1. RFC 3036 FECs
RFC 3036 defines FECs used to bind labels to address prefixes in routing table
Two FECs defined:
Address Prefix FEC
Host Address FEC
Not all possible FECs
When labels are bound to other things, need other FECs
E.g., PWE3 defines FECs for binding labels to PWs
E.C.Rosen, MPLS WG
11/9/04

2. HA FEC vs. AP FEC What’s the difference between:
HA FEC and
AP FEC with /32 address?
Some claimed: egress LSR must distinguish, from top label:
whether packet is addressed to it, or
whether packet needs to be forwarded further (i.e., packet tunneled to egress LSR).
So need label which can be used only for 1, never for 2.
E.C.Rosen, MPLS WG
11/9/04

3. Functionality not Needed
LSR Egress specifies HA FEC for its own address
Corresponding label used for management packets address to that LSR
Is this needed?
Was always doubtful
Never been used
The DS needs to remove this functionality
E.C.Rosen, MPLS WG
11/9/04

4. Another Party Heard From
MPLS/FR Forum has proposal using HA FEC
Issues:
Are they really using HA FEC as defined in RFC 3036, or
Are they using only a subset of that functionality, so that the rest can be discarded, or
Are they extending LDP in a way which requires a new FEC?
E.C.Rosen, MPLS WG
11/9/04

5. MPLS Forum’s Proposal CE sends to Ingress PE:
Label Request with HA FEC and Traffic Parms TLV
Makes a resource reservation
Ingress PE responds with label
Same label may be assigned to multiple HA FECs, if they all have the same egress PE
Ingress PE uses label to find corresponding reservation
Ingress PE may base forwarding decision for labeled packet on IP address of packet
E.C.Rosen, MPLS WG
11/9/04

6. Observations on Forum Proposal
Violates RFC 3036/ :
this use of HA FEC does not require a routing table entry for the address
Strange data plane semantics:
“PE may or may not look at IP address”
Suggests that the LSP can only be one hop long
Downstream on Demand only
whereas RFC 3036 defines for DU ordered mode
Forwarding Equivalence Class is set of packets to which a particular resource reservation should be applied
E.C.Rosen, MPLS WG
11/9/04

7. Conclusions New FEC has been implicitly defined
New FEC type must be defined
Resource reservation is part of the FEC
Advantages of using new FEC type:
No issues of how HA FEC is handled or what it means in non-Forum situations (e.g., DU, no reservations)
Use of HA FEC in non-Forum situations would be error
Unused functionality discussed earlier can be eliminated from LDP
Forum can freely define label and FEC semantics without worry of conflict
No impact on non-Forum implementations
E.C.Rosen, MPLS WG
11/9/04