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Tagging Customer Bridge Domains in VPLS
draft-zhang-l2vpn-vpls-bd-tagging-01

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Authors Mingui Zhang , Bin Wang , Liang Xia , Jie Hu
Last updated 2014-02-14
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draft-zhang-l2vpn-vpls-bd-tagging-01
INTERNET-DRAFT                                              Mingui Zhang
Intended Status: Informational                                  Bin Wang
                                                               Liang Xia
                                                                  Huawei
                                                                  Jie Hu
                                                           China Telecom
Expires: August 18, 2014                               February 14, 2014

                Tagging Customer Bridge Domains in VPLS
                draft-zhang-l2vpn-vpls-bd-tagging-01.txt

Abstract

   This document proposes to use Customer VLAN ID as a identifier for
   traffic isolation in Virtual Private LAN Service (VPLS). In this way,
   multiple bridge domains of customers can share a single VPLS instance
   while their traffic are separated. With this proposal, Service
   Providers can be relieved from the heavy provisioning overhead of
   large number of pseudowires in the environment where a mass of bridge
   domains need be connected. 

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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Copyright and License Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors. All rights reserved.

 

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2. Acronyms and Terminology  . . . . . . . . . . . . . . . . . . .  3
     2.1. Acronyms  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     2.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
   3. PE Model  . . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4. Use Cases of U-tag Awareness in VPLS  . . . . . . . . . . . . .  4
     4.1. No Duplicated MAC Address . . . . . . . . . . . . . . . . .  4
     4.2. Scalable Interconnection of L2 Sites  . . . . . . . . . . .  5
     4.3. BUM Traffic Scoped per BD . . . . . . . . . . . . . . . . .  5
       4.3.1. Advertising Interested VLANs in LDP . . . . . . . . . .  5
       4.3.2. Dynamic VLAN Registration with MVRP . . . . . . . . . .  5
     4.4. Per C-VLAN MAC Withdraw . . . . . . . . . . . . . . . . . .  6
   5. Backward Compatibility  . . . . . . . . . . . . . . . . . . . .  6
   6. Contributors  . . . . . . . . . . . . . . . . . . . . . . . . .  6
   7. Security Considerations . . . . . . . . . . . . . . . . . . . .  6
   8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  6
   9. References  . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     9.1. Normative References  . . . . . . . . . . . . . . . . . . .  7
     9.2. Informative References  . . . . . . . . . . . . . . . . . .  7
   Author's Addresses . . . . . . . . . . . . . . . . . . . . . . . .  8

 

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1. Introduction

   VPLS has been widely used to connect customers' bridge domains.
   Traffic segregation for customers is performed on a per VPLS instance
   basis. In the environment (e.g., Data Center Network) where a mass of
   customers multiplied with a plenty of bridge domains are to be
   connected, a large number of PWs need be maintained. Service
   Providers are therefore suffering from scalability issue.

   This proposal suggests the Customer VLAN ID (U-tag) is used as an
   additional de-multiplexor for traffic segregation in VPLS. By doing
   this, multiple BDs can share the same VPLS instance while their
   traffic are isolated. This method can greatly reduce the number of
   PWs therefore reduce the provisioning overhead for operators. Use
   cases of this method are given in the document.

   Two options arising from the industry are covered in the discussion.
   The first one is proposed in [V-aware]. It extends the LDP control
   plane for PEs to advertise supported VLANs. The second option makes
   use of VLAN registration protocol, such as [MVRP], to exchange
   supported C-VLANs between PEs.

2. Acronyms and Terminology

2.1. Acronyms

   MVRP: Multiple VLAN Registration Protocol
   BD: Bridge Domain/Broadcast Domain
   PW: Pseudowire
   VSI: Virtual Switch Instance
   U-tag: Customer VLAN ID
   C-VLAN: Customer VLAN
   BUM: Broadcast, Unknown unicast and Multicast
   VLL: Virtual Leased Line

2.2. Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

3. PE Model

 

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                ........................
                . +--------+           .
      L2 +--------|  BD1   +------------------ PW
      L2 +--------|        |           .
      L2 +---+  . +--------+        VSI.
             |  ........................
             |
             |  ........................
             |  .            +---+---+ .
             |  . +--------+ |100|PKT| .
             +----|  BD11  | +---+---+ .
      L2 +--------|Stag=100+--------------+
                . +--------+           .  |
                .            +---+---+ .  |
                . +--------+ |200|PKT| .  |
      L2 +--------|  BD11  | +---+---+ .  |
                . |Stag=200+--------------+--- tagged PW
                . +--------+           .  |
                .            +---+---+ .  |
                . +--------+ |300|PKT| .  |
      L2 +--------|  BD11  | +---+---+ .  |
      L2 +--------|Stag=300+--------------+
                . +--------+           .
                .                   VSI.
                ........................

      L2 +-----------VLL---------------------- PW

  Figure 3.1: U-tag is used as the service de-multiplexor in tagged PW

   In Figure 3.1, an example is used to shown that service tag is used
   as an finer grained de-multiplexor for traffic segregation.
   Therefore, multiple BDs can be integrated into one VSI.

4. Use Cases of U-tag Awareness in VPLS

4.1. No Duplicated MAC Address

   One MAC address might be used by multiple hosts in different customer
   VLANs (C-VLAN). This is illegal but it is the headache reality for
   providers. In the virtualization environment, Virtual Machines (VM)
   are more likely to have duplicated MAC addresses. When these
   hosts/VMs join in the same VSI of a PE, the PE will see MAC address
   duplication. In order to overcome this issue, the PE has to adopt
   qualified learning [RFC4762], i.e., the PE has to set up one VSI per
   C-VLAN. This brings the scalability issue as discussed in Section
   4.2.

