draft-ietf-l2vpn-vpls-bridge-interop-04.txt   draft-ietf-l2vpn-vpls-bridge-interop-05.txt 
Internet Working Group Ali Sajassi, Ed. Internet Working Group Ali Sajassi, Ed.
Internet Draft Frank Brockners Internet Draft Frank Brockners
Intended Status: Informational Cisco Systems Intended Status: Informational Cisco Systems
Dinesh Mohan, Ed. Dinesh Mohan, Ed.
Nortel Nortel
Yetik Serbest Yetik Serbest
Expires: May 2009 ATT
Expires: September 8, 2010 March 8, 2010
VPLS Interoperability with CE Bridges VPLS Interoperability with CE Bridges
draft-ietf-l2vpn-vpls-bridge-interop-04.txt draft-ietf-l2vpn-vpls-bridge-interop-05.txt
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draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
Abstract Abstract
One of the main motivations behind VPLS is its ability to provide One of the main motivations behind VPLS is its ability to provide
connectivity not only among customer routers and servers/hosts but connectivity not only among customer routers and servers/hosts but
also among customer IEEE bridges. VPLS is expected to deliver the also among customer IEEE bridges. VPLS is expected to deliver the
same level of service that current enterprise users are accustomed same level of service that current enterprise users are accustomed
to from their own enterprise bridged networks or their Ethernet to from their own enterprise bridged networks or their Ethernet
Service Providers. Service Providers.
When CE devices are IEEE bridges, then there are certain issues and When CE devices are IEEE bridges, then there are certain issues and
challenges that need to be accounted for in a VPLS network. The challenges that need to be accounted for in a VPLS network. The
majority of these issues have currently been addressed in the IEEE majority of these issues have been addressed in the IEEE 802.1ad
802.1ad standard for provider bridges and they can be leveraged for standard for provider bridges and they can be leveraged for VPLS
VPLS networks. This draft extends the PE model described in RFC 4664 networks. This draft extends the PE model described in [RFC-4664]
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007 based on IEEE 802.1ad bridge module, and illustrates a clear
demarcation between the IEEE bridge module and IETF LAN emulation
based on IEEE 802.1ad bridge module and illustrates a clear module. By doing so, it shows that the majority of interoperability
demarcation between IEEE bridge module and IETF LAN emulation issues with CE bridges can be delegated to the 802.1ad bridge
module. By doing so, it describes that the majority of module, thus removing the burden on the IETF LAN emulation module
interoperability issues with CE bridges can be delegated to 802.1ad
bridge module, thus removing the burden on IETF LAN emulation module
within a VPLS PE. within a VPLS PE.
Conventions Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC-2119]. document are to be interpreted as described in [RFC-2119].
Table of Contents Table of Contents
1. Introduction....................................................2 1. Introduction.................................................... 3
2. Ethernet Service Instance.......................................3 2. Ethernet Service Instance....................................... 4
3. VPLS-Capable PE Model with Bridge Module........................4 3. VPLS-Capable PE Model with Bridge Module........................ 5
4. Mandatory Issues................................................7 4. Mandatory Issues................................................ 7
4.1. Service Mapping...............................................7 4.1. Service Mapping............................................... 7
4.2. CE Bridge Protocol Handling...................................9 4.2. CE Bridge Protocol Handling................................... 9
4.3. Partial-mesh of Pseudowires..................................10 4.3. Partial-mesh of Pseudowires.................................. 10
4.4. Multicast Traffic............................................11 4.4. Multicast Traffic............................................ 11
5. Optional Issues................................................12 5. Optional Issues................................................ 12
5.1. Customer Network Topology Changes............................12 5.1. Customer Network Topology Changes............................ 12
5.2. Redundancy...................................................13 5.2. Redundancy................................................... 14
5.3. MAC Address Learning.........................................15 5.3. MAC Address Learning......................................... 15
6. Interoperability with 802.1ad Networks.........................16 6. Interoperability with 802.1ad Networks......................... 16
7. Acknowledgments................................................16 7. Acknowledgments................................................ 16
8. IANA Considerations............................................16 8. IANA Considerations............................................ 17
9. Security Considerations........................................16 draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
10. IPR Notice:...................................................17
11. Normative References..........................................17 9. Security Considerations........................................ 17
12. Informative References........................................17 10. Normative References.......................................... 17
Authors' Addresses................................................18 11. Informative References........................................ 17
Full Copyright Statement..........................................19 Authors' Addresses................................................ 18
1. Introduction 1. Introduction
Virtual Private LAN Service (VPLS) is a LAN emulation service Virtual Private LAN Service (VPLS) is a LAN emulation service
intended for providing connectivity between geographically dispersed intended for providing connectivity between geographically dispersed
customer sites across MAN/WAN (over MPLS/IP) network(s), as if they customer sites across MAN/WAN (over MPLS/IP) network(s), as if they
were connected using a LAN. One of the main motivations behind VPLS were connected using a LAN. One of the main motivations behind VPLS
is its ability to provide connectivity not only among customer is its ability to provide connectivity not only among customer
routers and servers/hosts but also among IEEE customer bridges. If routers and servers/hosts but also among IEEE customer bridges. If
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
only connectivity among customer IP routers/hosts was desired, then only connectivity among customer IP routers/hosts was desired, then
an IPLS solution [IPLS] could have been used. The strength of the an IPLS solution [IPLS] could have been used. The strength of the
VPLS solution is that it can provide connectivity to both bridge and VPLS solution is that it can provide connectivity to both bridge and
non-bridge types of CE devices. VPLS is expected to deliver the same non-bridge types of CE devices. VPLS is expected to deliver the same
level of service that current enterprise users are accustomed to level of service that current enterprise users are accustomed to
from their own enterprise bridged networks [802.1D/802.1Q] today or from their own enterprise bridged networks [802.1D/802.1Q] today or
the same level of service that they receive from their Ethernet the same level of service that they receive from their Ethernet
Service Providers using IEEE 802.1ad-based networks [P802.1ad] (or Service Providers using IEEE 802.1ad-based networks [P802.1ad] (or
its predecessor, QinQ-based network). its predecessor, QinQ-based network).
When CE devices are IEEE bridges, then there are certain issues and When CE devices are IEEE bridges, then there are certain issues and
challenges that need to be accounted for in a VPLS network. The challenges that need to be accounted for in a VPLS network. The
majority of these issues have currently been addressed in the IEEE majority of these issues have been addressed in the IEEE 802.1ad
802.1ad standard for provider bridges and they can be leveraged for standard for provider bridges and they can be leveraged for VPLS
VPLS networks. This draft extends the PE model described in RFC 4664 networks. This draft extends the PE model described in [RFC-4664]
based on IEEE 802.1ad bridge module and illustrates a clear based on IEEE 802.1ad bridge module and illustrates a clear
demarcation between IEEE bridge module and IETF LAN emulation demarcation between IEEE bridge module and IETF LAN emulation
module. By doing so, it describes that the majority of module. By doing so, it describes that the majority of
interoperability issues with CE bridges can be delegated to 802.1ad interoperability issues with CE bridges can be delegated to 802.1ad
bridge module, thus removing the burden on IETF LAN emulation module bridge module, thus removing the burden on IETF LAN emulation module
within a VPLS PE. This draft discusses these issues and wherever within a VPLS PE. This document discusses these issues and wherever
possible suggests areas to be explored in rectifying these issues. possible suggests areas to be explored in rectifying these issues.
