Internet Draft Document                      Dinesh Mohan (Editor)
Internet Draft                                              Nortel Networks
Expires: April August 2005                          Ali Sajassi (Editor)
                                                     Cisco Systems

                                                      October 2004

              VPLS

                                                     February 2005

             L2VPN OAM Requirements and Framework
             draft-ietf-l2vpn-oam-req-frmk-01.txt
             draft-ietf-l2vpn-oam-req-frmk-02.txt

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accordance with RFC 3668.

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Abstract
This draft provides framework and requirements for Virtual Private
LAN Service (VPLS) Operation, Administration and Maintenance (OAM).

Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119

RELATED DOCUMENTS

http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-l2-framework-
03.txt
05.txt
http://www.ietf.org/internet-drafts/draft-ietf-l2vpn-requirements-
03.txt

Table of Contents

Status of this Memo................................................1
Abstract...........................................................1
Conventions........................................................1
1. Introduction....................................................2 Introduction....................................................3
2. L2VPN Services & Networks.......................................4
3. L2VPN OAM Layering....................................................5 Framework.............................................5
3.1. OAM Domains...................................................6 Layering..................................................5
3.2. OAM Domains...................................................6
3.3. MEPs and MIPs.................................................6
3.4. MEP and MIP Identifiers.......................................7
3.5. OAM Framework for VPLS........................................7
3.5.1. VPLS as Bridged LAN Service.................................7
3.5.2. VPLS as a Network...........................................8
3.5.3. VPLS as LAN/VLAN Emulation..................................8
3.5.4. VPLS OAM Layering...........................................9
3.5.5. VPLS OAM Domains............................................9
3.5.6. VPLS MEPs & MIPs...................................................7
3.3. MIPs...........................................10
3.5.7. VPLS MEP and MIP Identifiers.......................................8 Identifiers...............................11
3.6. OAM Framework for VPWS.......................................11
3.7. OAM Framework for IPLS.......................................11
4. VPLS L2VPN OAM Requirements...........................................9 Requirements.........................................11
4.1. Discovery.....................................................9
4.2. VPLS OAM Requirements........................................11
4.1.1. Discovery..................................................11
4.1.2. Connectivity Fault Management.................................9
4.2.1. Management..............................11
4.1.3. Connectivity Fault Detection................................9
4.2.2. Detection...............................12
4.1.4. Connectivity Fault Verification.............................9
4.2.3. Verification............................12
4.1.5. Connectivity Fault Localization............................10
4.2.4. Localization............................12
4.1.6. Connectivity Fault Alarm...................................10
4.3. Alarm...................................12
4.1.7. Frame Loss...................................................10
4.4. Loss.................................................12
4.1.8. Frame Delay..................................................10
4.5. Delay................................................13
4.1.9. Frame Delay Variation........................................11
4.6. Variation......................................13
4.1.10. Data Path Execution..........................................11
4.7. Scalability..................................................11
4.8. Extensibility................................................12
4.9. Security.....................................................12
4.10. Execution.......................................13
4.1.11. Scalability...............................................14
4.1.12. Extensibility.............................................14
4.1.13. Security..................................................14
4.1.14. Transport Independence......................................12
4.11. Independence....................................15
4.1.15. Application Independence....................................13
4.12. Independence..................................15
4.1.16. Backward Compatibility......................................13
4.13. Availability................................................13 Compatibility....................................15

4.1.17. Availability..............................................15
4.2. VPWS OAM Requirements........................................16
4.3. IPLS OAM Requirements........................................16
5. Acknowledgments................................................13 Acknowledgments................................................16
6. Security Considerations........................................14 Considerations........................................16
7. Intellectual Property Considerations...........................14 Considerations...........................16
8. Full Copyright Statement.......................................14 Statement.......................................16
9. IPR Notice.....................................................14 Notice.....................................................17
10. Normative References..........................................15 References..........................................17
11. Informative References........................................15 References........................................17
12. Authors' Addresses............................................16 Addresses............................................18

1. Introduction

This draft provides framework and requirements for Virtual Private
LAN Service (VPLS) Operation, Administration and Maintenance (OAM).

The scope of OAM for any service and/or transport/network
infrastructure technologies can be very broad in nature. OSI has
defined the following five generic functional areas for network
management, commonly abbreviated as "FCAPS" [NM-Standards]: a) Fault
Management, b) Performance Management, c) Configuration Management,
d) Accounting Management, and e) Security Management.

This draft focuses on the Fault and Performance Management aspects.
Other functional aspects of FCAPS are for further study.

