Internet Working Group Y. Jiang, Ed.
Internet Draft L. Yong
Intended status: Standards Track Huawei
M. Paul
Deutsche Telekom
Expires: August 2015 February 26, 2015
Ethernet-Tree (E-Tree) Support in Virtual Private LAN Service (VPLS)
draft-ietf-l2vpn-vpls-pe-etree-05.txt
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Abstract
A generic Virtual Private LAN Service (VPLS) solution is specified
for Ethernet-Tree (E-Tree) services which uses VLANs to indicate root
or leaf traffic. A VPLS Provider Edge (PE) model is illustrated as an
example for the solution. In the solution, E-Tree VPLS PEs are
interconnected by PWs which carry the VLAN indicating the E-Tree
attribute, the MAC address based Ethernet forwarding engine and the
PW work in the same way as before. A signaling mechanism for E-Tree
capability and VLAN mapping negotiation is further described.
Table of Contents
1. Conventions used in this document ......................... 2
2. Terminology ............................................... 3
3. Introduction .............................................. 4
4. PE Model with E-Tree Support .............................. 5
4.1. Existing PE Models ..................................... 5
4.2. A New PE Model with E-Tree Support ..................... 8
5. PW for E-Tree Support ..................................... 9
5.1. PW Encapsulation ....................................... 9
5.2. VLAN Mapping ........................................... 9
5.3. PW Processing ......................................... 11
5.3.1. PW Processing in the VLAN Mapping Mode .......... 11
5.3.2. PW Processing in the Compatible Mode ............ 12
5.3.3. PW Processing in the Optimized Mode ............. 13
6. Signaling for E-Tree Support ............................. 14
6.1. LDP Extensions for E-Tree Support ..................... 14
6.2. BGP Extensions for E-Tree Support ..................... 16
7. OAM Considerations ....................................... 18
8. Applicability ............................................ 18
9. Security Considerations .................................. 18
10. IANA Considerations ...................................... 19
11. References ............................................... 19
11.1. Normative References ............................... 19
11.2. Informative References ............................. 20
12. Acknowledgments .......................................... 21
Appendix A. Other PE Models for E-Tree ........................ 22
A.1. A PE Model With a VSI and No bridge ................... 22
A.2. A PE Model With external E-Tree interface ............. 23
1. 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].
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2. Terminology
AC: Attachment Circuit
B-VLAN: Backbone VLAN
C-VLAN: Customer VLAN
E-Tree: Ethernet Tree, a Rooted-Multipoint EVC service as defined in
MEF 6.1
EVC: Ethernet Virtual Connection, as defined in MEF 4.0
FIB: Forwarding Information Base, also known as forwarding table
I-SID: Backbone Service Instance Identifier, as defined in IEEE
802.1ah
Leaf AC: an AC attached with a leaf
Leaf VLAN: a VLAN Identifier (ID) used to indicate all the frames
that are originated at a leaf AC
OAM: Operations, Administration and Maintenance
PBB: Provider Backbone Bridge
PE: Provider Edge
PW: Pseudo Wire
Root AC: an AC attached with a root
Root VLAN: a VLAN ID used to indicate all the frames that are
originated at a root AC
S-VLAN: Service VLAN
T-VSI: Tree VSI, a VSI with E-Tree support
VLAN: Virtual Local Area Network
VPLS: Virtual Private LAN Service
VSI: Virtual Switching Instance as defined in [RFC4664], also known
as VPLS Forwarder in [RFC7041]
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3. Introduction
The Ethernet-Tree (E-Tree) service is defined in Metro Ethernet Forum
(MEF) Technical Specification MEF 6.1 as a Rooted-Multipoint Ethernet
Virtual Connection (EVC) service. It is a multipoint Ethernet service
with special restrictions: the Ethernet frames from a root may be
received by any other root or leaf, and the frames from a leaf may be
received by any root, but MUST not be received by a leaf. Further, an
E-Tree service may include multiple roots and multiple leaves.
Although Virtual Private Multicast Service (VPMS) [VPMS] or Point-to-
Multipoint (P2MP) multicast is a somewhat simplified version of this
service, in fact, there is no exact corresponding terminology in IETF
yet.