The detailed solution specification for these issues is outside of The detailed solution specification for these issues is outside of
the scope of this document. the scope of this document.
It also discusses interoperability issues between VPLS and IEEE It also discusses interoperability issues between VPLS and IEEE
802.1ad networks when the end-to-end service spans across both types 802.1ad networks when the end-to-end service spans across both types
of networks, as outlined in [RFC-4762]. of networks, as outlined in [RFC-4762].
This draft categorizes the CE-bridge issues into two groups: 1) This draft categorizes the CE-bridge issues into two groups: 1)
Mandatory and 2) Optional. The issues in group (1) need to be Mandatory and 2) Optional. The issues in group (1) need to be
addressed in order to ensure the proper operation of CE bridges. The addressed in order to ensure the proper operation of CE bridges. The
issues in group (2) would provide additional operational improvement issues in group (2) would provide additional operational improvement
and efficiency and may not be required for interoperability with CE and efficiency and may not be required for interoperability with CE
bridges. Sections five and six discuss the mandatory and optional bridges. Sections five and six discuss the mandatory and optional
issues respectively. issues respectively.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
2. Ethernet Service Instance 2. Ethernet Service Instance
Before starting the discussion of bridging issues, it is important Before starting the discussion of bridging issues, it is important
to first clarify the Ethernet Service definition. The term VPLS has to clarify the Ethernet Service definition. The term VPLS has
different meanings in different contexts. In general, VPLS is used different meanings in different contexts. In general, VPLS is used
in the following contexts [Eth-OAM]: a) as an end-to-end bridged-LAN in the following contexts [Eth-OAM]: a) as an end-to-end bridged-LAN
service over one or more network (one of which being MPLS/IP service over one or more network (one of which being MPLS/IP
network), b) as an MPLS/IP network supporting these bridged LAN network), b) as an MPLS/IP network supporting these bridged LAN
services, and c) as (V)LAN emulation. For better clarity, we services, and c) as (V)LAN emulation. For better clarity, we
differentiate between its usage as network versus service by using differentiate between its usage as network versus service by using
the terms VPLS network and VPLS instance respectively. Furthermore, the terms VPLS network and VPLS instance respectively. Furthermore,
we confine VPLS (both network and service) to only the portion of we confine VPLS (both network and service) to only the portion of
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
the end-to-end network that spans across an MPLS/IP network. For an the end-to-end network that spans across an MPLS/IP network. For an
end-to-end service (among different sites of a given customer), we end-to-end service (among different sites of a given customer), we
use the term "Ethernet Service Instance" or ESI. use the term "Ethernet Service Instance" or ESI.
[MFA-Ether] defines the Ethernet Service Instance (ESI) as an [MFA-Ether] defines the Ethernet Service Instance (ESI) as an
association of two or more Attachment Circuits (ACs) over which an association of two or more Attachment Circuits (ACs) over which an
Ethernet service is offered to a given customer. An AC can be either Ethernet service is offered to a given customer. An AC can be either
a UNI or a NNI; furthermore, it can be an Ethernet interface or a a UNI or a NNI; furthermore, it can be an Ethernet interface or a
VLAN, it can be an ATM or FR VC, or it can be a PPP/HDLC interface. VLAN, it can be an ATM or FR VC, or it can be a PPP/HDLC interface.
If an ESI is associated with more than two ACs, then it is a If an ESI is associated with more than two ACs, then it is a
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domains. domains.
An ESI most often represents a customer or a specific service An ESI most often represents a customer or a specific service
requested by a customer. Since traffic isolation among different requested by a customer. Since traffic isolation among different
customers (or their associated services) is of paramount importance customers (or their associated services) is of paramount importance
in service provider networks, its realization shall be done such in service provider networks, its realization shall be done such
that it provides a separate MAC address domain and broadcast domain that it provides a separate MAC address domain and broadcast domain
per ESI. A separate MAC address domain is provided by using a per ESI. A separate MAC address domain is provided by using a
separate filtering database (e.g., FIB) per ESI (for both VPLS and separate filtering database (e.g., FIB) per ESI (for both VPLS and
IEEE 802.1ad networks) and separate broadcast domain is provided by IEEE 802.1ad networks) and separate broadcast domain is provided by
using a full-mesh of PWs per ESI over the IP/MPLS core in a VPLS using a full-mesh of pseudowires per ESI over the IP/MPLS core in a
network and/or a dedicated Service VLAN per ESI in an IEEE 802.1ad VPLS network and/or a dedicated Service VLAN per ESI in an IEEE
network. 802.1ad network.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
3. VPLS-Capable PE Model with Bridge Module 3. VPLS-Capable PE Model with Bridge Module
[RFC-4664] defines three models for VPLS-capable PE (VPLS-PE) based [RFC-4664] defines three models for VPLS-capable PE (VPLS-PE) based
on the bridging functionality that needs to be supported by the PE. on the bridging functionality that needs to be supported by the PE.
If the CE devices can include both routers/hosts and IEEE bridges, If the CE devices can be routers/hosts or IEEE bridges, the second
then the second model is the most suitable and adequate one and it model from [RFC-4664] is the most suitable, and it is both adequate
is consistent with IEEE standards for Provider Bridges [P802.1ad]. to provide the VPLS level of service and consistent with the IEEE
We briefly describe the second model and then expand upon this model standards for Provider Bridges [P802.1ad]. We briefly describe the
to show its sub-components based on [P802.1ad] Provider Bridge second model and then expand upon this model to show its sub-
model. components based on [P802.1ad] Provider Bridge model.
As described in [RFC-4664], the second model for VPLS-PE contains a As described in [RFC-4664], the second model for VPLS-PE contains a
single bridge module supporting all the VPLS instances on that PE single bridge module supporting all the VPLS instances on that PE
where each VPLS instance is represented by a unique VLAN inside that where each VPLS instance is represented by a unique VLAN inside that
bridge module (also known as Service VLAN or S-VLAN). The bridge bridge module (also known as Service VLAN or S-VLAN). The bridge
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007 module has a single "Emulated LAN" interface over which it
communicates with all VPLS forwarders and each VPLS instance is
module has a single "Emulated LAN" interface over which each VPLS represented by a unique S-VLAN tag. Each VPLS instance can consist
instance is represented by a unique S-VLAN tag. Each VPLS instance of a set of pseudowires and its associated forwarder corresponding
can consist of a set of PWs and its associated forwarder to a single Virtual LAN (VLAN) as depicted in Figure 1 below. Thus,
corresponding to a single Virtual LAN (VLAN) as depicted in Figure 1 sometimes it is referred to as VLAN emulation.
below. Thus, sometimes it is referred to as VLAN emulation.