[L2VPN-FRWK] specified three different types of Layer 2 VPN (i.e.
services). These are VPWS, VPLS and IPLS. The framework and
requirements presented in this draft applies to VPLS.

Fault Management can typically be viewed in terms of the following
categories:

- Fault Detection
- Fault Verification
- Fault Isolation
- Fault Notification
- Fault Recovery

Fault Detection deals with mechanism(s) that can detect both hard
failures, such as link and device failures, and soft failures, such
as software failure, memory corruption, mis-configuration, etc.
Typically a lightweight protocol is desirable to detect the fault
and thus it would be prudent to verify the fault via Fault
Verification mechanism before taking additional steps in isolating
the fault. After verifying that a fault has occurred along the data
path, it is important to be able to isolate the fault to a given
device or link. Therefore, a Fault Isolation mechanism is needed in

Fault Management. Fault Notification mechanism can be used in
conjunction with Fault Detection mechanism to notify the upstream
and downstream devices of a fault. For example, when there is a
client/server relationship between two layered networks, networks; Fault
Detection at the server layer will require the following Fault
Notification:
- sending a forward Fault Notification into the client layer
  network(s) using the Fault Notification format appropriate to
  the client layer
- sending a backward Fault Notification, if applicable, in the
  reverse direction in the server layer network

Finally, Fault Recovery deals with recovering from the detected
failure by switching to an alternate available device or link (e.g.,
device redundancy or link redundancy).

Performance Management deals with mechanism(s) that allow
determining and measuring the performance of network/services under
consideration and notification of them. Performance Management can
be used to verify the compliance to both the service and network
level metric objectives/specifications. Performance Management
typically consists of measurement of Performance Parameters e.g.
Frame Loss, Frame Delay, Frame Delay Variation (aka Jitter) etc
across managed entities when the managed entity are in available
state. Performance Management is suspended across unavailable
managed entities. This draft introduces some of these performance
parameters.

This document provides a description and a reference model for OAM
layering and furthermore emphasizes the importance of proper
independent layering in design and development of OAM functionality.

This proposal is aligned with the current discussions in other
standard bodies and groups such as ITU-T Q.3/13, IEEE 802.1, and MEF
which are addressing Ethernet network and service OAM.

2. L2VPN Services & Networks

As described in [L2VPN-REQ], following Figure 1 shows a L2VPN
reference model. L2VPN A represents a point-to-point service while
L2VPN B represents a bridged service.

 +-----+                                   +-----+
 + CE1 +--+                             +--| CE2 |
 +-----+  |    .....................    |  +-----+
 L2VPN A  |  +----+             +----+  |  L2VPN A
          +--| PE |-- Service --| PE |--+
             +----+   Provider  +----+
            /  .      Backbone     .  \    --------_
 +-----+   /   .         |         .   \  /        \   +-----+
 + CE4 +--+    .         |         .    +-\ Access  \--| CE5 |
 +-----+       .       +----+      .      | Network |  +-----+
 L2VPN B       ........| PE |.......       \       /   L2VPN B
                       +----+   ^           -------
                         |      | logical
                         |      | switching
                      +-----+   | instance
                      | CE3 |
                      +-----+
                      L2VPN B

            Figure 1: L2VPN Reference Model

[L2VPN-FRWK] specifies VPWS, VPLS and IPLS services. VPWS is a
point-to-point service where CEs are presented with point-to-point
virtual circuits. VPLS is a bridged LAN service provided to a set of
CEs that are members of a VPN. CEs that are member of the same
service instance communicate with each other as if they are
connected via a bridged LAN. IPLS is a special VPLS which is used to
carry only IP service packets.

[L2VPN-REQ] assumes the availability of runtime monitoring protocols
while defining requirements for management interfaces. This draft
specifies the requirements and framework for operations,
administration and maintenance (OAM) protocols between network
devices.

3. L2VPN OAM Framework
3.1. OAM Layering

The point-to-point or bridged LAN functionality is emulated by a
network of PEs to which the CEs are connected. This network of PEs
can belong to a single network operator or can span across multiple
network operators. Furthermore, it can belong to a single service
provider or can span across multiple service providers. A service
provider is responsible for providing L2VPN services to its
customers; whereas, a network operator (aka facility provider)
provides the necessary facilities to the service provider(s) in
support of their services.  A network operator and a service
provider can be the same entity or they can be different
administrative organizations.