[RFC7152] gives the requirements for providing E-Tree solutions in
the VPLS and the need to filter leaf-to-leaf traffic. [RFC7387]
further describes a Multiprotocol Label Switching (MPLS) framework
for providing E-Tree. Though there were proposals on using PW control
word or PWs to indicate the root/leaf attribute of an E-Tree frame,
both methods are limited in that they are only applicable to "VPLS
only" networks.
In fact, VPLS PE usually consists of a bridge module itself (see
[RFC4664] and [RFC6246]); moreover, E-Tree services may cross both
Ethernet and VPLS domains. Therefore, it is necessary to develop an
E-Tree solution both for "VPLS only" scenarios and for interworking
between Ethernet and VPLS.
IEEE 802.1 has incorporated the generic E-Tree solution in the latest
version of 802.1Q [802.1Q-2011], which is just an improvement on the
traditional asymmetric VLAN mechanism (the use of different VLANs to
indicate E-Tree root/leaf attributes and prohibiting leaf-to-leaf
traffic with the help of VLANs was first standardized in IEEE 802.1Q-
2003). In the new IEEE 802.1Q solution, VLANs are used to indicate
root/leaf attribute of a frame: one VLAN ID is used to indicate the
frames originated from the roots and another VLAN ID is used to
indicate the frames originated from the leaves. At a leaf port, the
bridge can then filter out all the frames from other leaf ports based
on the VLAN ID. It is better to reuse the same mechanism in VPLS than
to develop a new mechanism. The latter will introduce more complexity
to interwork with the new IEEE 802.1Q solution.
This document specifies how the Ethernet VLAN solution can be used to
support generic E-Tree services in VPLS. The solution specified here
is fully compatible with the IEEE bridge architecture and with IETF
Pseudo Wire Emulation Edge-to-Edge (PWE3) technology, thus it will
not change the FIB (such as installing E-Tree attributes in the FIB),
or need any specially tailored implementation. Furthermore, VPLS
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scalability and simplicity are also well kept. With this mechanism,
it is also convenient to deploy a converged E-Tree service across
both Ethernet and MPLS networks.
Firstly, a typical VPLS PE model is introduced as an example; the
model is then extended in which a Tree VSI is connected to a VLAN
bridge with a dual-VLAN interface.
This document then discusses the PW encapsulation and PW processing
such as VLAN mapping options for transporting E-Tree services in VPLS.
Finally, it describes the signaling extensions and processing
procedures for E-Tree support in VPLS.
4. PE Model with E-Tree Support
The problem scenario of E-Tree as shown in Fig. 1 of [RFC7152] is a
simplification of the L2VPN architecture, several common VPLS PE
architectures are discussed in more details in [RFC4664] and
[RFC6246].
Therefore, E-Tree solution in VPLS is demonstrated with the help of a
typical VPLS PE model. It can also be used in other PE models which
are discussed in Appendix A.
4.1. Existing PE Models
According to [RFC4664], there are at least three models possible for
a VPLS PE, including:
o A single bridge module, a single VSI;
o A single bridge module, multiple VSIs;
o Multiple bridge modules, each attaches to a VSI.
The second PE model is commonly used. A typical example is further
depicted in Fig. 1 and Fig. 2 (both figures are extracted from
[RFC6246]), where an S-VLAN bridge module is connected to multiple
VSIs each with a single VLAN virtual interface.
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+-------------------------------+
| 802.1ad Bridge Module Model |
| |
+---+ AC | +------+ +-----------+ |
|CE |---------|C-VLAN|------| | |
+---+ | |bridge|------| | |
| +------+ | | |
| o | S-VLAN | |
| o | | | ---> to VSI
| o | Bridge | |
+---+ AC | +------+ | | |
|CE |---------|C-VLAN|------| | |
+---+ | |bridge|------| | |
| +------+ +-----------+ |
+-------------------------------+
Figure 1 A model of 802.1ad Bridge Module
+----------------------------------------+
| VPLS-capable PE model |
| +---------------+ +------+ |
| | | |VSI-1 |------------
| | |==========| |------------ PWs
| | Bridge ------------ |------------
| | | S-VLAN-1 +------+ |
| | Module | o |
| | | o |
| | (802.1ad | o |
| | bridge) | o |
| | | o |
| | | S-VLAN-n +------+ |
| | ------------VSI-n |-------------
| | |==========| |------------- PWs
| | | ^ | |-------------
| +---------------+ | +------+ |
| | |
+-------------------------|--------------+
LAN emulation Interface
Figure 2 A VPLS-capable PE Model
In this PE model, Ethernet frames from Customer Edges (CEs) will
cross multiple stages of bridge modules (i.e., C-VLAN and S-VLAN
bridge) and a VSI in a PE before being sent on the PW to a remote PE.
