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Outline
> Motivation for Converging L2 Services on MPLS> Network and Service Interworking> Expectations on the New Converged Packet Network> Interworking the User Plane> Interworking the Control Plane> Interworking the Management Plane (OAM)> Conclusions> Further Reading
3
Service Convergence over MPLS
> Service providers are introducing new MPLS based packet switchedcore networks
� They are introducing Ethernet in the access> Motivations:
� Generate new revenues by broadening the range of services delivered from the IP network
� Extend the reach of existing Ethernet/FR/ATM services to new sites� Interconnect regional ATM networks over a national IP/MPLS network� Reduce CAPEX and possibly OPEX� Avoid per-service/per-technology networks
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Standard Service Convergence Solutions
> Based on Layer 2 Network and Service Interworking functions> Network Interworking:
� Allows networks to communicate transparently across different link layer technologies
� Interworking is performed at the link layer (L2) by encapsulating one link layer in the other
� Typically deployed inside the network and is not visible to end-users> Service Interworking:
� Allows CPEs to exchange service layer PDU across different link layer technologies
� Interworking is performed by terminating the link layers and translating based on knowledge of the payload service context
� Constraints visible to end-users
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Network and Service Interworking Benefits
ATM
ATMMPLS
Ethernet
Ethernet
Ethernet
ATM PW
Ethernet PW
> Network Interworking:� OPEX & CAPEX reduction across the combined service portfolio and
consolidated infrastructure� Growing existing service revenues
> Service Interworking:� Developing new revenue opportunities from a more flexible service offering
e.g. offer an Ethernet access service to customers that already have ATM or FR access to a layer 2 VPN
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Expectations of the New Converged Packet Network
> Coping with traffic growth in a cost-effective way� Enhance utilization of infrastructure
> Carrier class protection and restoration� Offer flexible levels of protection (e.g., hot-standby versus warm-standby
backup, local versus end-to-end protection)� Provide reactive and pro-active OAM capabilities
> Service level differentiation� Offer different services with different performance objectives (e.g., VoIP,
Virtual Leased Lines, Internet access)� Offer multiple grades of the same service (e.g., VoIP gold, silver)
> Intelligent edge policy decision� Ability to have visibility and to select specific network resources and apply
different policies for routing customer traffic at edge> Maintaining integrity of L2 services
� Transparent carriage of existing L2 services� Seamless interworking with new services at the user, control , and
management (OAM) planes
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Basics of Pseudo-Wires
MPLSPE /IWF PE /IWF
Pseudo Wires are the building blocks of a converged packet network
Layer 2AC
Layer 2AC
CE CE
MPLS framepayload
(L2 protocol)
Tunnel LSP
PW Label Inner Label
T-LSP Label Outer Label
MPLS Label Stack
Pseudo-wire
