Internet DRAFT - draft-chen-l2vpn-vpls-etree-vlan
draft-chen-l2vpn-vpls-etree-vlan
Networking Working Group R. Chen
Internet-Draft ZTE Corporation
Intended status: Standards Track March 21, 2012
Expires: September 22, 2012
Automatic VLAN allocation in E-tree
draft-chen-l2vpn-vpls-etree-vlan-01
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.
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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 . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative references . . . . . . . . . . . . . . . . . . . 7
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 be 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 manipulate VLANs for an E-Tree in VPLS:
o Static configuring VLAN in IEEE, the Root/Leaf VLAN should co-
ordinate manually or by management plane to be configured same on
all the PEs 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;
Regarding some VPLS PEs have single VLAN space without VLAN
translation, and only support VLAN mapping to VPLS instance, and then
if these PEs want to support VPLS E-tree, static configuring VLAN in
IEEE would be used.
Regarding some VPLS PEs support multiple VLAN spaces, then if these
PEs want to support VPLS E-tree, an optimized approach would be used,
which is automatic allocated VLAN. 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 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 the other
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. In some chips, one VLAN space will not support
all VLANs from 0~4094, then in order to make automatic allocated
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Root/Leaf VLANs be within the VLAN space, so we define this
opertation.
o Root ID = (ID) MOD (Maximum VLAN -Minimum VLAN)+Minimum VLAN + 1 +
offset ;
o Leaf ID = (ID) MOD (Maximum VLAN -Minimum VLAN)+Minimum VLAN + 2 +
offset
For the PWid FEC element, PW type could be used as the ID, then every
PE in all VPLS instances obtains one pair of VLANs indicate Root
VLAN, Leaf VLAN respectively.
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.
For the BGP-VPLS [RFC 4761], Import-RT+Export-RT could be used as ID.
Import-RT+Export-RT would be 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.
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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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:
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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 offset, it should be 16-bit. It is configurable, if the operator
uses different offset, it will lead some confusion.
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 offset 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 offset 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
In addition to the signaling procedures for setting up PW as
specified in [RFC4761], only a new extended community is defined to
use in E-Tree VPLS.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended community type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |P|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3
For offset, it should be 16-bit. It is configurable, if the operator
uses different offset, it will lead some confusion.
P is a Leaf-only bit, it is set to 1 to indicate that the PE is
attached with only leaves, and set to 0 otherwise.
In figure 1, when a PE2 receives BGP UPDATE message with an E-Tree
Extended Community 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 E-Tree Extended Community, and if PE1
is attached with only leaves.
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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.
[RFC4761] Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling",
RFC 4761, January 2007.
[RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service
(VPLS) Using Label Distribution Protocol (LDP) Signaling",
RFC 4762, January 2007.
[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., 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.
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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
Chen Expires September 22, 2012 [Page 8]