Therefore, the association between an AC port and a PW on a VSI is
difficult, sometimes even impossible.
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This model could be further enhanced: When Ethernet frames arrive at
a PE, a root VLAN or a leaf VLAN tag is added. Then the frames with
the root VLAN tag are transmitted both to the roots and the leaves,
while the frames with the leaf VLAN tag are transmitted to the roots
but dropped for the leaves (these VLAN tags are removed before the
frames are transmitted over the wire). It was demonstrated in
[802.1Q-2011] that the E-Tree service in Ethernet networks can be
well supported with this mechanism.
Assuming this mechanism is implemented in the bridge module, it is
quite straightforward to infer a VPLS PE model with two VSIs to
support the E-Tree (as shown in Fig. 3). But this model will require
two VSIs per PE and two sets of PWs per E-Tree service, which is
poorly scalable in a large MPLS/VPLS network; in addition, both these
VSIs have to share their learned MAC addresses.
+----------------------------------------+
| VPLS-capable PE model |
| +---------------+ +------+ |
| | | |VSI-1 |------------
| | |==========| |------------ PWs
| | Bridge ------------ |------------
| | | Root +------+ |
| | Module | S-VLAN |
| | | |
| | (802.1ad | |
| | bridge) | |
| | | Leaf |
| | | S-VLAN +------+ |
| | ------------VSI-2 |-------------
| | |==========| |------------- PWs
| | | ^ | |-------------
| +---------------+ | +------+ |
| | |
+-------------------------|--------------+
LAN emulation Interface
Figure 3 A VPLS PE Model for E-Tree with 2 VSIs
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4.2. A New PE Model with E-Tree Support
In order to support the E-Tree in a more scalable way, a new VPLS PE
model with a single Tree VSI (T-VSI, a VSI with E-Tree support) is
specified. As depicted in Fig. 4, the bridge module is connected to
the T-VSI with a dual-VLAN virtual interface, i.e., both the root
VLAN and the leaf VLAN are connected to the same T-VSI, and they
share the same FIB and work in shared VLAN learning. In this way,
only one VPLS instance and one set of PWs is needed per E-Tree
service, and the scalability of VPLS is improved.
+----------------------------------------+
| VPLS-capable PE model |
| +---------------+ +------+ |
| | |==========|TVSI-1|------------
+---+AC | | ------------ |------------ PWs
|CE |-------| Bridge ------------ |------------
+---+ | | | Root & +------+ |
| | Module | Leaf VLAN o |
| | | o |
| | | o |
| | | o |
| | | o |
+---+AC | | | VLAN-n +------+ |
|CE |-------| ------------VSI-n |-------------
+---+ | | |==========| |------------- PWs
| | | ^ | |-------------
| +---------------+ | +------+ |
| | |
+-------------------------|--------------+
LAN emulation Interface
Figure 4 A VPLS PE Model for E-Tree with a Single T-VSI
For an untagged port (frames over this port are untagged) or VLAN-
unaware port (VLAN tags in the frames are ignored), the Ethernet
frames received from the root ACs SHOULD be tagged with a root C-VLAN,
and optionally MAY be added with another root S-VLAN.
For a C-VLAN tagged port, the Ethernet frames received from the root
ACs SHOULD be added with a root S-VLAN.
For an S-VLAN tagged port, the S-VLAN tag in the Ethernet frames
received from the root ACs SHOULD be translated to the root S-VLAN in
the VPLS network domain. Alternatively, the PBB VPLS PE model (where
an IEEE 802.1ah bridge module is embedded in the PE) as described in
[RFC7041] MAY be used, and a root B-VLAN or leaf B-VLAN MAY be added
in this case (the E-Tree attribute may also be indicated with two I-
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SID tags in the bridge module, and the frames are further
encapsulated and transported transparently over a single B-VLAN, thus
the PBB VPLS works just in the same way as described in [RFC7041] and
will be discussed no more in this document). When many S-VLANs are
multiplexed in a single AC, the 2nd option has an advantage of both
VLAN scalability and MAC address scalability.