+----------------------------------------+ +----------------------------------------+
| VPLS-capable PE model | | VPLS-capable PE model |
| +---------------+ +------+ | | +---------------+ +------+ |
| | | |VPLS-1|------------ | | | |VPLS-1|------------
| | |==========|Fwdr |------------ PWs | | |=======+ |Fwdr |------------ PWs
| | Bridge ------------ |------------ | | Bridge --------|--- |------------
| | | S-VLAN-1 +------+ | | | | SVID-1| +------+ |
| | Module | o | | | Module | | o |
| | | o | | | | | o |
| | (802.1ad | o | | | (802.1ad | | o |
| | bridge) | o | | | bridge) | | o |
| | | o | | | | | o |
| | | S-VLAN-n +------+ | | | | SVID-n| +------+ |
| | ------------VPLS-n|------------- | | --------|---VPLS-n|-------------
| | |==========| Fwdr |------------- PWs | | |=======+ | Fwdr |------------- PWs
| | | ^ | |------------- | | | ^ | |-------------
| +---------------+ | +------+ | | +---------------+ | +------+ |
| | | | | |
+-------------------------|--------------+ +-----------------------|----------------+
LAN emulation Interface |
LAN emulation (multi-access) Interface
Figure 1. VPLS-capable PE Model Figure 1. VPLS-capable PE Model
Customer frames associated with a given ESI, carry the S-VLAN ID for Customer frames associated with a given ESI, carry the S-VLAN ID for
that ESI over the LAN emulation interface. The S-VLAN ID is stripped that ESI over the LAN emulation interface. The S-VLAN ID is stripped
before transmitting the frames over the set of PWs associated with draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
that VPLS instance (assuming raw mode PWs are used as specified in
[RFC-4448]). before transmitting the frames over the set of pseudowires
associated with that VPLS instance (assuming raw mode PWs are used
as specified in [RFC-4448]).
The bridge module can itself consist of one or two sub-components The bridge module can itself consist of one or two sub-components
depending on the functionality that it needs to perform. The depending on the functionality that it needs to perform. The
following Figure 2 depicts the model for the bridge module based on following Figure 2 depicts the model for the bridge module based on
[P802.1ad]. [P802.1ad].
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
+-------------------------------+ +-------------------------------+
| 802.1ad Bridge Module Model | | 802.1ad Bridge Module Model |
| | | |
+---+ | +------+ +-----------+ | +---+ | +------+ +-----------+ |
|CE |---------|C-VLAN|------| | | |CE |---------|C-VLAN|------| | |
+---+ | |bridge|------| | | +---+ | |bridge|------| | |
| +------+ | | | | +------+ | | |
| o | S-VLAN | | | o | S-VLAN | |
| o | | | | o | | |
| o | Bridge | | | o | Bridge | |
skipping to change at page 6, line 46 skipping to change at page 7, line 4
such as RSTP and MSTP. The reason that such participation is such as RSTP and MSTP. The reason that such participation is
required is because a customer VLAN (C-VLAN) at one site can be required is because a customer VLAN (C-VLAN) at one site can be
mapped into a different C-VLAN at a different site or in case of mapped into a different C-VLAN at a different site or in case of
asymmetric mapping, a customer Ethernet port at one site can be asymmetric mapping, a customer Ethernet port at one site can be
mapped into a customer VLAN (or group of C-VLANs) at a different mapped into a customer VLAN (or group of C-VLANs) at a different
site. site.
The C-VLAN bridge component does service selection and The C-VLAN bridge component does service selection and
identification based on C-VLAN tags. Each frame from the customer identification based on C-VLAN tags. Each frame from the customer
device is assigned to a C-VLAN and presented at one or more internal device is assigned to a C-VLAN and presented at one or more internal
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
port-based interfaces, each supporting a single service instance port-based interfaces, each supporting a single service instance
that the customer desires to carry that C-VLAN. Similarly frames that the customer desires to carry that C-VLAN. Similarly frames
from the provider network are assigned to an internal interface or from the provider network are assigned to an internal interface or
'LAN' (e.g, between C-VLAN and S-VLAN components) on the basis of 'LAN' (e.g, between C-VLAN and S-VLAN components) on the basis of
the S-VLAN tag. Since each internal interface supports a single the S-VLAN tag. Since each internal interface supports a single
service instance, the S-VLAN tag can be, and is, removed at this service instance, the S-VLAN tag can be, and is, removed at this
interface by the S-VLAN bridge component. If multiple C-VLANs are interface by the S-VLAN bridge component. If multiple C-VLANs are
supported by this service instance (e.g., VLAN bundling or port- supported by this service instance (e.g., VLAN bundling or port-
based), then the frames will have already been tagged with C-VLAN based), then the frames will have already been tagged with C-VLAN
tags. If a single C-VLAN is supported by this service instance tags. If a single C-VLAN is supported by this service instance
(e.g., VLAN-based), then the frames will not have been tagged with (e.g., VLAN-based), then the frames will not have been tagged with a
C-VLAN tag since C-VLAN can be derived from the S-VLAN (e.g., one to C-VLAN tag since C-VLAN can be derived from the S-VLAN (e.g., one to
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
one mapping). The C-VLAN aware bridge component applies a port VLAN one mapping). The C-VLAN aware bridge component applies a port VLAN
ID (PVID) to untagged frames received on each internal 'LAN', ID (PVID) to untagged frames received on each internal 'LAN',
allowing full control over the delivery of frames for each C-VLAN allowing full control over the delivery of frames for each C-VLAN
through the Customer UNI Port. through the Customer UNI Port.
4. Mandatory Issues 4. Mandatory Issues
4.1. Service Mapping 4.1. Service Mapping
Different Ethernet AC types can be associated with a single Ethernet Different Ethernet AC types can be associated with a single Ethernet
skipping to change at page 7, line 44 skipping to change at page 8, line 4
capabilities in terms of customer ACs mapping to the customer capabilities in terms of customer ACs mapping to the customer
service instance. service instance.
