Nortel Networks 8672ATME manual Physical description, RFC 1483 Support

28Chapter 1 About the Passport 8672ATME Module

The VBR service provided by the 8672 module allows a previously idle channel to burst at a relatively high Peak Cell Rate (PCR) for a Maximum Burst Size (MBS) of ATM cells. If the channel exhausts its MBS, the module reduces the channel’s rate to a Sustained Cell Rate (SCR). When the channel stops transmitting, it accumulates credit towards another burst at PCR.

The 8672 module also provides a UBR service for Transmitter channels. When a UBR channel is opened, there is no channel rate specified. All active UBR channels are serviced in a round-robin queue. If no rate-shaped channel is scheduled for transmission, a single cell is sent from the channel at the head of the UBR queue.

RFC 1483 Support

The system software on the Passport 8672ATME Module supports the configuration of RFC 1483 LAN clients with multiprotocol encapsulation. RFC 1483 supports standards-based methods of encapsulation that enable connectivity with third-party ATM devices. Multiprotocol encapsulation provides the capability to set up PVCs between Centillion ATM virtual ports (VPorts) and other clients based on LLC encapsulation. The current Centillion platform only supports bridged variations of RFC 1483.

The Passport 8672ATME Module supports the following types of RFC 1483 ELANs:

•RFC 1483 bridged 802.3. The links can be set up within a single device or with another switch. Multiple RFC 1483 links can be set up within one ELAN. Both LLC and NULL encapsulation are supported.

•RFC 1483 routed IP and IPX. An RFC 1483 routed VLAN always contains only one PVC, corresponding to a point-to-point link between routers. The software adds and removes the MAC header, as appropriate. When configuring an IP and IPX routed circuit, the ATM port must be the only port assigned to the VLAN.

Physical description

The Passport 8672ATME Module (Figure 1) is a single-slot module for the Passport 8600 Series chassis. Online LEDs indicate module operation.

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