses entered for ATM; LAN emulation;

Classical IP and ARP over ATM; and IPX and ARP over ATM.

ATM-LLC Multiplexing

Protocols that run natively over an ATM interface can use ATM-LLC multiplexing to share ATM addresses and both SVC and PVC channels between users. ATM-LLC

is implicitly con®gured when the protocols are con®gured and can be monitored using the ATM Config+ command prompt from t 5. There are no explicit

con®guration options for the ATM-LLC multiplexing function. For example, if two protocols which use ATM-LLC multiplexing are con®gured to use the same local ATM address (local endpoint), this implicitly con®gures ATM-LLC to use the same shared ATM address for both protocols.

See ªATM-LLC Monitoring Commandsº on page 290 for additional information.

Sharing of ATM addresses or SVC/PVC channels is not possible between protocols that use the ATM-LLC multiplexing function and those that do not use the ATM-LLC multiplexing function (such as Classical IP). Currently, Server Cache Synchronization Protocol (SCSP) and APPN are the only two protocols that use the ATM-LLC multiplexing function.

ATM Virtual Interface Concepts

An ATM Virtual Interface (AVI) creates the appearance of multiple ATM interfaces when, in fact, there is only one physical ATM interface. One or more AVIs can be con®gured for each physical ATM interface on the router. AVIs have the following characteristics:

vEach AVI must be de®ned on one (and only one) physical ATM interface. ATM real interface (ARI) will be used to mean a physical ATM interface.

vOne or more AVIs can be con®gured on each ARI on a router.

vHigher layer protocols treat ARIs and AVIs equally. The protocols see the total number of ATM interfaces as the sum of the number of ARIs and AVIs con®gured on the router.

vProtocols can be con®gured on each ATM interface (real or virtual) independently of other interfaces.

For example, one can con®gure IP on interface 0 (which is a real ATM interface) with IP address 9.1.1.1 and another instance of IP with address 9.2.1.1 on interface 1 (which is an AVI). Whether an interface is a real ATM interface or a virtual interface con®gured on a real interface makes no difference to the protocol (IP in the example). In addition, whether virtual interface 1 is con®gured on top of real ATM interface 0 or some other physical ATM interface is also transparent to the protocols.

Advantages of Using ATM Virtual Interfaces

Major advantages of using the ATM Virtual Interfaces are:

vUsing the ATM Virtual Interface feature increases the number of protocol instances that can be supported on a physical ATM interface.

The actual number of AVIs that can be con®gured on an ARI is limited by physical resources, such as memory, available on the router. The total number of

274MRS V3.2 Software User's Guide