 

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   If the PE uses U-tag as the de-multiplexor to isolate traffic of
   customers' BDs, above MAC address duplication issue can be avoided.

4.2. Scalable Interconnection of L2 Sites

   For the qualified learning, providers need set up one PW per C-VLAN.
   When there is a large number of customers multiplied by C-VLANs
   interconnected using VPLS, a mass of PWs need be maintained. It
   brings heavy operating overhead to providers.

   In this document, U-tag is used to distinguish BDs in VPLS. In this
   way, traffic from multiple C-VLANs can be handled by a single VPLS.
   As shown in Figure 3.1, one PW is set up for each VSI and this VSI
   may be an integration of multiple BDs. Operating overhead of
   operators can be greatly reduced.

4.3. BUM Traffic Scoped per BD

   Traditional VPLS limits a broadcast domain scope per PW. Suppose a
   customer has four sites in New York, Chicago, Atlanta and Dallas. BD1
   = {New York, Chicago and Atlanta} while BD2 = {New York, Chicago and
   Dallas}. If one VSI per PE is set up to interconnect these four
   sites. BUM traffic of Atlanta site will be poured to Dallas site, and
   vice versa.

   When PEs are aware of the U-tag, the BUM traffic can be confined per
   BD with multicast pruning. For above example, the operator need use
   two U-tags to distinguish the two BDs. In this way, BUM traffic of
   Atlanta site will be confined in BD1 and BUM traffic for Dallas site
   will be confined in BD2. This increases the efficiency of the
   bandwidth utilization of BUM traffic.

   Two C-VLAN based multicast pruning techniques are listed below. (One
   is give in [V-aware] the other has been implemented by vendors.)

4.3.1. Advertising Interested VLANs in LDP

   With the PW VLAN Vector TLV defined in [V-aware], PEs can advertise
   in LDP the interested C-VLANs for its interfaces. In this way, PEs
   can prune the flooding on a per C-VLAN basis.

4.3.2. Dynamic VLAN Registration with MVRP

   It requires Multiple VLAN Registration Protocol (MVRP) to be
   supported by PEs for U-tag registration on the interfaces providing
   VPLS. With the help of MVRP, operators need not manually configure C-
   VLANs on PEs.

 

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   Only when a C-VLAN is registered in both directions of a PW, this PW
   will not be eliminated for this C-VLAN. Otherwise, this PW will be
   pruned for this C-VLAN. Multicast frames for a C-VLAN SHOULD only be
   forwarded on PWs that are not pruned for this C-VLAN.

4.4. Per C-VLAN MAC Withdraw

   With the awareness of U-tag, PEs can achieve a finer gained C-VLAN
   scoped MAC withdraw. For example, with the VLAN Vector TLV defined in
   [V-aware], a PE can specify VLANs that it wants their MAC address to
   be flushed.

5. Backward Compatibility

   Two PEs need negotiate their capability on supporting the awareness
   of U-tag. Unless both PEs is aware of U-tag, the tagged PW cannot be
   established. When a PE realizes the peering PE's interface is unaware
   of U-tag, it MUST fall back to establish a raw PW with this
   interface.

   There are two ways to achieve the capability negotiation. 

      a) As defined in Section 4 of [V-aware], PEs can negotiate this
         capability through LDP using the VLAN Aware Capability TLV.

      b) A tagged PW is established between two interfaces if they both
         enable MVRP.

   For the tagged PW, PEs can achieve customer VLAN scoped MAC address
   flushing [V-aware]. However, PEs may as well send out the old type
   MAC withdraw message per Section 6.2 of [RFC4762]. The receiver PE
   parses this kind of message as that the peering PE is flushing MAC
   addresses across all customer VLANs supported by this PW.

6. Contributors

   Xingjian He, Huawei

7. Security Considerations

   This document raises no new security issues. For general security
   considerations, refer to [RFC4761] and [RFC4762].

8. IANA Considerations

   This document requires no IANA actions. RFC Editor: please remove
   this section before publication.

 

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9. References 

9.1. Normative References

   [V-aware] D. Cai, S. Boutros, and et al, "VLAN Aware VPLS services",
             draft-cai-l2vpn-vpls-vlan-aware-bundling-00.txt, working in
             progress.

   [MVRP]    IEEE P802.1ak/D8.0, "IEEE Standard for Local and
             Metropolitan Area Networks: Virtual Bridged Local Area
             Networks -- Amendment 07: Multiple Registration Protocol",
             November 29, 2006.

   [RFC4762] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private
             LAN Service (VPLS) Using Label Distribution Protocol (LDP)
             Signaling", RFC 4762, January 2007.

9.2. Informative References

   [RFC4761] Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual Private
             LAN Service (VPLS) Using BGP for Auto-Discovery and
             Signaling", RFC 4761, January 2007.

 

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Author's Addresses

   Mingui Zhang
   Huawei Technologies
        
   Email: zhangmingui@huawei.com

   Bin Wang
   Huawei Technologies

   Email: wb.wangbin@huawei.com

   Liang Xia
   Huawei Technologies

   Email: frank.xialiang@huawei.com

   Jie Hu
   China Telecom

   Email: hujie@ctbri.com.cn

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