[L2VPN-REQ] assumes

Different layers involved in realizing L2VPNs include service layer
and network layers. Network layers can be iterative. In context of
L2VPNs, the availability service layers consists of runtime monitoring protocols
while defining requirements VPLS, VPWS (e.g. Ethernet,
ATM, FR, HDLC, SONET, etc. point-to-point emulation), and IPLS.
Similarly in context of L2VPNs, network layers consist of MPLS/IP
networks. The MPLS/IP networks can consist of networks links
realized by different technologies e.g. SONET, Ethernet, ATM etc.

Each layer is responsible for management interfaces. its own OAM. This draft
specifies document provides
the requirements and OAM framework and requirements for operations,
administration L2VPN services and maintenance (OAM) protocols between network
devices. networks.

3.2. OAM Domains

When discussing the OAM mechanisms tools for VPLS, L2VPNs it is important to
consider provide OAM
capabilities and functionality over each domain that the end-to-end a service can span across different types
of L2VPN networks. As an example, in case of [VPLS-LDP], the access
provider or a network on one side can be bridged network e.g. [IEEE 802.1ad], operator is responsible for. For these
reasons, it is also important that OAM frames are not allowed to
enter/exit other domains. We define an OAM domain as
described in section 11 of [VPLS-LDP]. The access a network on other
side can be MPLS based
region over which OAM frames operate unobstructed as described in section 10 explained
below.

At the edge of [VPLS-LDP]; an OAM domain, filtering constructs should prevent
OAM frames from exiting and
the core network connecting them entering that domain. OAM domains can be IP, MPLS, ATM, or SONET.
Similarly, the VPLS service instance can span across [VPLS-BGP], and
distributed VPLS as described in [ROSEN-SIG].

Therefore, it
nested but not overlapped. In other words, if there is important that a hierarchy
of the OAM mechanisms can be applied to
all these network types. Each such network may be associated with domains, the OAM messages of a
separate administrative higher-level domain and also multiple such networks may
be associated with a single administrative domain. Different types
of pseudo wires may be in use to support end-to-end L2VPNs.
Therefore, for L2VPN OAM, it is important to ensure that pass
transparently through the lower-level domains but the OAM
mechanisms are independent messages
of a lower-level domain get blocked/filtered at the underlying transport mechanisms
and solely rely on layer 2 services, e.g. for VPLS service, edge of that
domain.

In order to facilitate the
transparency processing of OAM mechanisms must be ensured over underlying
transport technologies such as MPLS, IP, etc.

3. messages, each OAM Layering

Figure 2 shows an example of
domain can be associated with a VPLS service (with two CE belonging level at which it operates. Higher
level OAM domains can contain lower level OAM domains but the
converse is not true.

A PE can be part of several OAM domains with each interface
belonging to the same or a different OAM domain. A PE shall block
outgoing OAM messages and filter out incoming OAM messages whose
domain level is lower or same to the one configured on that
interface and pass through the OAM messages whose domain level is
higher than the one configured on that interface.

Generically, L2VPNs can be viewed as consisting of customer A) across OAM
domain, service provider OAM domain, and network operator OAM domain
as depicted later in Figure 3.

3.3. MEPs and MIPs

Maintenance End Points (MEPs) are responsible for origination and
termination of OAM messages. MEPs are located at the edge of their
corresponding OAM domains. Maintenance Intermediate Points (MIPs)
are located within their corresponding OAM domains and they normally

pass OAM messages but never initiate them. Since MEPs are located at
the edge of their OAM domains, they are responsible for filtering
outbound OAM frames from leaving the OAM domain or inbound OAM
frames from entering the OAM domain. MEPs and MIPs correspond to a
PE or more specifically to an interface of a PE. For example, an OAM
message can be said to originate from an ingress PE or more
specifically an ingress interface of that PE.

Since OAM domains are hierarchical as described above, the MEPs and
MIPs associated with the OAM domains become hierarchical as well. A
MEP of a higher-level OAM domain is always a MEP of a lower-level
OAM domain but the converse is not always true since the MEP of
lower-level OAM domain can either be MIP or a MEP of a higher-level
OAM domain. Furthermore, the MIPs of a lower-level OAM domain are
always transparent to the higher-level OAM domain (e.g., OAM
messages of a higher-level OAM domain are not seen by MIPs of a
lower-level OAM domain and get passed through them transparently).

3.4. MEP and MIP Identifiers

As mentioned previously, OAM at each layer should be independent of
other layers e.g. service layer OAM should be independent of
underlying transport layer. MEPs and MIPs at each layer should be
identified with layer specific identifiers.

3.5. OAM Framework for VPLS

Virtual Private LAN Service (VPLS) is used in different contexts. In
general, VPLS is used in the following contexts: a) as a bridged LAN
service provider over networks, some of which are MPLS/IP, b) as an MPLS/IP
network marked by UPE supporting these bridged LAN services, and
NPE devices. More c) as LAN/VLAN
emulation.