In a similar way, the traffic from the leaf ACs is tagged and
transported on the leaf C-VLAN, S-VLAN or B-VLAN.
In all cases, the outermost VLAN in the resulted Ethernet header is
used to indicate the E-Tree attribute of an Ethernet frame; this
document uses VLAN to refer to this outermost VLAN for simplicity in
the latter sections.
5. PW for E-Tree Support
5.1. PW Encapsulation
To support an E-Tree service, T-VSIs in a VPLS MUST be interconnected
with a bidirectional Ethernet PW. The Ethernet PW SHOULD work in the
tagged mode (PW type 0x0004) as described in [RFC4448], in which case
a VLAN tag MUST be carried in each frame in the PW to indicate the
frame originated from either root or leaf (the VLAN tag indicating
the frame originated from either root or leaf can be translated by a
bridge module in the PE or added by an outside Ethernet edge device,
even by a customer device). In the tagged PW mode, two service
delimiting VLANs MUST be allocated in the VPLS domain for an E-Tree.
PW processing for the tagged PW will be described in Section 5.3 of
this document.
Raw PW (PW type 0x0005 in [RFC4448]) MAY also be used to carry E-Tree
service for a PW in Compatible mode as shown in Section 5.3.2.
5.2. VLAN Mapping
There are two ways of manipulating VLANs for an E-Tree in VPLS:
o Global VLAN based, that is, provisioning two global VLANs (Root
VLAN, Leaf VLAN) across the VPLS network, thus no VLAN mapping is
needed at all, or the VLAN mapping is done completely in the
Ethernet domains.
o Local VLAN based, that is, provisioning two local VLANs for each
PE (which participates in the E-Tree) in the VPLS network
independently.
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The first method requires no VLAN mapping in the PW, but two unique
service delimiting VLANs must be allocated across the VPLS domain.
The second method is more scalable in the use of VLANs, but needs a
VLAN mapping mechanism in the PW similar to what is already described
in Section 4.3 of [RFC4448].
Global or local VLANs can be manually configured or provisioned by an
Operational Support System. Alternatively, some automatic VLAN
allocation algorithm may be provided in the management plane, but it
is out scope of this document.
For both methods, VLAN mapping parameters from a remote PE can be
provisioned or determined by a signaling protocol as described in
Section 6 when a PW is being established.
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5.3. PW Processing
5.3.1.PW Processing in the VLAN Mapping Mode
In the VLAN Mapping mode, two VPLS PEs with E-Tree capability are
inter-connected with a PW (For example, the scenario of Fig. 5
depicts the interconnection of two PEs miscellaneously attached with
both root and leaf nodes).
+----------------------------+
| VPLS PE with T-VSI |
| |
+----+ | +------+ Root VLAN +-----+ | PW
|Root|------| VLAN |-----------|T-VSI|----------
+----+ | | BRG | Leaf VLAN | |----------
+----+ | | |-----------| |----------
|Leaf|------| | | |-----+
+----+ | +------+ +-----+ | |
| | |
+----------------------------+ |
|
+----------------------------+ |
| VPLS PE with T-VSI | |
| | |
+----+ | +------+ Root VLAN +-----+ | | PW
|Root|------| VLAN |-----------|T-VSI|-----+
+----+ | | BRG | Leaf VLAN | |----------
+----+ | | |-----------| |----------
|Leaf|------| | | |----------
+----+ | +------+ +-----+ |
| |
+----------------------------+
Figure 5 T-VSI Interconnected in the Normal Mode
If a PE is in the VLAN mapping mode for a PW, then in the data plane
the PE MUST map the VLAN in each frame as follows:
o Upon transmitting frames on the PW, map from local VLAN to remote
VLAN (i.e., the local leaf VLAN in a frame is translated to the
remote leaf VLAN; the local root VLAN in a frame is translated to the
remote root VLAN).
o Upon receiving frames on the PW, map from remote VLAN to local VLAN,
and the frames are further forwarded or dropped in the egress bridge
module using the filtering mechanism as described in [802.1Q-2011].
The signaling for VLANs used by E-Tree is specified in Section 6.
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5.3.2.PW Processing in the Compatible Mode
The new VPLS PE model can work in a traditional VPLS network
seamlessly in the compatibility mode. As shown in Fig. 6, the VPLS PE
with T-VSI can be attached with root and/or leaf nodes, while the
VPLS PE with a traditional VSI can only be attached with root nodes.
