Automatic VLAN allocation in E-tree
draft-chen-l2vpn-vpls-etree-vlan-00
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| Author | Ran Chen | ||
| Last updated | 2012-02-10 | ||
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draft-chen-l2vpn-vpls-etree-vlan-00
Networking Working Group R. Chen
Internet-Draft ZTE Corporation
Intended status: Informational February 10, 2012
Expires: August 13, 2012
Automatic VLAN allocation in E-tree
draft-chen-l2vpn-vpls-etree-vlan-00
Abstract
This document proposes to use automatically allocated VLAN ID to
indicate E-Tree attribute. For the E-Tree requirement, please refer
to [I-D.ietf-l2vpn-etree-reqt] for detail.
Status of this Memo
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This Internet-Draft will expire on August 13, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . . 3
3. Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Allocation mechanism . . . . . . . . . . . . . . . . . . . . . 4
5. Extension to LDP-VPLS for E-tree support . . . . . . . . . . . 5
6. Extension to BGP-VPLS for E-tree support . . . . . . . . . . . 6
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
8.1. Normative references . . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
This document proposes to use automatically allocated VLAN ID to
indicate E-Tree attribute. For the E-Tree requirement, please refer
to [I-D.ietf-l2vpn-etree-reqt] for detail.
In order to achieve better compatibility and traffic optimization,
this document also introduces extensions to existing VPLS protocols
as described in the document.
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 RFC2119.
3. Approach
In order to compatible with IEEE defined E-Tree, the approach in this
draft uses the VLAN ID to indicate Root/Leaf attribute of the frame.
There are two ways to manipulating VLANs for an E-Tree in VPLS:
o Unlike static configuring VLAN in IEEE, VPLS PE has the capability
to create VLAN ID automatically, e.g. The VLAN ID can be derived
from the PW type/AGI automatically via some algorithm;
o Two officially assigned global VLAN ID are allocated by IETF/IEEE,
and the two VLAN ID indicate Root VLAN, Leaf VLAN respectively.
In this document, only the first method is discussed.
Unlike static configuring VLAN ID in IEEE, VPLS PE has the capability
to create VLAN ID automatically, e.g.The VLAN ID can be derived from
the PW type/AGI automatically via some algorithm. As part of VLAN
auto-derive procedure, operators only need to configure the PW type
and the AC Leaf/Root properties, and not necessary to care about the
exact VLAN number. One VLAN ID(Root VLAN ID) is used to indicate the
frame originated from the Root AC and another VLAN ID(Leaf VLAN ID)
is used to indicate the frame originated from the Leaf AC between the
pair of the PEs.
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<-----------------E-Tree----------->
+---------+ +---------+
| PE1 | | PE2 |
+---+ | +----+ | | +----+ | +---+
|CE1|---AC1----|--| | | | | |-|----AC3---|CE3|
+---+(Root AC) | | V | | Ethernet | | V | |(Root AC) +---+
| | S |-|------PW------| | S | |
+---+ | | I | | | | I | | +---+
|CE2|---AC2----|--| | | | | |-|----AC4---|CE4|
+---+(Leaf AC) | +----+ | | +----+ |(Leaf AC) +---+
+---------+ +---------+
Figure 1
As shown in figure 1, the VPLS PE1 and PE2 can both be attached with
root/leaf AC, the VLANs which is used to indicate the Root/leaf can
be derived from the PW type/AGI automatically.
When PE1 receives a frame via the Root AC, PE1 can add the Root VLAN
ID. When PE2 receives the frame from PE1 via the Ethernet PW, PE2
knows the frame originated from the Root, so it can forward the frame
to AC3(Root AC) and AC4 (Leaf AC).
When PE1 receives a frame via the Leaf AC, PE1 can add the leaf VLAN
ID. When PE2 receives the frame from PE1 via the Ethernet PW, PE2
knows the frame originated from the Leaf, so it can forward the frame
to AC3 (Root AC) but it must not be forwarded to any Leaf AC.