3.5.1. VPLS as Bridged LAN Service

The most common definition for VPLS is for bridged LAN service over
an MPLS/IP network. The service coverage is considered end-to-end
from UNI to UNI (or AC to AC) among the CE devices and it provides a
virtual LAN service to the attach CEs belonging to that service
instance. The reason it is called bridged LAN service is because the same Customer
VPLS-capable PE provide this end-to-end virtual LAN service
performing bridging functions (either full or a subset) as described
in the [L2VPN-FRWK]. A VPLS service instance is also analogous to a
VLAN provided by IEEE 802.1Q networks since each VLAN provides a
Virtual LAN service to its MAC users. Therefore, when a part of the
service provider network is Ethernet based (such as H-VPLS with QinQ
access network), there is a one-to-one correspondence between a VPLS
service instance and its corresponding provider VLAN in the service
provider Ethernet network. To check the end-to-end service
integrity, service level OAM mechanisms are needed.

3.5.2. VPLS as a Network

Sometimes VPLS is also used to refer to the underlying network that
supports bridged LAN services. This network can be
connected across customer's different sites. Service provider an end-to-end
MPLS/IP network as H-VPLS with MPLS/IP access or can be a hybrid
network is segmented into consisting of MPLS/IP core network and two types of Ethernet access

network. Figure 2(A) shows network as in
H-VPLS with QinQ access. In either case, the bridged access network represented by
its bridge components marked "B", and consists of a
set of VPLS-capable PE devices capable of performing bridging
functions (either full or a subset). These VPLS-capable PE devices
can be arranged in a certain topology such as hierarchical topology
(H-VPLS) or distributed topology (D-VPLS) or some other topologies
such as multi-tier or star topologies. To check the MPLS access and core network represented by MPLS components marked "P". Figure 2(B) shows
integrity regardless of the service/network view at network topology, network level OAM
mechanisms are needed for the Ethernet MAC layer marked by "E".

     ---                                                   ---
    /   \         ------      -------      ----           /   \
    | A CE--     /      \    /       \    /    \       --CE A |
    \   /   \   /        \  /         \  /      \     /   \   /
     ---     --UPE       NPE          NPE        UPE--     ---
                \        /  \         /  \      /
                 \      /    \       /    \    /
                  ------      -------      ----

 (A)    CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE

 (B)    E------E---E--E---E------------E----------E-----E

            Figure 2: Service specific device view

As shown in Figure 2(B), VPLS networks.

3.5.3. VPLS as LAN/VLAN Emulation

Sometimes VPLS also refers to LAN/VLAN emulation. In such context,
VPLS only refers to the devices full mesh of PWs with Ethernet
functionality are visible split horizon that
emulates a LAN segment over MPLS/IP network for a given service
instance. Since the emulated LAN segment is presented as a Virtual
LAN (VLAN) to the bridge module of a VPLS-capable PE, emulated
segment is also referred to as an emulated VLAN. The OAM mechanisms operating at Ethernet
MAC layer
in this context refer primarily to integrity check of the full mesh
of PWs and the P devices are invisible. Therefore, ability to detect and recover from partial mesh
failure.

When discussing the OAM along
the path of P devices (e.g., between two PEs) is covered by
transport layer and mechanisms for VPLS, it is outside important to
consider that the scope end-to-end service can span across different types
of this document.

3.1.          OAM Domains L2VPN networks. As an example, in case of [VPLS-LDP], the access
network on one side can be bridged network e.g. [IEEE 802.1ad], as
described in section 11 of [VPLS-LDP]. The access network on other
side can be MPLS based as described in section 10 of [VPLS-LDP]; and
the core network connecting them can be IP, MPLS, ATM, or SONET.
Similarly, the previous section, a VPLS service for a given
customer instance can span across one or more service providers [VPLS-BGP], and network
operators. Therefore, when discussing OAM tools for
distributed VPLS as described in [ROSEN-SIG].

Therefore, it is important to provide OAM capabilities and functionality over each
domain that a service provider or a network operator is responsible
for. For these reasons, it is also important that the OAM frames are not
allowed mechanisms can be applied to enter/exit other domains. We define an OAM domain as a
all these network region over which OAM frames operate unobstructed as
explained below.