A raw PW SHOULD be used to connect them.
+------------------------+
| VPLS PE with T-VSI |
| |
+----+ | +------+ +-----+ | PW
|Root|------| VLAN |-------|T-VSI|----------
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |---------+
+----+ | +------+ +-----+ | |
| | |
+------------------------+ |
|
+------------------------+ |
| VPLS PE with VSI | |
| | |
+----+ | +------+ +-----+ | PW |
|Root|------| VLAN |-------|VSI |---------+
+----+ | | BRG | | |----------
+----+ | | | | |----------
|Root|------| | | |----------
+----+ | +------+ +-----+ |
| |
+------------------------+
Figure 6 T-VSI interconnected with Traditional VSI
If a PE is in the Compatible mode for a PW, then in the data plane
the PE MUST process the frame as follows:
o Upon transmitting frames on the PW, remove the root or leaf VLAN in
the frames.
o Upon receiving frames on the PW, add a VLAN tag with a value of the
local root VLAN to the frames.
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5.3.3.PW Processing in the Optimized Mode
When two PEs (both have E-Tree capability) are inter-connected and
one of them (e.g., PE2) is attached with only leaf nodes, as shown in
the scenario of Fig. 7, its peer PE (e.g., PE1) should then work in
the optimized mode. In this case, PE1 should not send the frames
originated from the local leaf VLAN to PE2, i.e., these frames are
dropped rather than transported over the PW. The bandwidth efficiency
of the VPLS can thus be improved. The signaling for the PE attached
with only leaf nodes is specified in Section 6.
+------------------------+
|VPLS PE with T-VSI (PE1)|
| |
+----+ | +------+ +-----+ | PW
|Root|------| VLAN |-------|T-VSI|----------
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |---------+
+----+ | +------+ +-----+ | |
| | |
+------------------------+ |
|
+------------------------+ |
|VPLS PE with T-VSI (PE2)| |
| | |
+----+ | +------+ +-----+ | PW |
|Leaf|------| VLAN |-------|T-VSI|---------+
+----+ | | BRG | | |----------
+----+ | | |-------| |----------
|Leaf|------| | | |----------
+----+ | +------+ +-----+ |
| |
+------------------------+
Figure 7 T-VSI interconnected with PE attached with only leaf nodes
If a PE is in the Optimized Mode for a PW, upon transmit, the PE
SHOULD first operate as follows:
o Drop a frame if its VLAN ID matches the local leaf VLAN ID.
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6. Signaling for E-Tree Support
6.1. LDP Extensions for E-Tree Support
In addition to the signaling procedures as specified in [RFC4447],
this document specifies a new interface parameter sub-TLV to
provision an E-Tree service and negotiate the VLAN mapping function,
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(0x1A) | Length=8 | Reserved |P|V|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Root VLAN ID | Leaf VLAN ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8 E-Tree Sub-TLV
Where:
o E-Tree is the sub-TLV identifier (0x1A) as assigned by IANA.
o Length is the length of the sub TLV in octets.
o Reserved bits MUST be set to zero on transmit and be ignored on
receive.
o P is a Leaf-only bit, it is set to 1 to indicate that the PE is
attached with only leaf nodes, and set to 0 otherwise.
o V is a bit indicating the sender's VLAN mapping capability. A PE
capable of VLAN mapping MUST set this bit, and clear it otherwise.
o Root VLAN ID is the value of the local root VLAN.
o Leaf VLAN ID is the value of the local leaf VLAN.
When setting up a PW for the E-Tree based VPLS, two peer PEs
negotiate the E-Tree support using the above E-Tree sub-TLV. Note PW
type of 0x0004 SHOULD be used during the PW negotiation.
A PE that wishes to support E-Tree service MUST include an E-Tree
Sub-TLV in its PW label mapping message and include its local root
VLAN ID and leaf VLAN ID in the TLV. A PE that has the VLAN mapping
capability MUST set the V bit to 1, and a PE is attached with only
leaf nodes SHOULD set the P bit to 1.
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In default, for each PW, VLAN-Mapping-Mode, Compatible-Mode, and
Optimized-Mode are all set to FALSE.
