System information

10 IBM and Cisco LAN Switching: Interoperability and Migration Guide
bridges. The standard supports eight classes (priorities) of services (COS),
and the LAN devices (switches/bridges), can have any number of
transmission queues on each interface, all the way from one queue for all
traffic to one queue for each transmission priority. High priority frames will be
forwarded before low priority if cut-through mode is not used. A value of 0
means routing services with lowest (no) priority, and a value of 7 might be a
time-critical traffic with highest priority. Typically there are only two queues,
and priorities from 0 to 3 will be forwarded as normal (low),and4to7as
highest priority.
2.1.1.6 Link aggregation
Link aggregation, or trunking, was first implemented by Sun Microsystems for
the purpose of providing more bandwidth between a server and the network.
The SunTrunking 1.0 specification has likely been the basis for several other
proprietary implementations of link aggregations, including Cisco’s
EtherChannel Phase I, to the extent that they interoperate. IBM 8275 Model
416 and on IBM 8371 Model A16 support EtherChannel Phase I. Though not
formally announced, IBM has verified that the link aggregation
implementation of IBM 8275 Models 2xx and 3xx is compatible with
EtherChannel Phase I. We have verified this compatibility and provide a
configuration example in Chapter 3, “Ethernet switch interoperability” on page
25.
The emerging international standard for link aggregation, IEEE 802.3ad, is
barely implemented in commercially available switches. It will likely be the
preferred technology for link aggregation in the future. However, since
SunTrunking and EtherChannel seem to do the job, they will probably be
around for a long time.
2.1.1.7 Layer-3 routing
The following IBM Ethernet switches provide layer-3 functions:
• IBM 8275 Model 416
• IBM 8274 and IBM 8277
• IBM 8371
The functions tested for interoperability are the RIP and OSPF routing
protocols.
In addition to routing, layer-3 equipment often perform several functions that
are internal to the equipment such as filtering and access control lists. Since
these functions are internal to the equipment, they are not an issue for
interoperability, but users must nonetheless verify that equivalent functions