RFC 4110
A Framework for Layer 3 Provider-Provisioned Virtual Private Networks (PPVPNs)
5. Interworking Interface
This section describes interworking between different layer 3 VPN approaches. This may occur either within a single SP network, or at an interface between SP networks.5.1. Interworking Function
Figure 2.5 (see section 2.1.3) illustrates a case where one or more PE devices sits at the logical interface between two different layer 3 VPN approaches. With this approach the interworking function occurs at a PE device which participates in two or more layer 3 VPN approaches. This might be physically located at the boundary between service providers, or might occur at the logical interface between different approaches within a service provider. With layer 3 VPNs, the PE devices are in general layer 3 routers, and are able to forward layer 3 packets on behalf of one or more private networks. For example, it may be common for a PE device supporting layer 3 VPNs to contain multiple logical VFIs (sections 1, 2, 3.3.1, 4.4.2) each of which supports forwarding and routing for a private network. The PE which implements an interworking function needs to participate in the normal manner in the operation of multiple approaches for supporting layer 3 VPNs. This involves the functions discussed elsewhere in this document, such as VPN establishment and maintenance, VPN tunneling, routing for the VPNs, and QoS maintenance. VPN establishment and maintenance information, as well as VPN routing information will need to be passed between VPN approaches. This might involve passing of information between approaches as part of the interworking function. Optionally this might involve manual configuration so that, for example, all of the participants in the VPN on one side of the interworking function considers the PE performing the interworking function to be the point to use to contact a large number of systems (comprising all systems supported by the VPN located on the other side of the interworking function).5.2. Interworking Interface
Figure 2.6 (see section 2.1.3) illustrates a case where interworking is performed by use of tunnels between PE devices. In this case each PE device participates in the operation of one layer 3 VPN approach. Interworking between approaches makes use of per-VPN tunnels set up between PE. Each PEs operates as if it is a normal PEs, and considers each tunnel to be associated with a particular VPN.
Information can then be transmitted over the interworking interface in the same manner that it is transmitted over a CE to PE interface. In some cases establishment of the interworking interfaces may require manual configuration, for example to allow each PE to determine which tunnels should be set up, and which private network is associated with each tunnel.5.2.1. Tunnels at the Interworking Interface
In order to implement an interworking interface between two SP networks for supporting one or more PPVPN spanning both SP networks, a mechanism for exchanging customer data as well as associated control data (e.g., routing data) should be provided. Since PEs of SP networks to be interworked may only communicate over a network cloud, an appropriate tunnel established through the network cloud will be used for exchanging data associated with the PPVPN realized by interworked SP networks. In this way, each interworking tunnel is assigned to an associated layer 3 PE-based VPN; in other words, a tunnel is terminated by a VFI (associated with the PPVPN) in a PE device. This scenario results in implementation of traffic isolation for PPVPNs supported by an Interworking Interface and spanning multiple SP networks (in each SP network, there is no restriction in applied technology for providing PPVPN so that both sides may adopt different technologies). The way of the assignment of each tunnel for a PE-based VPN is specific to implementation technology used by the SP network that is inter-connected to the tunnel at the PE device. The identifier of layer 3 PE-based VPN at each end is meaningful only in the context of the specific technology of an SP network and need not be understood by another SP network interworking through the tunnel. The following tunneling mechanisms may be used at the interworking interface. Available tunneling mechanisms include (but are not limited to): GRE, IP-in-IP, IP over ATM, IP over FR, IPsec, and MPLS. o GRE The tunnels at interworking interface may be provided by GRE [RFC2784] with key and sequence number extensions [RFC2890].
o IP-in-IP
The tunnels at interworking interface may be provided by IP-in-IP
[RFC2003] [RFC2473].
o IP over ATM AAL5
The tunnels at interworking interface may be provided by IP over
ATM AAL5 [RFC2684] [RFC2685].
o IP over FR
The tunnels at interworking interface may be provided by IP over
FR.
o IPsec
The tunnels at interworking interface may be provided by IPsec
[RFC2401] [RFC2402].
o MPLS
The tunnels at interworking interface may be provided by MPLS
[RFC3031] [RFC3035].
