Extension to VPLS for E-Tree Using Multiple PWs
draft-ram-l2vpn-etree-multiple-pw-00
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| Authors | Rafi Ram , Daniel Cohn , Raymond Key , Puneet Agarwal | ||
| Last updated | 2012-02-13 | ||
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draft-ram-l2vpn-etree-multiple-pw-00
Network Working Group Rafi Ram, Orckit-Corrigent
Internet Draft Daniel Cohn, Orckit-Corrigent
Category: Standard Track Raymond Key, Huawei
P. Agarwal, Broadcom
Yuqun (Sam) Cao, Ruijie Networks
Expires: August 13, 2012
February 13, 2012
Extension to VPLS for E-Tree Using Multiple PWs
draft-ram-l2vpn-etree-multiple-pw-00
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Abstract
This document proposes a solution for Metro Ethernet Forum (MEF)
Ethernet Tree (E-Tree) support in Virtual Private LAN Service using
LDP Signaling (LDP-VPLS) [RFC4762] or BGP signaling (BGP-VPLS)
[RFC4761]. The proposed solution is characterized by the use of two
PWs between a pair of PEs. This solution is applicable for both VPLS
and H-VPLS.
Table of Contents
1. Introduction ................................................... 3
2. Conventions used in this document............................... 3
3. The Problem .................................................... 3
4. The 2-PW Solution .............................................. 4
5. AC E-Tree Type ................................................. 5
6. Extension to LDP-VPLS for E-Tree................................ 5
6.1. VSI E-Tree Type and Identifier.......................... 5
6.1.1. VSI E-Tree Type Encoding .......................... 6
6.1.2. VSI E-Tree Identifier Encoding..................... 6
6.2. Root/Leaf PWs Signaling................................. 6
6.3. Supporting Remote AC.................................... 7
7. Extension to BGP-VPLS for E-Tree................................ 8
7.1. Auto-discovery ......................................... 8
7.2. PW Setup and Teardown................................... 8
7.3. Root/Leaf PWs Signaling................................. 8
7.4. Optimization ........................................... 9
8. Data Forwarding Requirements.................................... 9
9. Backward Compatibility ........................................ 10
9.1. LDP-VPLS .............................................. 10
9.2. BGP-VPLS .............................................. 10
10. Compliance with Requirements.................................. 10
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11. Security Considerations....................................... 10
12. IANA Considerations .......................................... 11
13. Acknowledgements ............................................. 11
14. References ................................................... 11
14.1. Normative References.................................. 11
14.2. Informative References................................ 11
1. Introduction
This document proposes a solution for Metro Ethernet Forum (MEF)
Tree (E-Tree) support in Virtual Private LAN Service using LDP
Signaling (LDP-VPLS) [RFC4762] or BGP Signaling (BGP-VPLS)
[RFC4761].
[Draft ETree VPLS Req] is used as requirement specification.
The proposed solution is characterized by the use of two PWs between
a pair of PEs, which requires extension to the current VPLS
standards [RFC4762] and [RFC4761].
This solution is applicable for both VPLS and H-VPLS.
The proposed solution is composed of three main components:
o Current VPLS standards: LDP-VPLS [RFC4762] and BGP-VPLS
[RFC4761]
o Extensions to the above specified in this document
o PE local split horizon mechanism
2. Conventions used in this document
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].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC-2119 significance.
3. The Problem
[Draft ETree VPLS Req] identifies the problem when there are two or
more PEs with both Root AC and Leaf AC.
