Alcatel 1660SM Technical Handbook page 254

ISA–PR may be provisioned to use the following criteria to determine the CoS of the packet:
•
802.1p
– IP TOS/DiffServ
– MPLS Exp
– MPLS Tricolor scheme.
– Fixed CoS; i.e. independent of any indication within the packet.
The rationale for using the Fixed CoS criterion is mostly Customer Equipment inability to support any of
the other criteria.
Layer 2 Based Functionality
Layer 2 Based FunctionalityI herein refers to any decisions, based on MAC address. This includes:
•
identifying the EVC, when provisioned to an E–LAN service
•
selective processing of Layer 2 control protocols.
Both functions above are tightly related to MEF service standards.
When provisioned to an E–LAN service, ISA–PR learns the MAC address of the connected equipment and
forwards packets accordingly.
Layer 2 control protocols are identified using the standard MAC addresses. Selective processing allows
1354BM–PR to provision ISA–PR to either block; i.e. discard the control protocol packets or tunnel; i.e.
forward them. The most useful example is blocking the Spanning Tree at an interface to ISP.
Editing
Editing is not functionally associated with Classification. It is described here because ISA–PR implements
Editing by Network Processor, which also implements Classification. On Classification completion packet
may be optionally edited to modify its header/s.
Supported packet editing options are:
•
append VLAN
•
swap VLAN
•
strip VLAN
•
strip MPLS
The rationale for header editing is needed to mediate between different paradigms, usde by the connecting
networks; e.g.between MPLS and Q–in–Q paradigms; as well as potential tag uniqueness challenges,
when certain values are already in use and therefore require swap to another value.
Classifier is able to process any blend of ingress packet lenghts at wire–speed. Under no circumnstances
will it discard a packet due to inability to process it.
On classification completion Classifier forwards valid packets to the Policer, along with their EVC and CoS
identifiers and the MPLS label identifying the EVC across the ring.
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