5.3. Support of Additional Services
This subsection describes additional usages for supporting QoS/SLA,
customer visible routing, and customer visible multicast routing, as
services of layer 3 PE-based VPNs spanning multiple SP networks.
o QoS/SLA
QoS/SLA management mechanisms for GRE, IP-in-IP, IPsec, and MPLS
tunnels were discussed in sections 4.3.6 and 4.5. See these
sections for details. FR and ATM are capable of QoS guarantee.
Thus, QoS/SLA may also be supported at the interworking interface.
o Customer visible routing
As described in section 3.3, customer visible routing enables the
exchange of unicast routing information between customer sites
using a routing protocol such as OSPF, IS-IS, RIP, and BGP-4. On
the interworking interface, routing packets, such as OSPF packets,
are transmitted through a tunnel associated with a layer 3 PE-based
VPN in the same manner as that for user data packets within the
VPN.
o Customer visible multicast routing
Customer visible multicast routing enables the exchange of
multicast routing information between customer sites using a
routing protocol such as DVMRP and PIM. On the interworking
interface, multicast routing packets are transmitted through a
tunnel associated with a layer 3 PE-based VPN in the same manner as
that for user data packets within the VPN. This enables a
multicast tree construction within the layer 3 PE-based VPN.
5.4. Scalability Discussion
This subsection discusses scalability aspect of the interworking
scenario.
o Number of routing protocol instances
In the interworking scenario discussed in this section, the number
of routing protocol instances and that of layer 3 PE-based VPNs are
the same. However, the number of layer 3 PE-based VPNs in a PE
device is limited due to resource amount and performance of the PE
device. Furthermore, each tunnel is expected to require some
bandwidth, but total of the bandwidth is limited by the capacity of
a PE device; thus, the number of the tunnels is limited by the
capabilities of the PE. This limit is not a critical drawback.
o Performance of packet transmission
The interworking scenario discussed in this section does not place
any additional burden on tunneling technologies used at
interworking interface. Since performance of packet transmission
depends on a tunneling technology applied, it should be carefully
selected when provisioning interworking. For example, IPsec places
computational requirements for encryption/decryption.
6. Security Considerations
Security is one of the key requirements concerning VPNs. In network
environments, the term security currently covers many different
aspects of which the most important from a networking perspective are
shortly discussed hereafter.
Note that the Provider-Provisioned VPN requirements document explains
the different security requirements for Provider-Provisioned VPNs in
more detail.
6.1. System Security
Like in every network environment, system security is the most important security aspect that must be enforced. Care must be taken that no unauthorized party can gain access to the network elements that control the VPN functionality (e.g., PE and CE devices). As the VPN customers are making use of the shared SP's backbone, the SP must ensure the system security of its network elements and management systems.6.2. Access Control
When a network or parts of a network are private, one of the requirements is that access to that network (part) must be restricted to a limited number of well-defined customers. To accomplish this requirement, the responsible authority must control every possible access to the network. In the context of PE-based VPNs, the access points to a VPN must be limited to the interfaces that are known by the SP.6.3. Endpoint Authentication
When one receives data from a certain entity, one would like to be sure of the identity of the sending party. One would like to be sure that the sending entity is indeed whom he or she claims to be, and that the sending entity is authorized to reach a particular destination. In the context of layer 3 PE-based VPNs, both the data received by the PEs from the customer sites via the SP network and destined for a customer site should be authenticated. Note that different methods for authentication exist. In certain circumstances, identifying incoming packets with specific customer interfaces might be sufficient. In other circumstances, (e.g., in temporary access (dial-in) scenarios), a preliminary authentication phase might be requested. For example, when PPP is used. Or alternatively, an authentication process might need to be present in every data packet transmitted (e.g., in remote access via IPsec). For layer 3 PE-based VPNs, VPN traffic is tunneled from PE to PE and the VPN tunnel endpoint will check the origin of the transmitted packet. When MPLS is used for VPN tunneling, the tunnel endpoint