The following table lists possible mappings that can exist between The following table lists possible mappings that can exist between
customer ACs and its associated ESI - this table is extracted from customer ACs and its associated ESI - this table is extracted from
[MFA-Ether]. As it can be seen, there are several possible ways to [MFA-Ether]. As it can be seen, there are several possible ways to
perform such mapping. In the first scenario, it is assumed that an perform such mapping. In the first scenario, it is assumed that an
Ethernet physical port only carries untagged traffic and all the Ethernet physical port only carries untagged traffic and all the
traffic is mapped to the corresponding service instance or ESI. This traffic is mapped to the corresponding service instance or ESI. This
is referred to as "port-based with untagged traffic". In the second is referred to as "port-based with untagged traffic". In the second
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
scenario, it is assumed that an Ethernet physical port carries both scenario, it is assumed that an Ethernet physical port carries both
tagged and untagged traffic and all that traffic is mapped to the tagged and untagged traffic and all that traffic is mapped to the
corresponding service instance or ESI. This is referred to as "port- corresponding service instance or ESI. This is referred to as "port-
based with tagged and untagged traffic". In the third scenario, it based with tagged and untagged traffic". In the third scenario, it
is assumed that only a single VLAN is mapped to the corresponding is assumed that only a single VLAN is mapped to the corresponding
service instance or ESI (referred to as VLAN-based). Finally, in the service instance or ESI (referred to as VLAN-based). Finally, in the
fourth scenario, it is assumed that a group of VLANs from the fourth scenario, it is assumed that a group of VLANs from the
Ethernet physical interface is mapped to the corresponding service Ethernet physical interface is mapped to the corresponding service
instance or ESI. instance or ESI.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
=================================================================== ===================================================================
Ethernet I/F & Associated Service Instance(s) Ethernet I/F & Associated Service Instance(s)
------------------------------------------------------------------- -------------------------------------------------------------------
Port-based Port-based VLAN-based VLAN Port-based Port-based VLAN-based VLAN
untagged tagged & bundling untagged tagged & bundling
untagged untagged
------------------------------------------------------------------- -------------------------------------------------------------------
Port-based Y N Y(Note-1) N Port-based Y N Y(Note-1) N
untagged untagged
skipping to change at page 8, line 44 skipping to change at page 9, line 5
two tags; where the outer tag is S-VLAN and the inner tag is C-VLAN two tags; where the outer tag is S-VLAN and the inner tag is C-VLAN
received from "port-based" AC. One application example for such CE received from "port-based" AC. One application example for such CE
device is in a BRAS for DSL aggregation over Metro Ethernet network. device is in a BRAS for DSL aggregation over Metro Ethernet network.
Note-3: In this asymmetric mapping scenario, it is assumed that the Note-3: In this asymmetric mapping scenario, it is assumed that the
CE device with "VLAN-based" AC can support the [P802.1ad] frame CE device with "VLAN-based" AC can support the [P802.1ad] frame
format because it will receive Ethernet frames with two tags; where format because it will receive Ethernet frames with two tags; where
the outer tag is S-VLAN and the inner tag is C-VLAN received from the outer tag is S-VLAN and the inner tag is C-VLAN received from
"VLAN bundling" AC. "VLAN bundling" AC.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
If a PE uses an S-VLAN tag for a given ESI (either by adding an S- If a PE uses an S-VLAN tag for a given ESI (either by adding an S-
VLAN tag to customer traffic or by replacing a C-VLAN tag with a S- VLAN tag to customer traffic or by replacing a C-VLAN tag with a S-
VLAN tag), then the frame format and EtherType for S-VLAN shall VLAN tag), then the frame format and EtherType for S-VLAN shall
adhere to [P802.1ad]. adhere to [P802.1ad].
As mentioned before, the mapping function between the customer AC As mentioned before, the mapping function between the customer AC
and its associated ESI is a local function and thus when the AC is a and its associated ESI is a local function and thus when the AC is a
single customer VLAN, it is possible to map different customer VLANs single customer VLAN, it is possible to map different customer VLANs
at different sites to a single ESI without coordination among those at different sites to a single ESI without coordination among those
sites. sites.
When a port-based mapping or a VLAN-bundling mapping is used, then When a port-based mapping or a VLAN-bundling mapping is used, then
the PE may use an additional S-VLAN tag to mark the customer traffic the PE may use an additional S-VLAN tag to mark the customer traffic
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
received over that AC as belonging to a given ESI. If the PE uses received over that AC as belonging to a given ESI. If the PE uses
the additional S-VLAN tag, then in the opposite direction the PE the additional S-VLAN tag, then in the opposite direction the PE
shall strip the S-VLAN tag before sending the customer frames over shall strip the S-VLAN tag before sending the customer frames over
the same AC. However, when VLAN-mapping mode is used at an AC and if the same AC. However, when VLAN-mapping mode is used at an AC and if
the PE uses S-VLAN tag locally, then if the Ethernet interface is a the PE uses S-VLAN tag locally, then if the Ethernet interface is a
UNI, the tagged frames over this interface shall have a frame format UNI, the tagged frames over this interface shall have a frame format
based on [802.1Q] and the PE shall translate the customer tag (C- based on [802.1Q] and the PE shall translate the customer tag (C-
VLAN) into the provider tag (S-VLAN) upon receiving a frame from the VLAN) into the provider tag (S-VLAN) upon receiving a frame from the
customer and in the opposite direction, the PE shall translate from customer and in the opposite direction, the PE shall translate from
provider frame format (802.1ad) back to customer frame format provider frame format (802.1ad) back to customer frame format
skipping to change at page 9, line 33 skipping to change at page 9, line 47
When a VPLS-capable PE is connected to a CE bridge, then depending When a VPLS-capable PE is connected to a CE bridge, then depending
on the type of Attachment Circuit, different protocol handling may on the type of Attachment Circuit, different protocol handling may
be required by the bridge module of the PE. [P802.1ad] states that be required by the bridge module of the PE. [P802.1ad] states that
when a PE is connected to a CE bridge, then the service offered by when a PE is connected to a CE bridge, then the service offered by
the PE may appear to specific customer protocols running on the CE the PE may appear to specific customer protocols running on the CE
in one of the four ways: in one of the four ways:
i) Transparent to the operation of the protocol among CEs of i) Transparent to the operation of the protocol among CEs of
different sites using the service provided, appearing as an different sites using the service provided, appearing as an
individual LAN without bridges; or, individual LAN without bridges; or,
ii) Discarding frames, acting as a non-participating barrier to the i i) Discarding frames, acting as a non-participating barrier to the
operation of the protocol; or, operation of the protocol; or,
iii) Peering, with a local protocol entity at the point of provider i i i) Peering, with a local protocol entity at the point of provider
ingress and egress, participating in and terminating the ingress and egress, participating in and terminating the
operation of the protocol; or, operation of the protocol; or,
iv) Participation in individual instances of customer protocols. iv) Participation in individual instances of customer protocols.
All the above CE bridge protocol handling can be supported via the All the above CE bridge protocol handling can be supported via the
PE model with the bridge module depicted in figure-2 (based on PE model with the bridge module depicted in figure-2 (based on
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
[802.1ad]). For example, when an Attachment Circuit is port-based, [802.1ad]). For example, when an Attachment Circuit is port-based,
then the bridge module of the PE can operate transparently with then the bridge module of the PE can operate transparently with
respect to the CE's RSTP/MSTP protocols (and thus no C-VLAN respect to the CE's RSTP/MSTP protocols (and thus no C-VLAN
component is required for that customer UNI). However, when an component is required for that customer UNI). However, when an
Attachment Circuit is VLAN-based (either VLAN-based or VLAN Attachment Circuit is VLAN-based (either VLAN-based or VLAN
bundling), then the bridge module of the PE needs to peer with the bundling), then the bridge module of the PE needs to peer with the
RSTP/MSTP protocols running on the CE (and thus the C-VLAN bridge RSTP/MSTP protocols running on the CE (and thus the C-VLAN bridge
component is required). In other words, when the AC is VLAN-based, component is required). In other words, when the AC is VLAN-based,
then protocol peering between CE and PE devices may be needed. There then protocol peering between CE and PE devices may be needed. There
are also protocols that require peering but are independent from the are also protocols that require peering but are independent from the
type of Attachment Circuit. An example of such protocol is the link type of Attachment Circuit. An example of such protocol is the link
aggregation protocol [802.3ad]; however, this is a media-dependent aggregation protocol [802.3ad]; however, this is a media-dependent
protocol as its name implies. protocol as its name implies.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
[P802.1ad] reserves a block of 16 MAC addresses for the operation of [P802.1ad] reserves a block of 16 MAC addresses for the operation of
C-VLAN and S-VLAN bridge components and it shows which of these C-VLAN and S-VLAN bridge components and it shows which of these
reserved MAC addresses are only for C-VLAN bridge component and reserved MAC addresses are only for C-VLAN bridge component and
which ones are only for S-VLAN bridge component and which ones apply which ones are only for S-VLAN bridge component and which ones apply
to both C-VLAN and S-VLAN components. to both C-VLAN and S-VLAN components.