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Outline
> Motivation for Converging Services on a Common Packet Network
> Network and Service Interworking> Expectations of the New Converged Packet Network> Interworking the User Plane> Interworking the Control Plane> Interworking the Management Plane (OAM)> Conclusions> Further Reading
9
Some L2 VPN Terminology�
> An end-to-end virtual circuit in a L2 VPN consists of a 3 segment set: <AC, PW, AC>
� AC: attachment Circuit; PW: Pseudo-Wire> A L2 VPN circuit is homogeneous if AC and PW types are the same
� E.g., ATM circuit: <ATM AC, ATM PW, ATM AC>
> A L2 VPN circuit is heterogeneous if any two segments of the circuit are of different type
� E.g., IP interworking circuit: <ATM AC, IP PW, ATM AC>, or <ATM AC, IP PW, FR AC>
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Types of Interworking over MPLS
> Network Interworking� ATM/MPLS using <ATM AC, ATM PW, ATM AC> circuits� FR/MPLS using <FR AC, FR PW, FR AC> circuits� Ethernet/MPLS using <Eth AC, Eth PW, Eth AC> circuits� FR-ATM network interworking (FRF.5) using <FR AC, ATM/FR PW, ATM
AC> circuits> Service Interworking
� FR-ATM service interworking (FRF.8.2) using <FR AC, ATM/FR PW, ATM AC> circuits
� Ethernet interworking using <Eth/ATM/FR AC, Eth PW, Eth/ATM/FR AC> circuits
� IP interworking using <Eth/ATM/FR AC, IP PW, Eth/ATM/FR AC> circuits
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INE
ATM(PNNI)
ATM 2
ATM UNI
ATM UNI
UNI/NNI
T-LSP
PVC/SPVCATM PW
ATM 1
PE 1(ATM-MPLS
Network IWF)
PE 2
MPLS
IP/IPX/SNA
RFC2684B-PDU/R-PDU
AAL5 ATM
PE 3 (ATM-MPLS
Network IWF)
ATM UNI
ATM PW
CE 1
IP/IPX/SNA
RFC2684B-PDU/R-PDU
AAL5 ATM
IP/IPX/SNA
RFC2684B-PDU/R-PDU
ATMoMPLS
MPLS
POS/GigE
CE 2
CE 3
IP/IPX/SNA
RFC2684B-PDU/R-PDU
AAL5 ATM
ATM-MPLS Network Interworking
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FR-ATM and FR-MPLS Network Interworking over MPLS
INE
ATM(PNNI)
ATM 2
FR UNI
FR UNI
UNI/NNI
T-LSP
PVC/SPVCATM AAL5 PW
ATM 1 (FR-ATM Network
IWF � FRF.5)
PE 1(ATM-MPLS
Network IWF)
PE 2
MPLS
IP/IPX/SNA
RFC2427B-PDU/R-PDU
FR
PE 3 (FR-MPLS
Network IWF)
FR UNI
FR PW
CE 1
IP/IPX/SNA
RFC2684B-PDU/R-PDU
AAL5 ATM
IP/IPX/SNA
RFC2684B-PDU/R-PDU
ATMoMPLS
MPLS
POS/GigE
IP/IPX/SNA
RFC2427B-PDU/R-PDU
FRoMPLS
MPLS
POS/GigE
CE 2
CE 3
IP/IPX/SNA
RFC2427B-PDU/R-PDU
FR
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FR-ATM Service Interworking over MPLS
PE 2 (ATM-MPLS
Network IWF)
ATM(PNNI)
ATM 2
FR UNI
FR UNI
UNI/NNI
T-LSP
PVC/SPVCATM AAL5 PW
ATM 1 (FR-ATM Network
IWF � FRF.8.1)
PE 1(ATM-MPLS
Network IWF)
MPLS
IP/IPX/SNA
RFC2427B-PDU/R-PDU
FR
PE 3 (FRF.8.1 and
ATM-MPLS Network IWF)
FR UNI
ATM AAL5 PW
CE 1
IP/IPX/SNA
RFC2684B-PDU/R-PDU
AAL5 ATM
IP/IPX/SNA
RFC2684B-PDU/R-PDU
ATMoMPLS
MPLS
POS/GigE
IP/IPX/SNA
RFC2427B-PDU/R-PDU
FRoMPLS
MPLS
POS/GigE
CE 2
CE 3
IP/IPX/SNA
RFC2684B-PDU/R-PDU
AAL5 ATM
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FR-ATM Service Interworking over MPLS
PE 2 (Ethernet-MPLSNetwork IWF)
ATM(PNNI)
ATM 2
UNI/NNI
T-LSP
PVC/SPVCEthernet PW
PE 1
MPLS
IP/IPX/SNA
RFC2427B-PDU/R-PDU
FR
PE 3 (Ethernet-MPLSNetwork IWF)
Ethernet(VLAN) UNI
Ethernet PW
CE 1
IP/IPX
RFC2684B-PDU
AAL5 ATM
IP/IPX
Ethernet(VLAN)
EthoMPLS
MPLS
POS/GigE
CE 2
CE 3
IP/IPX
Ethernet(VLAN
Ethernet(VLAN) UNI
ATM 1 (Ethernet-ATMService IWF)
