1. Control Word Reserved bit for use in E-Tree draft-delord-pwe3-cw-bit-etree-00.txt Simon Delord, Raymond Key – Telstra Frederic Jounay - France Telecom Wim Henderickx - Alcatel-Lucent Lucy Yong – Huawei 76 th IETF, November 2009

2. E-Tree An Ethernet VPN in which each Root AC can communicate with every other AC, whereas Leaf ACs can only communicate with Root ACs. Each AC on an E-Tree construct is designated as either a Root AC or a Leaf AC. There can be multiple Root ACs and Leaf ACs per E-Tree construct.

3. VPLS for E-Tree +---------+ +---------+ | PE1 | | PE2 | | | | | +---+ | +---+ | | +---+ | +---+ |CE1+-----AC1----+--+ | | | | +--+----AC3-----+CE3| +---+ (Root AC) | | V | | | | V | | (Root AC) +---+ | | | | Ethernet | | | | | | S +--+----PW----+--+ S | | +---+ | | | | | | | | +---+ |CE2+-----AC2----+--+ I | | | | I +--+----AC4-----+CE4| +---+ (Leaf AC) | | | | | | | | (Leaf AC) +---+ | +---+ | | +---+ | | | | | +---------+ +---------+ Ingress frame at a Leaf AC - can only be delivered to one or more Root ACs - MUST NOT be delivered to any Leaf ACs

4. Problem +---------+ +---------+ | PE1 | | PE2 | | | | | +---+ | +---+ | | +---+ | +---+ |CE1+-----AC1----+--+ | | | | +--+----AC3-----+CE3| +---+ (Root AC) | | V | | | | V | | (Root AC) +---+ | | | | Ethernet | | | | | | S +--+----PW----+--+ S | | +---+ | | | | | | | | +---+ |CE2+-----AC2----+--+ I | | | | I +--+----AC4-----+CE4| +---+ (Leaf AC) | | | | | | | | (Leaf AC) +---+ | +---+ | | +---+ | | | | | +---------+ +---------+ When PE2 receives a frame from PE1 via the Ethernet PW -PE2 not know whether it is from AC1 or AC2 -PE2 not know whether it is from Leaf AC or Root AC -PE2 can’t decide whether it can be forwarded to AC4

5. A Simple Fix Carry additional one bit of information (0 or 1) for each payload Ethernet frame on PW -Indicate whether the frame is from a Leaf AC on the Ingress PE or not -Based on this one bit of information, the Egress PE can decide whether the frame can be forwarded to a local Leaf AC or not Where to put this one bit? +------------+----------+-----------------------+------------------------+ | MPLS Label | VC Label | Optional Control Word | Payload Ethernet Frame | +------------+----------+-----------------------+------------------------+ Any “reserved for future use” bit in the current PWE3 standard can be used for this per-payload signaling?

6. RFC 4385 PWE3 Control Word for Use over an MPLS PSN To provide consistency between the designs of different types of PW, it SHOULD also use the following preferred format: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0| Flags |FRG| Length | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Preferred PW MPLS Control Word Flags (bits 4 to 7): These bits MAY be used by for per-payload signaling. Their semantics MUST be defined in the PW specification.

7. RFC 4448 Encapsulation of Ethernet over MPLS The control word is defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0| Reserved | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ In the above diagram, the first 4 bits MUST be set to 0 to indicate PW data. The rest of the first 16 bits are reserved for future use. They MUST be set to 0 when transmitting, and MUST be ignored upon receipt.

8. Extension to RFC 4448 Encapsulation of Ethernet over MPLS The control word is defined as follows: 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0|L| Reserved | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ In the above diagram, the first 4 bits MUST be set to 0 to indicate PW data. Leaf bit (L) The L-bit is used to flag the presence of an Ethernet frame from a Leaf AC as follows: L = 1 The Ethernet Frame comes from a Leaf AC L = 0 The Ethernet Frame comes from a Root AC The rest of the first 16 bits are reserved for future use. They MUST be set to 0 when transmitting, and MUST be ignored upon receipt. RFC 4447 sufficient. No new PW signaling required.

9. Control Word L-bit This Internet Draft is to seek allocation of one bit in the Control Word of PWE3 Ethernet Encapsulation. Actually, any one bit in bit 4-7 would do, up to the PWE3 Workgroup. This Control Word L-bit is a mandatory component of the proposed solution for enhancing VPLS to support E-Tree. Two Internet Drafts submitted to the L2VPN Workgroup cover more details on the overall solution. “Extension to VPLS for E-Tree” (draft-key-l2vpn-vpls-etree-00.txt) “A Framework for E-Tree Service over MPLS Network” (draft-key-l2vpn-etree-frwk-00.txt)

10. Thank You Very Much Please post questions & comments on workgroup mailing list, or talk/email to the authors direct