At the edge of an OAM domain, filtering constructs should prevent
OAM frames from exiting types. Each such network may be associated with a
separate administrative domain and entering that domain. OAM domains can also multiple such networks may
be
nested but not overlapped. In other words, if there is associated with a hierarchy
of the OAM domains, the OAM messages single administrative domain. Different types
of a higher-level domain pass
transparently through the lower-level domains but pseudo wires may be in use to support end-to-end L2VPNs.
Therefore, for L2VPN OAM, it is important to ensure that the OAM messages
mechanisms are independent of a lower-level domain get blocked/filtered at the edge of that
domain.

In order to facilitate underlying transport mechanisms
and solely rely on layer 2 services, e.g. for VPLS service, the processing
transparency of OAM messages, each domain
can mechanisms must be associated with a level at which it operates. Domains with
larger level numbers can contain domain ensured over underlying
transport technologies such as MPLS, IP, etc.

This proposal is aligned with smaller level numbers
but the converse is not true.

A PE can be part current discussions in other
standard bodies and groups such as ITU-T Q.3/13, IEEE 802.1, and MEF
which are addressing Ethernet network and service OAM.

3.5.4. VPLS OAM Layering

Figure 2 shows an example of several domains with each interface a VPLS service (with two CE belonging
to
same or different domains. A PE shall block outgoing OAM messages customer A) across a service provider network marked by UPE and filter out incoming messages whose domain level is lower or
equal
NPE devices. More CE devices belonging to the one configured on that interface and pass through the
messages whose domain level is greater than the one configured on
that interface.

Figure 3 depicts three domains: (A) customer domain which is among
the CEs same Customer A can be
connected across different sites of a given customer, (B) service customer. Service provider domain which
network is
among the edge PEs segmented into core network and two types of access
network. Figure 2(A) shows the given service provider, bridged access network represented by
its bridge components marked "B", and (C) the MPLS access and core
network
operator domain which is among represented by MPLS components marked "P". Figure 2(B) shows
the PEs of a given operator. service/network view at the Ethernet MAC layer marked by "E".

     ---                                                   ---
    /   \         ------      -------      ----           /   \
    | A CE--     /      \    /       \    /    \       --CE A |
    \   /   \   /        \  /         \  /      \     /   \   /
     ---     --UPE       NPE          NPE        UPE--     ---
                \        /  \         /  \      /
                 \      /    \       /    \    /
                  ------      -------      ----

 (A)     |<----------------------------------------------->|
                              customer    CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE

 (B)            |<---------------------------------->|
                              provider

(C)            |<--------->|<----------->|<-------->|
                 operator     operator     operator    E------E---E--E---E------------E----------E-----E

            Figure 3: OAM Domains

3.2.          MEPs & MIPs

Maintenance End Points (MEPs) 2: Service specific device view

As shown in Figure 2(B), only the devices with Ethernet
functionality are responsible for origination and
termination of visible to OAM messages. MEPs are located mechanisms operating at Ethernet
MAC layer and the edge of their
corresponding OAM domains. Maintenance Intermediate Points (MIPs) P devices are located within their corresponding domains and they normally
pass invisible. Therefore, the OAM messages but never initiate them. Since MEPs are located at along
the edge path of their domains, they are responsible for filtering
outbound OAM frames from leaving P devices (e.g., between two PEs) is covered by
transport layer and it is outside the domain or inbound scope of this document.

3.5.5. VPLS OAM frames
from entering Domains

As described in the domain. MEPs and MIPs correspond to previous section, a PE or more
specifically to an interface of VPLS service for a PE. For example, an OAM message given
customer can be said to originate from an ingress PE span across one or more specifically an
ingress interface of that PE.

Since OAM domains are hierarchical as described above, the MEPs service providers and
MIPs associated with the OAM domains become hierarchical as well. A
MEP of a higher-level domain is always a MEP of a lower-level domain
but the converse is not always true since the MEP of lower-level network
operators.

Figure 3 depicts three domains: (A) customer domain can either be MIP or a MEP of a higher-level domain.
Furthermore, which is among
the MIPs CEs of a lower-level given customer, (B) service provider domain are always transparent

to which is
among the higher-level domain (e.g., OAM messages edge PEs of a higher-level the given service provider, and (C) network
operator domain are not seen by MIPs which is among the PEs of a lower-level domain and get passed
through them transparently). given operator.