4.3. Partial-mesh of Pseudowires 4.3. Partial-mesh of Pseudowires
A PW failure results in creation of partial-mesh in a VPLS service A VPLS service depends on a full mesh of pseudowires, so a
with adverse effects. If the CE devices belonging to an ESI are pseudowire failure reduces the underlying connectivity to a partial
routers running link state routing protocols that use LAN procedures mesh and this can have adverse effects on the VPLS service. If the
over that ESI, then a partial-mesh of PWs can result in "black CE devices belonging to an ESI are routers running link state
holing" traffic among the selected set of routers. And if the CE routing protocols that use LAN procedures over that ESI, then a
devices belonging to an ESI are IEEE bridges, then a partial-mesh of partial-mesh of PWs can result in "black holing" traffic among the
PWs can cause broadcast storms in the customer and provider selected set of routers. And if the CE devices belonging to an ESI
networks. Furthermore, it can cause multiple copies of a single are IEEE bridges, then a partial-mesh of PWs can cause broadcast
frame to be received by the CE and/or PE devices. Therefore, it is storms in the customer and provider networks. Furthermore, it can
of paramount importance to be able to detect PW failure and to take cause multiple copies of a single frame to be received by the CE
corrective action to prevent creation of partial-mesh of PWs. and/or PE devices. Therefore, it is of paramount importance to be
able to detect PW failure and to take corrective action to prevent
creation of partial-mesh of PWs.
One option is to define a procedure for detection of partial mesh in One option is to define a procedure for detection of partial mesh in
which each PE keeps track of the status of PW Endpoint Entities (EEs which each PE keeps track of the status of PW Endpoint Entities (EEs
- e.g., VPLS forwarders) for itself as well as the ones reported by - e.g., VPLS forwarders) for itself as well as the ones reported by
other PEs. Therefore, upon a PW failure, the PE that detects the other PEs. Therefore, upon a PW failure, the PE that detects the
failure not only takes notice locally but it notifies other PEs failure not only takes notice locally but it notifies other PEs
belonging to that service instance of such failure so that all the belonging to that service instance of such failure so that all the
participant PEs have a consistent view of the PW mesh. Such a participant PEs have a consistent view of the PW mesh. Such a
procedure is for the detection of partial mesh per service instance procedure is for the detection of partial mesh per service instance
and in turn it relies on additional procedure for PW failure and in turn it relies on additional procedure for PW failure
detection such as BFD or VCCV. Given that there can be tens (or even detection such as BFD or VCCV. Given that there can be tens (or even
hundreds) of thousands of PWs in a PE, there can be scalability hundreds) of thousands of PWs in a PE, there can be scalability
issues with such fault detection/notification procedures. issues with such fault detection/notification procedures.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
However, if the PE model as depicted in Figure 2, is used, then However, if the PE model as depicted in Figure 2, is used, then
[P802.1ag] procedures could be used for detection of partial-mesh of [P802.1ag] procedures could be used for detection of partial-mesh of
PWs. [p802.1ag] defines a set of procedures for fault detection, PWs. [p802.1ag] defines a set of procedures for fault detection,
verification, isolation, and notification per ESI. verification, isolation, and notification per ESI.
The fault detection mechanism of [p8021.ag] can be used to perform The fault detection mechanism of [p8021.ag] can be used to perform
connectivity check among PEs belonging to a given VPLS instance. It connectivity check among PEs belonging to a given VPLS instance. It
checks the integrity of a service instance end-to-end within an checks the integrity of a service instance end-to-end within an
administrative domain - e.g., from one AC at one end of the network administrative domain - e.g., from one AC at one end of the network
to another AC at the other end of the network. Therefore, its path to another AC at the other end of the network. Therefore, its path
coverage includes bridge module within a PE and it is not limited to coverage includes bridge module within a PE and it is not limited to
just PWs. Furthermore, [P802.1ag] operates transparently over the just PWs. Furthermore, [P802.1ag] operates transparently over the
full-mesh of PWs for a given service instance since it operates at full-mesh of PWs for a given service instance since it operates at
the Ethernet level (and not at PW level). It should be noted that the Ethernet level (and not at PW level). It should be noted that
[P802.1ag] assumes that the Ethernet links or LAN segments [P802.1ag] assumes that the Ethernet links or LAN segments
connecting provider bridges are full-duplex and the failure in one connecting provider bridges are full-duplex and the failure in one
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
direction results in the failure of the whole link or LAN segment. direction results in the failure of the whole link or LAN segment.
However, that is not the case for VPLS instance since a PW consists However, that is not the case for VPLS instance since a PW consists
of two uni-directional LSPs and one direction can fail independently of two uni-directional LSPs and one direction can fail independently
of the other causing an inconsistent view of the full-mesh by the of the other causing an inconsistent view of the full-mesh by the
participating PEs till the detected failure in one side is participating PEs till the detected failure in one side is
propagated to the other side. propagated to the other side.
4.4. Multicast Traffic 4.4. Multicast Traffic
VPLS follows a centralized model for multicast replication within an VPLS follows a centralized model for multicast replication within an
skipping to change at page 11, line 40 skipping to change at page 12, line 4
a VPLS network, is to include the use of IGMP snooping in order to a VPLS network, is to include the use of IGMP snooping in order to
send the packet only to the PEs that have receivers for that send the packet only to the PEs that have receivers for that
traffic, rather than to all the PEs in the VPLS instance. If the traffic, rather than to all the PEs in the VPLS instance. If the
customer bridge or its network has dual-home connectivity, then for customer bridge or its network has dual-home connectivity, then for
proper operation of IGMP snooping, the PE must generate a "General proper operation of IGMP snooping, the PE must generate a "General
Query" over that customer's UNIs upon receiving a customer topology Query" over that customer's UNIs upon receiving a customer topology
change notification as described in Section 7 of [RFC-4541]. A change notification as described in Section 7 of [RFC-4541]. A
"General Query" by the PE results in proper registration of the "General Query" by the PE results in proper registration of the
customer multicast MAC address(s) at the PE when there is customer customer multicast MAC address(s) at the PE when there is customer
topology change. It should be noted that IGMP snooping provides a topology change. It should be noted that IGMP snooping provides a
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
solution for IP multicast packets and is not applicable to general solution for IP multicast packets and is not applicable to general
multicast data. multicast data.