A PE that receives a PW label mapping message with an E-Tree Sub-TLV
from its peer PE, after saving the VLAN information for the PW, MUST
process it as follows:
1) if the root and leaf VLAN ID in the message match the local root
and leaf VLAN ID, then continue to 3);
2) else {
if the bit V is cleared, then {
if the PE is capable of VLAN mapping, then it MUST set
VLAN-Mapping-Mode to TRUE;
else {
A label release message with the error code "E-Tree
VLAN mapping not supported" is sent to the peer PE
and exit the process;
}
}
if the bit V is set, and the PE is capable of VLAN mapping,
then the PE with the minimum IP address MUST set VLAN-Mapping-
Mode to TRUE;
}
3) If the P bit is set, then:
{
If the PE is a leaf-only node itself, then a label release
message with a status code "Leaf to Leaf PW released" is sent to
the peer PE and exit the process;
Else the PE SHOULD set the Optimized-Mode to TRUE.
}
If a PE has sent an E-Tree Sub-TLV but does not receive any E-Tree
Sub-TLV in its peer's PW label mapping message, The PE SHOULD then
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establish a raw PW with this peer as in traditional VPLS and set
Compatible-Mode to TRUE for this PW.
Data plane processing for this PW is as following:
If Optimized-Mode is TRUE, then data plane processing as described in
Section 5.3.3 applies.
If VLAN-Mapping-Mode is TRUE, then data plane processing as described
in Section 5.3.1 applies.
If Compatible-Mode is TRUE, then data plane processing is as
described in Section 5.3.2.
PW processing as described in [RFC4448] proceeds as usual for all
cases.
6.2. BGP Extensions for E-Tree Support
A new E-Tree extended community (0x800b) is allocated by IANA for E-
Tree signaling in BGP VPLS:
+------------------------------------+
| Extended community type (2 octets) |
+------------------------------------+
| Root VLAN (2 octets) |
+------------------------------------+
| Leaf VLAN (2 octets) |
+------------------------------------+
| Reserved |P|V|
+------------------------------------+
Figure 9 E-Tree Extended Community
Where:
o Root VLAN ID is the value of the local root VLAN.
o Leaf VLAN ID is the value of the local leaf VLAN.
o Reserved, 14 bits MUST be set to zero on transmit and be ignored
on receive.
o P is a Leaf-only bit, it is set to 1 to indicate that the PE is
attached with only leaf nodes, and set to 0 otherwise.
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o V is a bit indicating the sender's VLAN mapping capability. A PE
capable of VLAN mapping MUST set this bit, and clear it otherwise.
The PEs attached with both leaf and root nodes MUST support BGP E-
Tree signaling as described in this document, and SHOULD support VLAN
mapping in their data planes. The traditional PE attached with only
root nodes may also participate in an E-Tree service. If some PEs
don't support VLAN mapping, global VLANs as per Section 5.2 MUST be
provisioned for an E-Tree service.
In BGP VPLS signaling, besides attaching a Layer2 Info Extended
Community as detailed in [RFC4761], an E-Tree Extended Community MUST
be further attached if a PE wishes to participate in an E-Tree
service. The PE MUST include its local root VLAN ID and leaf VLAN ID
in the E-Tree Extended Community. A PE attached with only leaf nodes
of an E-Tree SHOULD set the P bit in the E-Tree Extended Community to
1.
A PE that receives a BGP UPDATE message with an E-Tree Extended
Community from its peer PE, after saving the VLAN information for the
PW, MUST process it as follows (after processing procedures as
specified in Section 3.2 of [RFC4761]):
1) if the root and leaf VLAN ID in the E-Tree Extended Community
match the local root and leaf VLAN ID, then continue to 3);
2) else {
if the bit V is cleared, then {
if the PE is capable of VLAN mapping, then it MUST set
VLAN-Mapping-Mode to TRUE;
else {
Log with a message "E-Tree VLAN mapping not
supported" and exit the process;
}
if the bit V is set, and the PE is capable of VLAN mapping,
the PE with the minimum IP address MUST set VLAN-Mapping-Mode
to TRUE;
}
3) If the P bit is set {
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If the PE is a leaf-only PE itself, then forbids any traffic on
the PW;
Else the PE SHOULD set the Optimized-Mode to TRUE.
}
A PE which does not recognize this attribute SHALL ignore it silently.
If a PE has sent an E-Tree Extended Community but does not receive
any E-Tree Extended Community from its peer, the PE SHOULD then
establish a raw PW with this peer as in traditional VPLS, and set
Compatible-Mode to TRUE for this PW.