     ---                                                   ---
    /   \         ------      -------      ----           /   \
    | A   CE--     /      \    /       \    /    \       --CE A   |
    \   /   \   /        \  /         \  /      \     /   \   /
     ---     --UPE       NPE          NPE        UPE--     ---
                \        /  \         /  \      /
                 \      /    \       /    \    /
                  ------      -------      ----
(A)    CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE     |<----------------------------------------------->|
                              customer
(B)    E------E---E--E---E------------E----------E-----E            |<---------------------------------->|
                              provider
(C)    MEP---MIP--------------------------------MIP---MEP
                           Customer Domain

 (D)          MEP--------MIP-----------MIP-------MEP
                           Provider domain

 (E)          MEP-MIP-MIP-MEP----------MEP-------MEP
                 Operator     Operator    Operator
                  domain       domain      domain

 (F)                      MEP--MIP-MIP-MEP--MIP--MEP
                                MPLS        MPLS
                               domain      domain            |<--------->|<----------->|<-------->|
                 operator     operator     operator

                      Figure 4: 3: OAM Domains, Domains

3.5.6. VPLS MEPs & MIPs

As shown in Figure 4, (C) represents those MEPs and MIPs that are
visible within the customer domain. (D) represents the MEPs and MIPs
visible within the service provider domain, while (E) represents the
MEPs and MIPs visible within each operator domain. Further, (F)
represents the MEPs and MIPs corresponding to the MPLS layer and may
apply MPLS based mechanisms. The MPLS layer shown in Figure 4 is
just an example and specific OAM mechanisms are outside the scope of
this document.

3.3.

     ---                                                   ---
    /   \         ------      -------      ----           /   \
    | A CE--     /      \    /       \    /    \       --CE A |
    \   /   \   /        \  /         \  /      \     /   \   /
     ---     --UPE       NPE          NPE        UPE--     ---
                \        /  \         /  \      /
                 \      /    \       /    \    /
                  ------      -------      ----

 (A)    CE----UPE--B--B--NPE---P--P---NPE---P----UPE----CE
 (B)    E------E---E--E---E------------E----------E-----E
 (C)    MEP---MIP--------------------------------MIP---MEP
                           Customer Domain
 (D)          MEP--------MIP-----------MIP-------MEP
                           Provider domain
 (E)          MEP-MIP-MIP-MEP----------MEP-------MEP
                 Operator     Operator    Operator
                  domain       domain      domain

 (F)                      MEP--MIP-MIP-MEP--MIP--MEP
                            MPLS domain  MPLS domain

                  Figure 4: OAM Domains, MEPs & MIPs

3.5.7. VPLS MEP and MIP Identifiers

As mentioned previously, L2VPN OAM should be independent of
underlying transport layer and only be dependent on service layer,
e.g. Ethernet MAC layer in case of VPLS service. As an example,

In VPLS, for Ethernet MAC layer, the MEPs and MIPs should be
identified with their Ethernet MAC addresses. As described in [VPLS-LDP], [VPLS-
LDP], VPLS instance can be identified in an Ethernet domain (e.g.,
8021.d domain) using VLAN tag (service tag) while in an MPLS/IP
network, PW-ids are used. Both PW-ids and VLAN tags for a given VPLS
instance are associated with a Service Identifier (e.g., VPN
identifier). MEPs and MIPs Identifiers, i.e. MEP Ids and MIP Ids
must be unique within their corresponding Service Identifiers within
the OAM domains.

For Ethernet services e.g. VPLS, Ethernet frames are used for OAM
messages and the source MAC address of the OAM frames represent the
source MEP in that domain. For unicast Ethernet OAM frames, the
destination MAC address represents the destination MEP in that
domain. For multicast Ethernet OAM frames, the destination MAC
addresses corresponds to all MEPs in that domain.

3.6. OAM Framework for VPWS
TBD

3.7. OAM Framework for IPLS
FFS

4.        VPLS L2VPN OAM Requirements

4.1. VPLS OAM Requirements

4.1.1. Discovery

Discovery allows a service aware device to learn about other devices
that support the same service instance within a given domain.

Discovery also allows a service aware device to learn sufficient
information (e.g. IP addresses, MAC addressed etc.) from other
service aware devices such that OAM messages can be exchanged among
the service aware devices.

(R1) OAM MUST allow a service aware device to discover other devices
that share the same service instance(s) within a given OAM domain.

4.2.

4.1.2. Connectivity Fault Management

Service is realized by exchanging service frames/packets between
devices that support the service instance. To allow the exchange of

service frames, connectivity between these service aware devices is
required.

4.2.1.

4.1.3. Connectivity Fault Detection

To ensure service, pro-active connectivity monitoring is required.
Connectivity monitoring facilitates connectivity fault detection.

(R2a) OAM MUST allow pro-active connectivity monitoring between two
service aware devices that support the same service instance within
a given OAM domain.

4.2.2.

4.1.4. Connectivity Fault Verification

Once a connectivity fault is detected, connectivity fault
verification may be performed.