Ethernet(VLAN) UNI
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IP Interworking over MPLS
ATM(PNNI) MPLS
ATM 2
ATM 4
FR UNI
Ethernet (VLAN) UNI
UNI/NNI
UNI/NNI
T-LSP
FR UNI
T-LSPPVC/SPVC
PVC/SPVC
ATM 1
ATM 3
PE 4
PE 3
PE 1
PE 2
ATM UNI
IP PW
IP PW
IP PW
CE 1
CE 3
> Respond to InvATM ARP (Optional)
> Respond to InvATM ARP (Optional)
CE 4
CE 2
> Ethernet VLAN to IP PW mapping> ARP processing
� proxy ARP using local interface MAC
> Ethernet VLAN to IP PW mapping> ARP processing
� proxy ARP using local interface MAC
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End-to-End QoS
> Ingress Classification� MFC, DSCP, 802.1p, L2 I/F context (e.g., ATM Service category & CLP)� <CoS, DP> assigned to packet
> Ingress Policing� Per L2 CoS policing, e.g., Per VPI/VCI/CLP in a ATM AC
> Queuing and Scheduling in PE� Based on assigned <CoS, DP>
> Admission control in PE� Tunnel LSP is assigned bandwidth� PW are CACed against tunnel bandwidth
> Egress remarking in PE� Configurable mapping of <CoS, DP> to EXP
> Queuing and Scheduling in Core LSR� According to the label value and EXP value for a L-LSP� According to the EXP value for a E-LSP
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AC
Example of QoS Support
MPLSNetwork
PE1
PE2
ATM / Ethernet
ATM / Ethernet
PW on T-LSP
AC
Labels pushed with EXP based on packet�s QoSLabels pushed with EXP based on packet�s QoS
Schedule traffic based on label and/or EXP.
Labels popped
Schedule traffic based on label and/or EXP.
Labels popped
Transit LSRs schedule traffic based on label/EXP
Transit LSRs schedule traffic based on label/EXP
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Outline
> Motivation for Converging Services on a Common Packet Network
> Network and Service Interworking> Expectations of the New Converged Packet Network> Interworking the User Plane> Interworking the Control Plane> Interworking the Management Plane (OAM)> Conclusions> Further Reading
19
Connectivity Scenarios Across the MPLS Network
> Scenario 1: � Connectivity of sites attached to the MPLS network
> Scenarios 2 & 3: � Connectivity of sites attached to FR/ATM networks across the
MPLS network
> Scenario 4: � Connectivity of a site attached to a FR/ATM network to a site
attached to the MPLS network
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Scenario 1: Targeted LDP Signaling
> Targeted LDP is used for PW setup and maintenance> Provides PW setup/release and status e.g. down> draft-ietf-pwe3-control-protocol-08.txt
MPLS
Ethernet (VLAN) UNI
T-LSP
T-LSP
PW
PW
PE 4
PE 1
PE 2
ATM UNI
PW
FR UNI
FR UNI
CE 1
CE 3
PE 3
CE 2
CE 4
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Scenario 2 & 3: Integrated vs. Distributed Approaches
ATM/PNNIIP/MPLS
Integrated Model
ATM/PNNI IP/MPLS
Distributed ModelATMEdge MPLS
Edge
Interworking function supported on a single PE with both MPLS and ATM (PNNI/AINI) control planes>Direct ATM control of MPLS tunnel resources>1:1 mapping from ATM connections to PWs
ATM & MPLS control planes supported on different edge devices
>Maintains admin separation between ATM & MPLS networks
>ATM control plane tunnelled over a virtual trunk, mapped to a PW (N:1 mapping)
ATM/PNNI
ATM connections
PW
Two approaches to ATM<->MPLS network interconnection