The approach allows the egress PE to make a decision whether the
frame can be forwarded or dropped towards a leaf AC. But in some
special scenarios, e.g. one of the VPLS PE is attached with only
leaves, some optimization should be done on the ingress PE to make a
decision whether this frame should be forwarded or dropped. Such
kind of mechanism can improve the bandwidth efficiency. The
extension to VPLS for the PE attached with leaves only is defined in
section 5.
4. Allocation mechanism
As part of VLAN auto-derive procedure, each PE can only need to
configure the Leaf/Root properties for each AC. Both the PWid FEC
element and the Generalized PWid FEC Element can be used to set up
the VPLS as defined in [RFC4762]. "MOD" operation is used to get
Leaf/Root VLAN ID.
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o Root ID = (ID) MOD 4094 + 1;
o Leaf ID = (ID) MOD 4094 + 2.
For the PWid FEC element, if all PWs within VPLS use same PWid, PWid
could be used as the ID, otherwise, PW type could be used as the ID.
For the Generalized PWid FEC, AGI/PW type is used as ID, and AGI is
defined in [RFC5003]. AGI as a VPLS ID would be the same at a
particular VPLS instance, and every PE uses the same "mod" operation
to obtain Leaf/Root VLAN from the VPLS ID. So every PE in the same
VPLS instance obtains the same Root/Leaf VLAN.
In figure 1, assume PE1 and PE2 configure the same PW type 0X0005.
PE1 and PE2 do the "mod" operation: PW type 0X0005 mod 4094, the
calculation result of "6" indicates the frame originated from the
Root, and the calculation result of "7" indicates the frame
originated from the Leaf.
5. Extension to LDP-VPLS for E-tree support
In addition to the signaling procedures for setting up PW as
specified in RFC4447, one new PW interface parameter sub-TLV,the
E-tree sub-TLV, is defined to use in E-Tree VPLS.
The E-tree sub-TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| E-tree (IANA) | Length | Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TPID(optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
In the above figure, reserved bit must be set to 0 when transmitting,
and must be ignored upon receive. P bit is used to flag the PE which
is attached with only leaves as follows:
o P=1: the PE is attached with only leaves;
o P=0: the PE is attached with roots and leaves or is attached with
only roots.
For TPID, it is optional. In various implementations, the TPID is
configurable, if the E-Tree VLAN uses different TPID, it will lead
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some confusion.
If a new TPID value for E-tree is allocated by IEEE, then it is not
necessary to be negotiated in the E-tree sub-TLV.
Otherwise, the TPID should be 16-bit.
Editor's note: it is required for IETF to request IEEE TPID code for
E-Tree if this draft is accepted.
This TLV must be carried in label mapping message. If a PE supports
E-tree service, it must send this E-tree sub-TLV and include its
local TPID value. A PE is attached with only leaves should set the P
bit to 1.
When a PE2 that received such a Label mapping message from its peer
PE1, it knows that the PE1 has the E-tree capability. PE2 should
check if the local configure match the TPID value that carried in the
Label mapping message, and if PE1 is attached with only leaves.
6. Extension to BGP-VPLS for E-tree support
This will be added in later version.
7. IANA Considerations
This document creates a new interface parameter sub-TLV types (E-tree
sub-TLV) that is allocated by IANA, and a value of 0X18 is suggested
for assignment with this sub-TLV.
8. References
8.1. Normative references
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.
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[RFC5003] Metz, C., Martini, L., Balus, F., and J. Sugimoto,
"Attachment Individual Identifier (AII) Types for
Aggregation", RFC 5003, September 2007.
8.2. Informative References
[I-D.ietf-l2vpn-etree-reqt]
Key, R., DeLord, S., JOUNAY, F., Huang, L., Liu, Z., Paul,
M., Kunze, R., Regno, N., and J. Rogers, "Requirements for
MEF E-Tree Support in VPLS",
draft-ietf-l2vpn-etree-reqt-00 (work in progress),
October 2011.
Author's Address
Ran Chen
ZTE Corporation
NO.19 East Huayuan Road
Haidian District Beijing 100191
P.R.China
Email: chen.ran@zte.com.cn
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