IBM SG24-4817-00 manual This soft copy for use by IBM employees only

This soft copy for use by IBM employees only.

prevent interworking with the IBM ATM switches. This function solves this problem by allowing the the network administrator to set the VPC/VCC range on a given ATM port on the ATM switch, thereby enabling the interworking with non-compliant devices. For example, you can restrict the VPI value equal to 0 and VCI value comprised between 0 and 63 by specifying 0/6 as the VPI/VCI.

Note

If you change the VPI/VCI range for the SSI or NNI port, you must specify the same value on both ends.

•ABR Flow Control Support

On the ATM 12-port 25 Mbps UTP Concentrator module, the ATM 3-port 155 Mbps LAN Concentration module, and on the 12-port 25 Mbps base unit, the end user can add the ATM Forum-compliant available bit rate (ABR) flow control through Explicit Forward Congestion Notification Indication (EFCI) marking. When congestion occurs due to excessive traffic flow, the IBM 8285 and 8260 modules can now mark the EFCI bit in the ATM cells to indicate a congestion condition asking the destination station to notify the source device to reduce its traffic.

•Increase Buffer Size

When multiple ATM sources try to send traffic over one link (for instance the one to which a server is attached), using UBR or ABR class of service, congestion conditions might occur because the aggregate traffic exceeds the capacity of the LAN traffic over ATM. By having a larger buffer size (8,000 cells) the A12-MB25 and A3-MB155 modules are able to absorb bursts of traffic of longer duration, thereby delaying the trigger of the congestion control mechanism, such as Early Packet Discard. This improves the overall response time and relieves end systems from extra frame retransmissions.

•PVC Multipoint Support

In addition to the existing support of point-to-multipoint SVCs, this introduces the smart PVC point-to-multipoint function. Point-to-multipoint trees can be defined now with either fixed permanent virtual paths (PVPs) or fixed permanent virtual channels (PVCs). You only need to define the parameters (VP or VP/VC values) for the root of the tree and the leaves, without any definition for intermediate switches. In case of failure on these intermediate switches, the connections are automatically re-established.

•New 8260 ATM Modules Support

In addition to the control point level V1.2, this level supports the new IBM

8260 ATM modules as follows:

−ATM 3-Port 155 Mbps LAN Concentration Module

•MIB Enhancement (MIB 1.6)

The IBM private MIB for the IBM 8285 is enhanced corresponding to the other announcements.

32ATM Workgroup Solutions: Implementing the 8285 ATM Switch