IWF on one PE, supporting both ATM and MPLS control planes
IWF on one PE, supporting both ATM and MPLS control planes
ATM virtual trunkATM virtual trunk
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Extended PNNI
> Designed for transparently interconnecting ATM/PNNI networks using SVCs and SPVCs over MPLS core
> ATM/PNNI and MPLS both run on the PE (Integrated model)> Extension to PNNI allows it to allocate PW label on PSN tunnel
� 1:1 mapping between ATM connections and PWs, but can use any PW encapsulation (1:1, N:1, AAL5 SDU, AAL5 PDU)
� PSN tunnel looks like a virtual PNNI port
> Standardised in ATM Forum: AF-CS-0197> Interoperability demonstrated at SuperComm 2004
23
CE 1
ATM PNNI
ATMPNNI
MPLS
CE 2
RCCRCC
Sig LinkSig Link
ATM SVC/SPVCATM SVC/SPVC
Mapped to PWs
ATM/FR UNI
ATM Signaling for ATM-MPLS Network Interworking: >ATM Forum AF-CS-0197.000>draft-bocci-l2vpn-pnni-mpls-iw-00.txt
ATM/FR UNI
T-LSPT-LSP
Extended PNNI: Architecture
24
Properties of Extended PNNI
> Independence between IGP and PNNI routing domains
> Requires PNNI and MPLS on the same PE� No changes to any other switches or LSRs
> Uses any of the standard ATM PW types, but maps 1 ATM connection to 1 PW
� Simple QoS support
� Same OAM model as ATM today
> No impact on MPLS core from high ATM signalling loads
> Full transparency to all ATM switched services and future evolution of PNNI
> PNNI can be used for ATM PW protection / restoration
25
Virtual Trunking
> Range of ATM connections with the same VPI mapped to a virtual trunk at ATM edge
> Virtual trunk is mapped to a N:1 PW at the MPLS edge> Targeted at the distributed model> Virtual trunk is established by provisioning> Two QoS models under discussion:
� Implicit QoS: Each VT is a single QoS class, PW is effectively an L-LSP
� Explicit QoS: Each packet of a given VT can have a different QoStreatment, specified using MPLS EXP bits, PW is effectively an E-LSP
� Requires communication of QoS setting from ATM switch to PE.
26
ATM /PNNI
CE 1
ATM /PNNI
CE 2
ATM/FR UNI
ATMEdge
VPI N
VPI M
MPLS
ATMEdge
VT
MPLSEdge
MPLSEdge
N:1 PWN:1 PWPSN TunnelPSN TunnelVirtual trunk on ATM linkVirtual trunk on ATM link
> PNNI RCCs and Sig links tunnelled transparently over VT.> One VT for each pair of interconnected ATM switches.
ATM edge switched ATM connections into contiguous VPI ranges for
each virtual trunk, e.g. VPI = N..M
ATM edge switched ATM connections into contiguous VPI ranges for
each virtual trunk, e.g. VPI = N..M
MPLS edge maps VT to PWMPLS edge maps VT to PW
Virtual Trunking: Architecture
27
Properties of Virtual Trunking
> Independence between IGP and PNNI routing domains> Allows separation of PNNI and MPLS between ATM edge
and MPLS edge> Uses only N:1 ATM PW, maps many ATM connections
to each PW� Must be provisioned a-priori� OAM treatment of a VT needs to be defined
> No impact on MPLS core from high ATM signalling loads> Full transparency to all ATM switched services and future
evolution of PNNI> PNNI can be used for ATM PW protection / restoration> Not yet standardised: Under development in MPLS/FR Alliance
28
Scenario 4: SPVC-PW Interworking
PE 4
ATM(PNNI)
ATM 1
ATM 3
ATM 2
ATM 4
FR UNI
ATM UNI
ATM 5
PNNI RoutingIGP RoutingMP-BGP p2p Routing
Inject Learned/Configured NSAP Routes (optional)
Inject Learned/Configured NSAP Embedded IP Routes
