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Configuring I/O Modules

Extreme Networks Consolidated Hardware Guide 257

DSCP Mapping. You can use the diffserv dscp-mapping command to configure a mapped

relationship between an input DSCP and an associated output DSCP. Each PoS port supports three

DSCP mapping tables: one of the tables is used in the ingress direction; two are used for egress flows

(onto the SONET link). The two egress tables are for the congested and noncongested states, as

determined by the RED algorithm. If RED is not enabled on the PoS port, the egress congested-state

mapping table is not used.

In the ingress direction, the input DSCP of a packet received from the SONET link is replaced by an

output DSCP before the packet is forwarded. In the egress direction, the operation is similar, except that

the DSCP mapping occurs before the packet is transmitted onto the SONET link.

One potential use of the DSCP mapping capability is to reconcile varying DiffServ policies at the

boundary between autonomous systems, such as at the boundary between two ISPs. The availability of

different tables for the congested and noncongested states is useful in marking operations that increase

the probability of packets being dropped during times of congestion, as discussed in the DiffServ

Assured Forwarding RFC (RFC 2597).

VLAN ID (VID) Tag Mapping. An analogous feature has been added for managing 802.1Q tags. The

dot1q tagmapping command provides support for VLAN ID (VID) mapping tables. Each PoS port

supports two VID tables: one table is used in the ingress direction; the other is used in the egress

direction. Each of the tables enables an input VID to be mapped to an output VID. This feature is useful

in reconciling policy differences at the boundary between the customer and the service provider.

VLAN ID (VID) Tag Nesting. Another related enhancement provides support for nested 802.1Q tags by

allowing a tag push or tag pop attribute to be associated with a VID. The push attribute indicates that a

new tag is to be added to the frame, while the pop attribute indicates that the top-level tag is to be

removed from the frame. This capability is augmented by an option that allows the 802.1p priority of

the frame to be either preserved or set to a user-configurable value when a new tag is pushed. These

functions make it possible for service providers to tunnel customer-specific VLANs across a common

SONET backbone in a very simple manner.

Port Tunneling. The PoS module also supports port tunneling. Port tunneling can be used to

encapsulate and transport the raw High-Level Data Link Control (HDLC) encapsulated byte stream

from one PoS port to another PoS port across an MPLS network. This allows service providers to tunnel

different types of SONET HDLC streams across a non-SONET backbone like Ethernet.

Software Requirements

The PoS modules require that you run ExtremeWare 7.0 or later on both the MSM64i module and the

PoS module, BootROM 7.8 for the MSM64i module, and BootROM 1.18 for the PoS module.

For more information about software requirements and PoS module configuration, see the ExtremeWare

Software User Guide and the ExtremeWare Command Reference Guide.

Hardware Requirements

The PoS modules are compatible with “i”series MSM modules only. For the most current list of I/O

modules supported for use with the PoS modules, consult your release notes.

PoS modules installed in a BlackDiamond chassis require at least one BlackDiamond Ethernet I/O

module also installed in the chassis in order to operate correctly.

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Extreme Networks WM-4T1i Especificaciones Pagina 257