Using the IGMP-snooping as described, the ingress PE can select a Using the IGMP-snooping as described, the ingress PE can select a
sub-set of PWs for packet replication; therefore, avoiding sending sub-set of PWs for packet replication; therefore, avoiding sending
multicast packets to the egress PEs that don't need them. However, multicast packets to the egress PEs that don't need them. However,
the replication is still performed by the ingress PE. In order to the replication is still performed by the ingress PE. In order to
avoid, replication at the ingress PE, one may want to use multicast avoid, replication at the ingress PE, one may want to use multicast
distribution trees (MDTs) in the provider core network; however, distribution trees (MDTs) in the provider core network; however,
this brings with it some potential pitfalls. If the MDT is used for this brings with it some potential pitfalls. If the MDT is used for
all multicast traffic of a given customer, then this results in all multicast traffic of a given customer, then this results in
customer multicast and unicast traffic being forwarded on different customer multicast and unicast traffic being forwarded on different
PWs and even on a different physical topology within the provider PWs and even on a different physical topology within the provider
network. This is a serious issue for customer bridges because network. This is a serious issue for customer bridges because
customer BPDUs, which are multicast data, can take a different path customer BPDUs, which are multicast data, can take a different path
through the network than the unicast data. Situations might arise through the network than the unicast data. Situations might arise
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
where either unicast OR multicast connectivity is lost. If unicast where either unicast OR multicast connectivity is lost. If unicast
connectivity is lost, but multicast forwarding continues to work, connectivity is lost, but multicast forwarding continues to work,
the customer spanning tree would not take notice which results in the customer spanning tree would not take notice which results in
loss of its unicast traffic. Similarly, if multicast connectivity is loss of its unicast traffic. Similarly, if multicast connectivity is
lost, but unicast is working, then the customer spanning tree will lost, but unicast is working, then the customer spanning tree will
activate the blocked port which may result in a loop within the activate the blocked port which may result in a loop within the
customer network. Therefore, the MDT cannot be used for both customer network. Therefore, the MDT cannot be used for both
customer multicast control and data traffic. If it is used, it customer multicast control and data traffic. If it is used, it
should only be limited to customer data traffic. However, there can should only be limited to customer data traffic. However, there can
be a potential issue even when it is used for customer data traffic be a potential issue even when it is used for customer data traffic
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A single CE or a customer network can be connected to a provider A single CE or a customer network can be connected to a provider
network using more than one User-Network Interface (UNI). network using more than one User-Network Interface (UNI).
Furthermore, a single CE or a customer network can be connected to Furthermore, a single CE or a customer network can be connected to
more than one provider network. [RFC-4665] provides some examples of more than one provider network. [RFC-4665] provides some examples of
such customer network connectivity that are depicted in Figure 3 such customer network connectivity that are depicted in Figure 3
below. Such network topologies are designed to protect against the below. Such network topologies are designed to protect against the
failure or removal of network components from the customer network failure or removal of network components from the customer network
and it is assumed that the customer leverages the spanning tree and it is assumed that the customer leverages the spanning tree
protocol to protect against these cases. Therefore, in such protocol to protect against these cases. Therefore, in such
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
scenarios, it is important to flush customer MAC addresses in the scenarios, it is important to flush customer MAC addresses in the
provider network upon the customer topology change to avoid black provider network upon the customer topology change to avoid black
holing of customer frames. holing of customer frames.
+----------- +--------------- +----------- +---------------
| | | |
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
| CE |-----| PE | | CE |-----| PE | | CE |-----| PE | | CE |-----| PE |
|device| |device| |device| |device| SP network |device| |device| |device| |device| SP network
+------+\ +------+ +------+\ +------+ +------+\ +------+ +------+\ +------+
| \ | | \ | | \ | | \ |
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
|Back \ | |Back \ +--------------- |Back \ | |Back \ +---------------
|door \ | SP network |door \ +--------------- |door \ | SP network |door \ +---------------
|link \ | |link \ | |link \ | |link \ |
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
| CE | | PE | | CE | | PE | | CE | | PE | | CE | | PE |
|device|-----|device| |device|-----|device| SP network |device|-----|device| |device|-----|device| SP network
+------+ +------+ +------+ +------+ +------+ +------+ +------+ +------+
| | | |
+------------ +--------------- +------------ +---------------
(a) (b) (a) (b)
skipping to change at page 13, line 44 skipping to change at page 14, line 5
To address this issue, [P802.1ad] requires that customer topology To address this issue, [P802.1ad] requires that customer topology
change notification to be detected at the ingress of the S-VLAN change notification to be detected at the ingress of the S-VLAN
bridge component and the S-VLAN bridge transmits a Customer Change bridge component and the S-VLAN bridge transmits a Customer Change
Notification (CCN) message with the S-VLAN ID associated with that Notification (CCN) message with the S-VLAN ID associated with that
service instance and a destination MAC address as specified in the service instance and a destination MAC address as specified in the
block of 16 reserved multicast MAC addresses. Upon receiving the block of 16 reserved multicast MAC addresses. Upon receiving the
CCN, the provider bridge will flush all the customer MAC addresses CCN, the provider bridge will flush all the customer MAC addresses
associated with that S-VLAN ID on all the provider bridge interfaces associated with that S-VLAN ID on all the provider bridge interfaces
except the one that the CCN message is received from. except the one that the CCN message is received from.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
Based on the provider bridge model depicted in Figure 1, there are Based on the provider bridge model depicted in Figure 1, there are
two methods of propagating the CCN message over the VPLS network. two methods of propagating the CCN message over the VPLS network.
The first method is to translate the in-band CCN message into an The first method is to translate the in-band CCN message into an
out-of-band "MAC Address Withdrawal" message as specified in [RFC- out-of-band "MAC Address Withdrawal" message as specified in [RFC-
4762] and the second method is to treat the CCN message as customer 4762] and the second method is to treat the CCN message as customer
data and pass it transparently over the set of PWs associated with data and pass it transparently over the set of PWs associated with
that VPLS instance. The second method is recommended because of ease that VPLS instance. The second method is recommended because of ease
of interoperability between the bridge and the LAN emulation modules of interoperability between the bridge and the LAN emulation modules
of the PE. of the PE.