(R2b) OAM MUST allow connectivity fault verification between two
service aware devices that support the same service instance within
a given OAM domain.

4.2.3.

4.1.5. Connectivity Fault Localization

Further, localization of connectivity fault may be carried out.

(R2c) OAM MUST allow connectivity fault localization between two
service aware devices that support the same service instance within
a given OAM domain.

4.2.4.

4.1.6. Connectivity Fault Alarm

Typically, when connectivity fault is detected and optionally
verified, service device may notify the EMS/NMS (Element Management
System/Network Management System).

However, a single transport/network fault may cause multiple
services to fail causing multiple connectivity faults. Therefore,
OAM must allow alarm notification to allow suppression of service
connectivity fault notifications.

(R2d) OAM MUST allow forwarding of transport/network fault
indications to those service aware devices that support service
instance affected by the fault.

4.3.

4.1.7. Frame Loss

A service may be considered degraded if it is sensitive to service
frames/packets loss during transit between the service aware
devices. To determine if a service is degraded due to frame/packet
loss, measurement of frame/packet loss is required.

(R3) OAM MUST support measurement of per-service frame/packet loss
between two service aware devices that support the same service
instance within a given OAM domain.

4.4.

4.1.8. Frame Delay

A service may be sensitive to delay experienced by the service
frames/packets during transit between the service aware devices. To
determine if a service is degraded due to frame/packet delay,
measurement of frame/packet delay is required.

Frame/packet delay measurement can be of two types:

One-way delay
One-way delay is used to characterize certain applications like
multicast and broadcast applications. The measurement for one-way
delay usually requires clock synchronization between two devices in
question.

Two-way delay
Two-way delay or round-trip delay does not require clock
synchronization between two devices involved in measurement and is
usually sufficient to determine the frame/packet delay being
experienced.

(R4a) OAM MUST support measurement of per-service two-way
frame/packet delay between two service aware devices that support
the same service instance within a given OAM domain.

(R4b) OAM SHOULD support measurement of per-service one-way
frame/packet delay between two service aware devices that support
the same service instance within a given OAM domain.

4.5.

4.1.9. Frame Delay Variation

A service may be sensitive to delay variation experienced by the
service frames/packets during transit between the service aware
devices. To determine if a service is degraded due to frame/packet
delay variation, measurement of frame/packet delay variation is
required. For frame/packet delay variation measurements, one-way
mechanisms are considered to be sufficient.

(R5) OAM MUST support measurement of per-service frame/packet delay
variation between two service aware devices that support the same
service instance within a given OAM domain.

4.6.

4.1.10. Data Path Execution

If the OAM frames flow across a different path than the one used by
service frames/packets, accurate measurement and/or determination of

service state may not be made. Therefore data path, i.e. the one
being taken by service frames/packets, must be used for the service
OAM.

(R6) OAM frames MUST be forwarded along the same path as the
service/data frames.

4.7.

4.1.11. Scalability

Mechanisms developed for OAM need to be such that per-service OAM
can be supported even though the OAM may only be used for limited
services e.g. premium services and may not be used for best effort
services.

Note: The specific numbers or range of services should align with
the [L2VPN-FRWK]

(R7) OAM MUST be scalable such that a service device can support OAM
for each service that is supported by the device.

4.8.

4.1.12. Extensibility

Extensibility is intended to allow introduction of additional
functionality in future such that backward compatibility can be
maintained i.e. when working with older version devices, service OAM
with reduced functionality is still possible.

(R8) OAM MUST be extensible such that new functionality and
information elements related to this functionality can be introduced
in future.

4.9.

4.1.13. Security

OAM frames belonging to an OAM domain originate and terminate within
that OAM domain. Security implies that an OAM domain must be capable
of filtering OAM frames. The filtering is such that the OAM frames
are prevented from leaking outside their domain. Also, OAM frames
from outside the OAM domains should be either discarded (when such
OAM frames belong to same or lower-level OAM domain) or
transparently passed (when such OAM frames belong to a higher-level
OAM domain).

(R9a) OAM frames MUST be prevented from leaking outside their OAM
domain.

(R9b) OAM frames from outside an OAM domain MUST be prevented from
entering the OAM domain when such OAM frames belong to the same
level or lower-level OAM domain.

(R9c) OAM frames from outside an OAM domain MUST be transported
transparently inside the OAM domain when such OAM frames belong to
the higher-level OAM domain.

4.10.

4.1.14. Transport Independence

Service frame/packets delivery is carried out across transport
infrastructure, also called network infrastructure. Though specific
transport/network technologies may provide their own OAM
capabilities, Service OAM must be independently supported as many
different transport/network technologies can be used to carry
service frame/packets.