Ethernet (VLAN) UNI
SPVC PW
ATM NNI
ATM NNI
CE 1
FR UNICE 3
CE 4
PE 1
MPLS
PE 3
LSR
CE 1
PE 2
29
Overview of SPVC-PW Interworking
> Routing� LER reachability is configured in the ATM-MPLS GW (PE1/PE3)
� LERs are assigned IP embedded NSAP addresses� PE1 advertises configured IP embedded NSAP routes into PNNI peer-group
as externally reachable prefixes� SPVC launched from PNNI endpoint
� ATM/MPLS GW (PE1/PE3) does not advertise PNNI routes to LERs� Routing interworking of PNNI and MP-BGP not required initially
> Signaling� End-to-end SPVC consists of a bi-directional PNNI source routed SPVC and a
bi-directional PW� Requires synchronization of call handling procedures between bidirectional
PNNI/AINI/UNI signaling and unidirectional LDP signaling� Limited translation of signaling messages between PNNI/AINI/UNI and LDP
Described in: draft-swallow-pwe3-spvc-iw-01.tx t
draft-watkinson-l2vpn-pnni-psn-framework-01.txt
30
Properties of SPVC-PW Interworking
> Independence between IGP and PNNI routing domains> Allows separation of PNNI and MPLS between ATM edge
and MPLS edge> Only applicable to ATM/FR S-PVCs S-PVPs> Impact on MPLS core from high ATM signalling loads
during S-PVC reroute> S-PVCs can only originate in the ATM network and cannot
extend beyond remote PE> PNNI and MPLS can be used for ATM PW and PE
protection / restoration> Under development in IETF & MPLS/FR alliance
31
Outline
> Motivation for Converging Services on a Common Packet Network
> Network and Service Interworking> Expectations of the New Converged Packet Network> Interworking the User Plane> Interworking the Control Plane> Interworking the Management Plane (OAM)> Conclusions> Further Reading
32
Convergence on IP/MPLS and Implications on OAM
> Provide and coordinate OAM at the relevant levels in the IP/MPLS network
> Proactive and reactive OAM mechanisms which are independent at all levels
Service Levele.g VRF-Ping, MAC-Ping
VC / PW Levele.g VCCV, PW status
Transport LSP Levele.g MPLS OAM
Reluctance to converge premium services over IP/MPLS without OAM as robust as today�s data networks. Critical to OPEX reduction.
33
Defect Locations
AttachmentCircuit (AC)
AttachmentCircuit (AC)
Emulated Service
Pseudo-Wire
MPLS Tunnel
CE 2CE 1 a
(L2 Network) (L2 Network)
ed
a e
b f
c
d
Defect in the L2 network
Defect on a PE AC interface
Defect on a PE MPLS interface
Defect in the MPLS network
PE 1
PW
IP L2 I/F
L2 I/F
bMPLS
c
PE 2
PW
IP L2 I/F
L2 I/F
cMPLS
f
34
OAM Interworking Models
> Homogeneous L2 VPN Circuit� AC link layer not terminated at PE� Native service OAM must run inband transparently over MPLS tunnel:
� it is used for both AC and PW defect indication� Exceptions: FR and Ethernet network interworking for a lack of
inband OAM> Heterogeneous L2 VPN Circuit
� AC link layer terminated at PE� Native service OAM always terminates at the AC endpoint in a PE
� requires PW specific defect indication� Out-of-band PW status signaling is used by default
� Exception: FR-ATM service interworking when PW uses ATM cell mode> Need to be pragmatic:
� PW status signaling is default when there is no in-band OAM on PW
35
Homogeneous Circuit OAM Model
MPLS OAM
PW OAM ≡ Segment L2 OAM
Serv
ice
Prov
ider
Dom
ain
ICMP-Ping (E2E Service OAM)
E2E L2 OAM (e.g., ATM OAM)Segment L2 OAM