5.2. Redundancy 5.2. Redundancy
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
[RFC-4762] talks about dual-homing of a given u-PE to two n-PEs over [RFC-4762] talks about dual-homing of a given u-PE to two n-PEs over
a provider MPLS access network to provide protection against link a provider MPLS access network to provide protection against link
and node failure - e.g., in case the primary n-PE fails or the and node failure - e.g., in case the primary n-PE fails or the
connection to it fails, then the u-PE uses the backup PWs to reroute connection to it fails, then the u-PE uses the backup PWs to reroute
the traffic to the backup n-PE. Furthermore, it discusses the the traffic to the backup n-PE. Furthermore, it discusses the
provision of redundancy when a provider Ethernet access network is provision of redundancy when a provider Ethernet access network is
used and how any arbitrary access network topology (not just limited used and how any arbitrary access network topology (not just limited
to hub-and-spoke) can be supported using the provider's MSTP to hub-and-spoke) can be supported using the provider's MSTP
protocol and how the provider MSTP for a given access network can be protocol and how the provider MSTP for a given access network can be
confined to that access network and operate independently from MSTP confined to that access network and operate independently from MSTP
protocols running in other access networks. protocols running in other access networks.
In both types of redundancy mechanisms (Ethernet versus MPLS access In both types of redundancy mechanism (Ethernet versus MPLS access
networks), only one n-PE is active for a given VPLS instance at any networks), only one n-PE is active for a given VPLS instance at any
time. In case of an Ethernet access network, core-facing PWs (for a time. In case of an Ethernet access network, core-facing PWs (for a
VPLS instance) at the n-PE are blocked by the MSTP protocol; VPLS instance) at the n-PE are blocked by the MSTP protocol;
whereas, in case of a MPLS access network, the access-facing PW is whereas, in case of a MPLS access network, the access-facing PW is
blocked at the u-PE for a given VPLS instance. blocked at the u-PE for a given VPLS instance.
-------------------------+ Provider +------------------------- -------------------------+ Provider +-----------------------
. Core . . Core .
+------+ . . +------+ +------+ . . +------+
| n-PE |======================| n-PE | | n-PE |======================| n-PE |
Provider | (P) |---------\ /-------| (P) | Provider Provider | (P) |---------\ /-------| (P) | Provider
Access +------+ ._ \ / . +------+ Access Access +------+ ._ \ / . +------+ Access
Network . \/ . Network Network . \/ . Network
(1) +------+ . /\ . +------+ (2) (1) +------+ . /\ . +------+ (2)
| n-PE |----------/ \--------| n-PE | | n-PE |----------/ \--------| n-PE |
| (B) |----------------------| (B) |_ | (B) |----------------------| (B) |_
+------+ . . +------+ +------+ . . +------+
. . . .
------------------------+ +------------------------- ------------------------+ +-----------------------
Figure 4. Bridge Module Model Figure 4. Bridge Module Model
Figure 4 shows two provider access networks each with two n-PEs Figure 4 shows two provider access networks each with two n-PEs
where the n-PEs are connected via a full mesh of PWs for a given where the n-PEs are connected via a full mesh of PWs for a given
VPLS instance. As shown in the figure, only one n-PE in each access VPLS instance. As shown in the figure, only one n-PE in each access
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
network is serving as a Primary PE (P) for that VPLS instance and network is serving as a Primary PE (P) for that VPLS instance and
the other n-PE is serving as the backup PE (B). In this figure, each the other n-PE is serving as the backup PE (B). In this figure, each
primary PE has two active PWs originating from it. Therefore, when a primary PE has two active PWs originating from it. Therefore, when a
multicast, broadcast, and unknown unicast frame arrives at the multicast, broadcast, and unknown unicast frame arrives at the
primary n-PE from the access network side, the n-PE replicates the primary n-PE from the access network side, the n-PE replicates the
frame over both PWs in the core even though it only needs to send frame over both PWs in the core even though it only needs to send
the frames over a single PW (shown with "==" in Figure 4) to the the frames over a single PW (shown with "==" in Figure 4) to the
primary n-PE on the other side. This is an unnecessary replication primary n-PE on the other side. This is an unnecessary replication
of the customer frames that consumes core-network bandwidth (half of of the customer frames that consumes core-network bandwidth (half of
the frames get discarded at the receiving n-PE). This issue gets the frames get discarded at the receiving n-PE). This issue gets
aggravated when there are more than two n-PEs per provider access aggravated when there are more than two n-PEs per provider access
network - e.g., if there are three n-PEs or four n-PEs per access network - e.g., if there are three n-PEs or four n-PEs per access
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
network, then 67% or 75% of core-BW for multicast, broadcast and network, then 67% or 75% of core-BW for multicast, broadcast and
unknown unicast are respectively wasted. unknown unicast are respectively wasted.
Therefore, it is recommended to have a protocol among n-PEs that can Therefore, it is recommended to have a protocol among n-PEs that can
disseminate the status of PWs (active or blocked) among themselves disseminate the status of PWs (active or blocked) among themselves
and furthermore to have it tied up with the redundancy mechanism and furthermore to have it tied up with the redundancy mechanism
such that per VPLS instance the status of active/backup n-PE gets such that per VPLS instance the status of active/backup n-PE gets
reflected on the corresponding PWs emanating from that n-PE. reflected on the corresponding PWs emanating from that n-PE.
The above discussion was centered on the lack of efficiency with The above discussion was centered on the lack of efficiency with
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number of MAC addresses per customer sites is very limited (most number of MAC addresses per customer sites is very limited (most
often one MAC address per CE). However, when CEs are bridges, then often one MAC address per CE). However, when CEs are bridges, then
there can be many customer MAC addresses (e.g., hundreds of MAC there can be many customer MAC addresses (e.g., hundreds of MAC
addresses) associated with each CE. addresses) associated with each CE.
[P802.1ad] has devised a mechanism to alleviate MAC address learning [P802.1ad] has devised a mechanism to alleviate MAC address learning
within provider Ethernet networks that can equally be applied to within provider Ethernet networks that can equally be applied to
VPLS networks. This mechanism calls for disabling MAC address VPLS networks. This mechanism calls for disabling MAC address
learning for an S-VLAN (or a service instance) within a provider learning for an S-VLAN (or a service instance) within a provider
bridge (or PE) when there is only one ingress and one egress port bridge (or PE) when there is only one ingress and one egress port
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
associated with that service instance on that PE. In such cases, associated with that service instance on that PE. In such cases,
there is no need to learn customer MAC addresses on that PE since there is no need to learn customer MAC addresses on that PE since
the path through that PE for that service instance is fixed. For the path through that PE for that service instance is fixed. For
example, if a service instance is associated with four CEs at four example, if a service instance is associated with four CEs at four
different sites, then the maximum number of provider bridges (or different sites, then the maximum number of provider bridges (or
PEs), that need to participate in that customer MAC address PEs), that need to participate in that customer MAC address
learning, is only three regardless of how many PEs are in the path learning, is only three regardless of how many PEs are in the path
of that service instance. This mechanism can reduce the number of of that service instance. This mechanism can reduce the number of
MAC addresses learned in a H-VPLS with QinQ access configuration. MAC addresses learned in a H-VPLS with QinQ access configuration.