Data plane in the VPLS is the same as described in Section 4.2 of
[RFC4761], and data plane processing for a PW is the same as
described at the end of Section 6.1.
7. OAM Considerations
VPLS OAM requirements and framework as specified in [RFC6136] are
applicable to E-Tree, as both Ethernet OAM frames and data traffic
are transported over the same PW.
Ethernet OAM for E-Tree including both service OAM and segment OAM
frames SHALL undergo the same VLAN mapping as the data traffic; and
root VLAN SHOULD be applied to segment OAM frames so that they are
not filtered.
8. Applicability
The solution specified in this document is applicable to both LDP
VPLS [RFC4762] and BGP VPLS [RFC4761].
This solution is applicable to both "VPLS Only" networks and VPLS
with Ethernet aggregation networks.
This solution is also applicable to PBB VPLS networks.
9. Security Considerations
Besides security considerations as described in [RFC4448], [RFC4761]
and [RFC4762], this solution prevents leaf to leaf communication in
the data plane of VPLS when its PEs are interconnected with PWs. In
this regard, security can be enhanced for customers with this
solution.
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10. IANA Considerations
IANA allocated a value for E-Tree in the registry of Pseudowire
Interface Parameters Sub-TLV type.
Parameter ID Length Description
=======================================
0x1A 8 E-Tree
IANA allocated two new LDP status codes from the registry of name
"STATUS CODE NAME SPACE".
Range/Value E Description
------------- ----- ----------------------
0x20000003 1 E-Tree VLAN mapping not supported
0x20000004 0 Leaf to Leaf PW released
IANA allocated a value for E-Tree in the registry of BGP Extended
Community.
Type Value Sub-Type Value Name
========== ============== ============
0x80 0x0b E-Tree Info
11. References
11.1. 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 Heron,
G., "Pseudowire Setup and Maintenance Using Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC4448] Martini, L., Rosen, E., El-Aawar, N., and Heron,G.,
"Encapsulation Methods for Transport of Ethernet over MPLS
Networks", RFC 4448, April 2006.
[RFC4761] Kompella, K., and Rekhter, Y., "Virtual Private LAN Service
(VPLS) Using BGP for Auto-Discovery and Signaling", RFC
4761, January 2007.
[RFC4762] Lasserre, M. and Kompella, V., "Virtual Private LAN
Services using LDP", RFC 4762, January 2007.
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[RFC6136] Sajassi, A. and Mohan, D., "L2VPN OAM Requirements and
Framework", RFC 6136, March 2011.
11.2. Informative References
[RFC3985] Bryant, S., and Pate, P., "Pseudo Wire Emulation Edge-to-
Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC4664] Andersson, L., and Rosen, E., "Framework for Layer 2
Virtual Private Networks (L2VPNs)", RFC 4664, September
2006.
[RFC6246] Sajassi, A., Brockners, F., Mohan, D., and Serbest, Y.,
"Virtual Private LAN Service (VPLS) Interoperability with
Customer Edge (CE) Bridges", RFC 6246, June 2011.
[RFC7041] Balus, F., Sajassi, A., and Bitar, N., Extensions to VPLS
PE model for Provider Backbone Bridging, RFC 7041, November
2013.
[RFC7152] Key, R., DeLord, S., Jounay, F., Huang, L., Liu, Z., and M.
Paul, "Requirements for Metro Ethernet Forum (MEF)
Ethernet-Tree (E-Tree) Support in Layer 2 Virtual Private
Network (L2VPN)", RFC 7152, March 2014.
[RFC7387] Key, R., Yong, L., DeLord, S., Jounay, F., and Jin, L., "A
Framework for Ethernet Tree (E-Tree) Service over a
Multiprotocol Label Switching (MPLS) Network", RFC 7387,
October 2014.
[802.1Q-2011] IEEE 802.1Q, Media Access Control (MAC) Bridges and
Virtual Bridge Local Area Networks, August 2011.
[MEF4] Metro Ethernet Forum, Metro Ethernet Network Architecture
Framework - Part 1: Generic Framework, Technical
Specification MEF 4, May 2004.
[MEF6.1] Metro Ethernet Forum, "Ethernet Services Definitions -
Phase 2", Technical Specification MEF 6.1, April 2008.