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<-----------E-Tree---------->
+---------+ +---------+
| PE1 | | PE2 |
+---+ | +---+ | | +---+ | +---+
|CE1+----AC1----+--+ | | | | +--+----AC3----+CE3|
+---+ (Root AC) | | V | | | | V | | (Root AC) +---+
| | S +--+--PW----+--+ S | |
+---+ | | I | | | | I | | +---+
|CE2+----AC2----+--+ | | | | +--+----AC4----+CE4|
+---+ (Leaf AC) | +---+ | | +---+ | (Leaf AC) +---+
+---------+ +---------+
Figure 1: Problem Scenario for Leaf-to-Leaf Communication
Restriction
When PE2 receives a frame from PE1 via the Ethernet PW:
o PE2 does not know whether the ingress AC is a Leaf AC or not
o PE2 does not have sufficient information to enforce the Leaf-
to-Leaf communication restriction
4. The 2-PW Solution
A simple fix is to carry additional information with each frame on
the PW, indicating whether the frame is originated from a Leaf AC or
a Root AC on the ingress PE.
The proposed solution uses a pair of PWs to interconnect two VPLS
PEs:
o First PW is used for frames originated from Root ACs
o Second PW is used for frames originated from Leaf ACs
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<--------------E-Tree-------------->
+---------+ +---------+
| PE1 | | PE2 |
+---+ | +---+ | | +---+ | +---+
|CE1+----AC1----+--+ | | | | +--+----AC3----+CE3|
+---+ (Root AC) | | V +--+-VSI Root PW -+--+ V | | (Root AC) +---+
| | S | | | | S | |
+---+ | | I +--+-VSI Leaf PW -+--+ I | | +---+
|CE2+----AC2----+--+ | | | | +--+----AC4----+CE4|
+---+ (Leaf AC) | +---+ | | +---+ | (Leaf AC) +---+
+---------+ +---------+
Figure 2: Two-PW Solution for Leaf-to-Leaf Communication Restriction
The next sections specify the required extension to current VPLS
standards.
5. AC E-Tree Type
Each AC connected to a specific VPLS instance on a PE MUST have an
AC E-Tree Type attribute, either Leaf AC or Root AC. For backward
compatibility, the default AC E-Tree Type MUST be Root.
This AC E-Tree Type is locally configured on a PE and no signaling
is required between PEs.
6. Extension to LDP-VPLS for E-Tree
This section specifies extensions to LDP-VPLS [RFC 4762] to support
E-Tree requirements. These extensions apply to both FEC types
specified in [RFC 4762], namely PWid and generalized PWid.
6.1. VSI E-Tree Type and Identifier
Two new PW interface parameters (as defined in section 5.5 of
[RFC4447]) are defined for use in E-Tree VPLS: VSI E-Tree type and
VSI E-Tree identifier.
VSI E-Tree type can be either root or leaf and identifies VSI root
PW and VSI leaf PW respectively, as defined in section 4. ..
VSI E-tree identifier is a number that is used to identify a pair of
root and leaf PW as part of the same logical bridge interface.
The <VSI E-Tree identifier, VSI E-Tree type> pair SHALL be unique
among PWs connecting a pair of VPLS PEs for the same VPLS instance.
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6.1.1. VSI E-Tree Type Encoding
The VSI E-Tree type field is encoded as an interface parameters sub-
TLV (as defined in section 5.5 of [RFC4447]).
The field structure 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length (1) | VSI E-Tree Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
VSI E-tree Type can take the following values:
0 E-Tree Root VSI
1 E-Tree Leaf VSI
6.1.2. VSI E-Tree Identifier Encoding
The VSI E-Tree identifier field is encoded as an interface
parameters sub-TLV (as defined in section 5.5 of [RFC4447]).
The field structure 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type (TBD) | Length (1) | VSI E-Tree Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| VSI E-Tree Identifier(cont.) | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
VSI E-tree Identifier is a 32-bit number that is used to identify a
pair of root and leaf PW as part of the same logical bridge
interface, in the context of a pair of VPLS PEs.
The reserved field SHALL be set to zero.
6.2. Root/Leaf PWs Signaling
Signaling of root and leaf PWs is required only when two PWs are
used for interconnecting between pair of VSIs. As explained in
section 6.1:
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o Root VSI E-Tree type SHALL be used to signal a root PW.
o Leaf VSI E-Tree type SHALL be used to signal a leaf PW.
PW type signaling rules remain as defined in [RFC4447].