If the provider access network is of type Ethernet (e.g., IEEE If the provider access network is of type Ethernet (e.g., IEEE
802.1ad-based network), then the MSTP protocol can be used to 802.1ad-based network), then the MSTP protocol can be used to
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
partition the access network into several loop-free spanning tree partition the access network into several loop-free spanning tree
topologies where Ethernet service instances (S-VLANs) are topologies where Ethernet service instances (S-VLANs) are
distributed among these tree topologies. Furthermore, GVRP can be distributed among these tree topologies. Furthermore, GVRP can be
used to limit the scope of each service instance to a subset of its used to limit the scope of each service instance to a subset of its
associated tree topology (and thus limiting the scope of customer associated tree topology (and thus limiting the scope of customer
MAC address learning to that sub-tree). Finally, the MAC address MAC address learning to that sub-tree). Finally, the MAC address
disabling mechanism (described above) can be applied to that sub- disabling mechanism (described above) can be applied to that sub-
tree, to further limit the number of nodes (PEs) on that sub-tree tree, to further limit the number of nodes (PEs) on that sub-tree
that need to learn customer MAC addresses for that service instance. that need to learn customer MAC addresses for that service instance.
Furthermore, [p802.1ah] provides the capability of encapsulating Furthermore, [p802.1ah] provides the capability of encapsulating
customers' MAC addresses within the provider MAC header. A u-PE customers' MAC addresses within the provider MAC header. A u-PE
capable of this functionality can reduce the number of MAC addressed capable of this functionality can reduce the number of MAC addressed
learned significantly within the provider network for H-VPLS with learned significantly within the provider network for H-VPLS with
QinQ access as well as H-VPLS with MPLS access. QinQ access as well as H-VPLS with MPLS access.
6. Interoperability with 802.1ad Networks 6. Interoperability with 802.1ad Networks
[RFC-4762] discusses H-VPLS provider-network topologies with both [RFC-4762] discusses H-VPLS provider-network topologies with both
Ethernet [P802.1ad] as well as MPLS access networks. Therefore, it is Ethernet [P802.1ad] as well as MPLS access networks. Therefore, it is
of paramount importance to ensure seamless interoperability between important to ensure seamless interoperability between these two types
these two types of networks. of networks.
Provider bridges as specified in [P802.1ad] are intended to operate Provider bridges as specified in [P802.1ad] are intended to operate
seamlessly with customer bridges and provide the required services. seamlessly with customer bridges and provide the required services.
Therefore, if a PE is modeled based on Figures 1&2 which includes a Therefore, if a PE is modeled based on Figures 1 and 2 which includes
[802.1ad] bridge module, then it should operate seamlessly with a [802.1ad] bridge module, then it should operate seamlessly with
Provider Bridges given that the issues discussed in this draft have Provider Bridges given that the issues discussed in this draft have
been taken into account. been taken into account.
7. Acknowledgments 7. Acknowledgments
The authors would like to thank Norm Finn for his comments and The authors would like to thank Norm Finn for his comments and
feedbacks. feedbacks.
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
8. IANA Considerations 8. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
9. Security Considerations 9. Security Considerations
The security considerations in here are the same as the ones The security considerations in this document are the same as the
described in [RFC-4762], and there are no additional security ones described in [RFC-4762], and there are no additional security
aspects that need to be considered beyond the ones described in aspects that need to be considered beyond the ones described in
[RFC-4762]. [RFC-4762].
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007 10. Normative References
10. IPR Notice:
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed
to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use
of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository
at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
11. Normative References
[RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC-4762] Lasserre, M. and et al, "Virtual Private LAN Services [RFC-4762] Lasserre, M. and et al, "Virtual Private LAN Services
over MPLS", RFC 4762, January 2007 over MPLS", RFC 4762, January 2007
[P802.1ad] IEEE Draft P802.1ad/D2.4 "Virtual Bridged Local Area [P802.1ad] IEEE Draft P802.1ad/D2.4 "Virtual Bridged Local Area
Networks: Provider Bridges", Work in progress, September 2004 Networks: Provider Bridges", Work in progress, September 2004
[P802.1ag] IEEE Draft P802.1ag/D0.1 "Virtual Bridge Local Area [P802.1ag] IEEE Draft P802.1ag/D0.1 "Virtual Bridge Local Area
Networks: Connectivity Fault Management", Work in Progress, October Networks: Connectivity Fault Management", Work in Progress, October
2004 2004
12. Informative References 11. Informative References
[RFC-4665] Agustyn, W. et al, "Service Requirements for Layer-2 [RFC-4665] Agustyn, W. et al, "Service Requirements for Layer-2
Provider Provisioned Virtual Provider Networks", RFC 4665, September Provider Provisioned Virtual Provider Networks", RFC 4665, September
2006 2006
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
[RFC-4664] Andersson, L. and et al, "Framework for Layer 2 Virtual [RFC-4664] Andersson, L. and et al, "Framework for Layer 2 Virtual
Private Networks (L2VPNs)", RFC 4664, September 2006 Private Networks (L2VPNs)", RFC 4664, September 2006
[IPLS] Shah, H. and et al, "IP-Only LAN Service (IPLS)", draft-ietf- [IPLS] Shah, H. and et al, "IP-Only LAN Service (IPLS)", draft-ietf-
l2vpn-ipls-08.txt, work in progress, February 2008 l2vpn-ipls-08.txt, work in progress, February 2008
[MFA-Ether] Sajassi, A. and et al, "Ethernet Service Interworking [MFA-Ether] Sajassi, A. and et al, "Ethernet Service Interworking
Over MPLS", Work in Progress, September 2004 Over MPLS", Work in Progress, September 2004
[RFC-4448] "Encapsulation Methods for Transport of Ethernet Frames [RFC-4448] "Encapsulation Methods for Transport of Ethernet Frames
Over IP/MPLS Networks", RFC 4448, April 2006 Over IP/MPLS Networks", RFC 4448, April 2006
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
[802.1D-REV] IEEE Std. 802.1D-2003 "Media Access Control (MAC) [802.1D-REV] IEEE Std. 802.1D-2003 "Media Access Control (MAC)
Bridges". Bridges".
[802.1Q] IEEE Std. 802.1Q-2003 "Virtual Bridged Local Area [802.1Q] IEEE Std. 802.1Q-2003 "Virtual Bridged Local Area
Networks". Networks".
[RFC-4541] Christensen, M. and et al, "Considerations for IGMP and [RFC-4541] Christensen, M. and et al, "Considerations for IGMP and
MLD Snooping Switches", Work in progress, May 2004 MLD Snooping Switches", Work in progress, May 2004
skipping to change at page 19, line 4 skipping to change at page 18, line 43
Frank Brockners Frank Brockners
Cisco Systems, Inc. Cisco Systems, Inc.
Hansaallee 249 Hansaallee 249
40549 Duesseldorf 40549 Duesseldorf
Germany Germany
Email: fbrockne@cisco.com Email: fbrockne@cisco.com
Dinesh Mohan Dinesh Mohan
Nortel Networks Nortel Networks
3500 Carling Ave 3500 Carling Ave
draft-ietf-l2vpn-vpls-bridge-interop.txt November 2007
Ottawa, ON K2H8E9 Ottawa, ON K2H8E9
Email: mohand@nortel.com Email: mohand@nortel.com
Full Copyright Statement
Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on
an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE
IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL
WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY
WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE
ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS
FOR A PARTICULAR PURPOSE.
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