(R10a) OAM MUST be independent of the underlying transport/network
technologies and specific transport/network OAM capabilities.

(R10b) OAM MAY allow adaptation/interworking with specific
transport/network OAM functions. For example, this would be useful
to allow Fault Notifications from transport/network layer(s) to be
sent to service layer.

4.11.

4.1.15. Application Independence

Service itself may be used to carry application frame/packets. The
application may use its own OAM; service OAM must not be dependent
on application OAM. As an example, a VPLS service may be used to
carry IP traffic; however, VPLS OAM should not assume IP or rely on
the use of IP level OAM functions.

(R11a) OAM MUST be independent of the application technologies and
specific application OAM capabilities.

4.12.

4.1.16. Backward Compatibility

Service OAM should be such that non-service aware and/or OAM
incapable devices in the middle of the OAM domain should be able to
forward the OAM frames similar to the regular service/data
frames/packets.

(R12) OAM MUST be defined such that devices not supporting the OAM
are able to forward the OAM frames in a similar fashion as the
regular service/data frames/packets.

4.13.

4.1.17. Availability

A service may be considered unavailable if the service
frames/packets do not reach their intended destination (e.g.
connectivity is down or frame/packet loss is occurring) or the

service is degraded (e.g. frame/packet delay and/or delay variation
threshold is exceeded).

Entry and exit conditions may be defined for unavailable state.
Availability itself may be defined in context of service type.

Since availability measurement may be associated with connectivity,
frame/packet loss, frame/packet delay and frame/packet delay
variation measurements, no additional requirements are specified
currently.

4.2. VPWS OAM Requirements
TBD

4.3. IPLS OAM Requirements
FFS

5. Acknowledgments

The authors would like to thank Shahram Davari, Norm Finn, Vasile
Radoaca, Thomas Nadeau, and Monique Morrow for their contributions
and review.

The authors would also like to thank Yoav Cohen, Marc Holness,
Malcolm Betts, Paul Bottorff, Dave Allan, and Hamid-ould Brahim for
their valuable feedback.

6. Security Considerations

Security issues resulting from this draft will be discussed in
greater depth at a later point.  It is recommended in [RFC3036] that
LDP security (authentication) methods be applied.  This would
prevent unauthorized participation by a PE in a VPLS.  Traffic
separation for a VPLS is effected by using VC labels.  However, for
additional levels of security, the customer MAY deploy end-to-end
security, which is out of the scope of this draft.  In addition, the
L2FRAME] document describes security issues in greater depth.

7. Intellectual Property Considerations

This document is being submitted for use in IETF standards
discussions.

8. Full Copyright Statement

Copyright (C) The Internet Society (2004). 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 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.

9. 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
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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.

10. Normative References

[NM-Standards] "TMN Management Functions", M.3400, February 2000.

[RFC3036] "LDP Specification", RFC 3036, January 2001.

11. Informative References

[PWE3-ETHERNET] "Encapsulation Methods for Transport of Ethernet
Frames Over IP/MPLS Networks", draft-ietf-pwe3-ethernet-encap-
08.txt, Work in progress, September 2004.

[L2VPN-REQ] "Service Requirements for Layer-2 Provider Provisioned
Virtual Private Networks", draft-ietf-l2vpn-requirements-02.txt,
Work in progress, September 2004.

[L2VPN-FRWK] "Framework for Layer 2 Virtual Private Networks
(L2VPNs)", draft-ietf-l2vpn-l2-framework-05.txt, Work in Progress,
June 2004.

[IEEE 802.1ad] "IEEE standard for Provider Bridges", Work in
Progress, September 2004.

[ROSEN-SIG] "Provisioning Models and Endpoint Identifiers in L2VPN
Signaling", draft-ietf-l2vpn-signaling-02.txt, Work in progress,
September 2004.

[VPLS-LDP] "Virtual Private LAN Services over MPLS",
draft-ietf-l2vpn-vpls-ldp-05.txt, Work in progress, September 2004.

[VPLS-BGP] "Virtual Private LAN Service",
draft-ietf-l2vpn-vpls-bgp-02.txt, Work in progress, May 2004.

12. Authors' Addresses

Dinesh Mohan
Nortel Networks
3500 Carling Ave
Ottawa, ON K2H8E9
Email: mohand@nortelnetworks.com mohand@nortel.com

Ali Sajassi
Cisco Systems, Inc.
170 West Tasman Drive
San Jose, CA 95134
Email: sajassi@cisco.com