It should be noted that in a full-mesh VPLS (as opposed to H-VPLS),
the following VSI pair types do not require two interconnecting PWs:
Root-only VSI <-> any VSI: only root PW required
Leaf-only VSI <-> leaf-only VSI: no PWs required
Where root-only VSI is a VSI where all ACs are of the root type, and
leaf-only VSI is one where all ACs are of the leaf type.
6.3. Supporting Remote AC
When PW is used to interconnect between VSI and a remote AC (e.g.
the PW1, PW2 in Figure 3), an Ethernet Raw or Ethernet tagged PW
types SHALL be used as defined in [RFC4762].
<----------------------E-Tree---------->
+-------+ +-------+
+----+ | PE1 | | PE2 |
+---+ | | | +---+ | | +---+ |
|CE1+---AC1---+----+PW1-+-+ | | | | | | +---+
+---+(Root AC)| | | | | | | | +-+---AC4---+CE4|
|PE-r| | | V +-+VSI Root PW-+-+ V | |(Root AC)+---+
+---+ | | | | | | | | | |
|CE2+---AC2---+----+PW2-+-+ S | | | | S | |
+---+(Leaf AC)| | | | | | | | | |
+----+ | | I +-+VSI Leaf PW-+-+ I | |
+---+ | | | | | | | | +---+
|CE3+--------AC3--------+-+ | | | | +-+---AC5---+CE5|
+---+ (Leaf AC) | +---+ | | +---+ |(Leaf AC)+---+
+-------+ +-------+
Figure 3: VPLS with Remote AC Connectivity
In addition, the AC type i.e. Root or leaf, SHALL be locally
provisioned on the VSI side to specify the remote AC E-Tree Type per
PW. Moreover, such PWs that are used for interconnecting between a
remote AC and a VSI SHALL considered as separate logical bridge
interfaces with respect to MAC address learning/forwarding e.g.
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traffic forwarding between such PWs is allowed as long as they are
not both defined as Leaf.
In Figure 3, AC1 is remotely interconnected to the VPLS service via
PW1, and AC2 is remotely interconnected to the VPLS service via PW2.
AC1 is a Root AC and therefore the local type for PW1 in PE1 SHALL
be Root.
AC2 is a Leaf AC and therefore the local type for PW2 in PE1 SHALL
be Leaf.
7. Extension to BGP-VPLS for E-Tree
This section specifies extensions to BGP-VPLS [RFC 4761] to support
E-Tree requirements.
7.1. Auto-discovery
Requirements in section 3.2.2 of [RFC 4761] apply, with the
following modifications.
Each PE with SHALL advertise two NLRIs for each VPLS instance, with
the same VE-ID and non-overlapping label blocks.
The PE SHALL assign one of the NLRIs for root traffic and the other
one for leaf traffic by setting the root/leaf flag in the attached
Layer2 Info Extended Community, as specified in section 7.2.
7.2. PW Setup and Teardown
Requirements in section 3.2.3 of [RFC 4761] apply, with the
following modifications.
If a PE receives two VPLS NLRI announcements from a remote PE with
the same VE-ID and different root/leaf indication, the PE SHALL set
up two PWs to the remote PE. PW setup for each of the PWs follows
the rules in 3.2.3.
7.3. Root/Leaf PWs Signaling
The Layer2 Info Extended Community attribute is used to indicate
root/leaf assignment for the associated VPLS NLRI.
With reference to Figure 4, bit L in the control flags is defined in
this document. Bits C, S have been defined in [RFC4761].
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0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| MBZ |L|C|S| (MBZ = MUST Be Zero)
+-+-+-+-+-+-+-+-+
Figure 4 - Control Flags Bit Vector
L can take the following values:
0 E-Tree Root VPLS NLRI
1 E-Tree Leaf VPLS NLRI
A PW established following the receipt of a VPLS NLRI with root
assignment will be known as root PW.
A PW established following the receipt of a VPLS NLRI with leaf
assignment will be known as leaf PW.