AC ACPseudo-WireMPLS Tunnel
CE 2CE 1 a
(L2 Network) (L2 Network)
ed
PE 1
PW
IP L2 I/F
L2 I/F
bMPLS
c
PE 2
PW
IP L2 I/F
L2 I/F
cMPLS
f
ICMP Ping (L3 OAM)
Segment L2 OAM Segment
L2 OAM
Cus
tom
er D
omai
n
36
Homogeneous Circuit OAM Example
AIS
RDI
ATM AC ATM AC
ATM PWTunnel LSP
CE 2CE 1 a
(ATM Network) (ATM Network)
PE 1
PW
L2 I/F
PE 2
PW
L2 I/F
MPLS
MPLS
End-end ATM OAM domain
37
Heterogeneous Circuit OAM Model
MPLS OAM
PW Specific OAM
Serv
ice
Prov
ider
Dom
ain
ICMP-Ping (E2E Service OAM)
E2E L2 OAM (e.g., ATM OAM)Segment L2 OAM
AC ACPseudo-WireMPLS Tunnel
CE 2CE 1 a
(L2 Network) (L2 Network)
ed
PE 1
PW
IP L2
I/FL2 I/F
bMPLS
c
PE 2
PW
IP L2
I/FL2 I/F
cMPLS
f
ICMP Ping (L3 OAM)
Segment L2 OAM
Segment L2 OAM
Cus
tom
er D
omai
n
38
Heterogeneous Circuit OAM Example
AIS
RDI
ATM AC ATM AC
IP PWTunnel LSP
CE 2CE 1 a
(ATM Network) (ATM Network)
PE 1
PW
L2 I/F
PE 2
PW
L2 I/F
MPLS
MPLS
AIS
RDIPW Status
39
Outline
> Motivation for Converging Services on a Common Packet Network
> Expectations of the New Converged Packet Network> Network and Service Interworking> Interworking the User Plane> Interworking the Control Plane> Interworking the Management Plane (OAM)> Conclusions> Further Reading
40
> Many carriers are looking at MPLS for Service Convergence� Offering or extending the reach of revenue generating Layer 2 services
over an MPLS backbone� Converging layer 2 services to leverage the same backbone to provide
enhanced revenue generating Layer 3 services
> Two approaches to support layer 2 services over MPLS� Layer 2 Network Interworking & Service Interworking� Will require comprehensive interworking at user, control and
management planes to realise potential benefits
Conclusions
41
References*
> Network and Service User Plane Interworking� ATM PW: draft-ietf-pwe3-atm-encap-06.txt� Frame Relay PW: draft-ietf-pwe3-frame-relay-03.txt� Ethernet PW: draft-ietf-pwe3-ethernet-encap-07.txt� IP interworking PW: draft-shah-l2vpn-arp-mediation-01.txt, draft-balus-pwe3-ip-pseudowire-
01.txt� ATM-MPLS network interworking: ATM Forum af-aic-0178.001� ATM-MPLS network interworking: ITU-T Y.1411, Y.1412� FR-ATM network interworking: Frame Relay Forum FRF.5� FR-ATM service interworking: Frame Relay Forum FRF.8.2� FRF.8.2 over MPLS: MPLS FR Alliance work in progress� Ethernet interworking over MPLS: MPLS FR Alliance work in progress
> Control Plane Interworking� PW signaling: draft-ietf-pwe3-control-protocol-08.txt� ATM Signaling for ATM-MPLS Network Interworking (Extended PNNI):
� ATM Forum AF-CS-0197.000� draft-bocci-l2vpn-pnni-mpls-iw-01.txt
� ATM-PWE3 signaling interworking: � draft-swallow-pwe3-spvc-iw-01.txt� draft-watkinson-l2vpn-pnni-psn-framework-01.txt
42
References* (II)
> ATM OAM� ITU-T I.610 Recommendation
> FR OAM� PVC Management (LMI): ITU-T Q.933 Annex A� OAM: Frame Relay Forum FRF.19
> MPLS OAM� LSP-Ping and Trace-Route: draft-ietf-mpls-lsp-ping-04.txt� MPLS OAM requirements: draft-ietf-mpls-oam-requirements-02.txt� MPLS OAM framework: draft-allan-mpls-oam-frmwk-05.txt� MPLS OAM: ITU-T Y.1711
> L2 VPN and Pseudo-Wire (PW) OAM� draft-ietf-l2vpn-vpls-ldp-04.txt� draft-aissaoui-l2vpn-vpws-iw-oam-01.txt� draft-ietf-pwe3-vccv-01.txt� draft-ietf-pwe3-oam-msg-map-00.txt� draft-ietf-pwe3-atm-encap-04.txt� ITU-T Y.1413
