Control Word Reserved bit for use in ETree draftdelordpwe3cwbitetree00'txt

1
Control Word Reserved bit for use in
E-Treedraft-delord-pwe3-cw-bit-etree-00.txt

• Simon Delord, Raymond Key Telstra
• Frederic Jounay - France Telecom
• Wim Henderickx - Alcatel-Lucent
• Lucy Yong Huawei
• 76th 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) ---
• --- ---
• --------- ---------
• lt---------- E-Tree ----------gt
• 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) ---
• --- ---
• --------- ---------
• lt---------- E-Tree ----------gt
• 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

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 0L 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