Two PWs established following the receipt of VPLS NLRIs with the
same VE-ID SHALL be associated to the same logical bridge interface.
7.4. Optimization
As in the LDP case (section 6.2), root and leaf PWs need not be
established between every VSI pair. However, BGP optimization to
avoid root or leaf PW setup in these cases is not considered in this
draft.
8. Data Forwarding Requirements
On frame reception, two PWs associated to the same logical bridge
interface SHALL be handled as a single bridge interface with respect
to MAC address learning/forwarding, e.g. traffic SHALL NOT be
forwarded between such PWs and MAC addresses in frames arriving at
any of the PWs SHALL be learned on a common logical bridge
interface.
On transmission, the VPLS processing entity SHALL send root-
originated traffic via the root PW, and SHALL send leaf-originated
traffic via the leaf PW.
An egress PE SHALL NOT deliver a frame originated at a leaf AC to
another leaf AC.
The following specifies how AC E-Tree type per frame is determined:
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o A frame received from a root PW indicates that the frame was
originated from a root AC.
o A frame received from a leaf PW indicates that the frame was
originated from a leaf AC.
o For the case where both ingress AC and egress AC are on the
same PE, local split horizon implementation on the PE will be
sufficient, and is not further discussed in this document.
9. Backward Compatibility
9.1. LDP-VPLS
Root or leaf VSI E-Tree type and identifier parameters SHALL be used
only in cases where both PEs are VPLS capable and both support E-
Tree extensions defined in this document.
9.2. BGP-VPLS
A PE SHALL announce a leaf VPLS NLRI only to remote PEs that support
E-Tree extensions defined in this document.
10. Compliance with Requirements
This refers to [Draft ETree VPLS Req] Section 5 Requirements.
The solution prohibits communication between any two Leaf ACs in a
VPLS instance.
The solution allows multiple Root ACs in a VPLS instance.
The solution allows Root AC and Leaf AC of a VPLS instance to co-
exist on any PE.
The solution is applicable to LDP-VPLS [RFC4762] and BGP-VPLS
[RFC4762].
The solution is applicable to Case 1: Single technology "VPLS Only".
11. Security Considerations
This will be added in later version.
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12. IANA Considerations
Additional assignments will be required for the new interface
parameter sub-TLV types introduced in Section 4.2. Details will be
added in a later version.
13. Acknowledgements
The authors wish to acknowledge the contributions of Luca Martini
and Amir Halperin.
14. References
14.1. Normative References
[RFC2119] Bradner, S., Key words for use in RFCs to Indicate
Requirement Levels, BCP 14, RFC 2119, March 1997.
[RFC4447] Martini, L., and al, Pseudowire Setup and Maintenance
Using the Label Distribution Protocol (LDP), April 2006
[RFC4762] Lasserre & Kompella, Virtual Private LAN Service (VPLS)
Using Label Distribution Protocol (LDP) Signaling, January 2007
[RFC4761] Rekhter & Kompella, Virtual Private LAN Service (VPLS)
Using BGP for Auto-Discovery and Signaling, January 2007
14.2. Informative References
[Draft VPLS ETree Req] Key, et al., Requirements for MEF E-Tree
Support in VPLS, draft-key-l2vpn-vpls-etree-reqt-04, September 2011
Authors' Addresses
Rafi Ram
Orckit-Corrigent
126 Yigal Alon St.
Tel Aviv, Israel
Email: rafir@orckit.com
Daniel Cohn
Orckit-Corrigent
126 Yigal Alon St.
Tel Aviv, Israel
Email: danielc@orckit.com
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Raymond Key
Huawei
Email: raymond.key@ieee.org
Puneet Agarwal
Broadcom
3151 Zanker Road
San Jose, CA 95134
Email: pagarwal@broadcom.com
Yuqun (Sam) Cao
Ruijie Networks
618 Jinshan Road, Fuzhou 350002, China
Email: yuqun.cao@gmail.com
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