[VPMS] Kamite, Y., Jounay, F., Niven-Jenkins, B., Brungard, D.,
and L. Jin, "Framework and Requirements for Virtual Private
Multicast Service (VPMS)", Work in Progress, draft-ietf-
l2vpn-vpms-frmwk-requirements-05, October 2012.
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12. Acknowledgments
The authors would like to thank Stewart Bryant for his detailed
review and suggestions, thank Adrian Farrel, Susan Hares and Shane
Amante for their valuable advices, thank Ben Mack-crane, Edwin
Mallette, Donald Fedyk, Dave Allan, Giles Heron, Raymond Key, Josh
Rogers, Sam Cao and Daniel Cohn for their valuable comments and
discussions.
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Appendix A. Other PE Models for E-Tree
A.1. A PE Model With a VSI and No bridge
If there is no bridge module in a PE, the PE may consist of Native
Service Processors (NSPs) as shown in Figure A.1 (adapted from Fig. 5
of [RFC3985]) where any transformation operation for VLANs (e.g.,
VLAN insertion/removal or VLAN mapping) may be applied. Thus a root
VLAN or leaf VLAN can be added by the NSP depending on the User
Network Interface (UNI) type (root/leaf) associated with the AC over
which the packet arrives.
Further, when a packet with a leaf VLAN exits a forwarder and arrives
at the NSP, the NSP must drop the packet if the egress AC is
associated with a leaf UNI.
Tagged PW and VLAN mapping work in the same way as in the typical PE
model.
+----------------------------------------+
| PE Device |
Multiple+----------------------------------------+
AC | | | Single | PW Instance
<------>o NSP # + PW Instance X<---------->
| | | |
|------| VSI |----------------------|
| | | Single | PW Instance
<------>o NSP #Forwarder + PW Instance X<---------->
| | | |
|------| |----------------------|
| | | Single | PW Instance
<------>o NSP # + PW Instance X<---------->
| | | |
+----------------------------------------+
Figure A.1 A PE model with a VSI and no bridge module
This PE model may be used by a Multi-Tenant Unit switch (MTU-s) in a
Hierarchical VPLS (H-VPLS) network, or a Network-facing PE (N-PE) in
an H-VPLS network with non-bridging edge devices, wherein a spoke PW
can be treated as an AC in this model.
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A.2. A PE Model With external E-Tree interface
+----------------------------------------+
| PE Device |
Root +----------------------------------------+
VLAN | | Single | PW Instance
<------>o + PW Instance X<---------->
| | |
| VSI |----------------------|
| | Single | PW Instance
| Forwarder + PW Instance X<---------->
| | |
Leaf | |----------------------|
VLAN | | Single | PW Instance
<------>o + PW Instance X<---------->
| | |
+----------------------------------------+
Figure A.2 A PE model with external E-Tree interface
A more simplified PE model is depicted in A.2, where Root/Leaf VLANs
are directly or indirectly over a single PW connected to a same VSI
forwarder in a PE, any transformation of E-Tree VLANs, e.g., VLAN
insertion/removal or VLAN mapping, can be performed by some outer
equipments, and the PE may further translate these VLANs into its own
local VLANs. This PE model may be used by an N-PE in an H-VPLS
network with bridging-capable devices, or scenarios such as providing
E-Tree Network-to-Network interfaces.
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Authors' Addresses
Yuanlong Jiang
Huawei Technologies Co., Ltd.
Bantian, Longgang district
Shenzhen 518129, China
Email: jiangyuanlong@huawei.com
Lucy Yong
Huawei USA
207 Estrella Xing
Georgetown TX, USA 78628
Email: lucyyong@huawei.com
Manuel Paul
Deutsche Telekom
Winterfeldtstr. 21
10781 Berlin, Germany
Email: manuel.paul@telekom.de
Frederic Jounay
Orange CH
4 rue caudray 1020 Renens, Switzerland
Email: frederic.jounay@orange.ch
Florin Balus
Alcatel-Lucent
701 E. Middlefield Road
Mountain View, CA, USA 94043
Email: florin.balus@alcatel-lucent.com
Wim Henderickx
Alcatel-Lucent
Copernicuslaan 50
2018 Antwerp, Belgium
Email: wim.henderickx@alcatel-lucent.com
Ali Sajassi
Cisco
170 West Tasman Drive
San Jose, CA 95134, USA
Email: sajassi@cisco.com
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