checks whether the correct labels are used. When IPsec is used for VPN tunneling, the tunnel endpoint can make use of the IPsec authentication mechanisms. In the context of layer 3 provider-provisioned CE-based VPNs, the endpoint authentication is enforced by the CE devices.6.4. Data Integrity
When information is exchanged over a certain part of a network, one would like to be sure that the information that is received by the receiving party of the exchange is identical to the information that was sent by the sending party of the exchange. In the context of layer 3 PE-based VPNs, the SP assures the data integrity by ensuring the system security of every network element. Alternatively, explicit mechanisms may be implemented in the used tunneling technique (e.g., IPsec). In the context of layer 3 provider-provisioned CE-based VPNs, the underlying network that will tunnel the encapsulated packets will not always be of a trusted nature, and the CE devices that are responsible for the tunneling will also ensure the data integrity, e.g., by making use of the IPsec architecture.6.5. Confidentiality
One would like that the information that is being sent from one party to another is not received and not readable by other parties. With traffic flow confidentiality one would like that even the characteristics of the information sent is hidden from third parties. Data privacy is the confidentiality of the user data. In the context of PPVPNs, confidentiality is often seen as the basic service offered, as the functionalities of a private network are offered over a shared infrastructure. In the context of layer 3 PE-based VPNs, as the SP network (and more precisely the PE devices) participates in the routing and forwarding of the customer VPN data, it is the SP's responsibility to ensure confidentiality. The technique used in PE-based VPN solutions is the ensuring of PE to PE data separation. By implementing VFI's in the PE devices and by tunneling VPN packets through the shared network infrastructure between PE devices, the VPN data is always kept in a separate context and thus separated from the other data.
In some situations, this data separation might not be sufficient. Circumstances where the VPN tunnel traverses other than only trusted and SP controlled network parts require stronger confidentiality measures such as cryptographic data encryption. This is the case in certain inter-SP VPN scenarios or when the considered SP is on itself a client of a third party network provider. For layer 3 provider-provisioned CE-based VPNs, the SP network does not bare responsibility for confidentiality assurance, as the SP just offers IP connectivity. The confidentiality will then be enforced at the CE and will lie in the tunneling (data separation) or in the cryptographic encryption (e.g., using IPsec) by the CE device. Note that for very sensitive user data (e.g., used in banking operations) the VPN customer may not outsource his data privacy enforcement to a trusted SP. In those situations, PE-to-PE confidentiality will not be sufficient and end-to-end cryptographic encryption will be implemented by the VPN customer on its own private equipment (e.g., using CE-based VPN technologies or cryptographic encryption over the provided VPN connectivity).6.6. User Data and Control Data
An important remark is the fact that both the user data and the VPN control data must be protected. Previous subsections were focused on the protection of the user data, but all the control data (e.g., used to set up the VPN tunnels, used to configure the VFI's or the CE devices (in the context of layer 3 provider-provisioned CE-based VPNs)) will also be secured by the SP to prevent deliberate misconfiguration of provider-provisioned VPNs.6.7. Security Considerations for Inter-SP VPNs
In certain scenarios, a single VPN will need to cross multiple SPs. The fact that the edge-to-edge part of the data path does not fall under the control of the same entity can have security implications, for example with regards to endpoint authentication. Another point is that the SPs involved must closely interact to avoid conflicting configuration information on VPN network elements (such as VFIs, PEs, CE devices) connected to the different SPs.
Appendix A: Optimizations for Tunnel Forwarding
A.1. Header Lookups in the VFIs
If layer 3 PE-based VPNs are implemented in the most straightforward manner, then it may be necessary for PE devices to perform multiple header lookups in order to forward a single data packet. This section discusses an example of how multiple lookups might be needed with the most straightforward implementation. Optimizations which might optionally be used to reduce the number of lookups are discussed in the following sections. As an example, in many cases a tunnel may be set up between VFIs within PEs for support of a given VPN. When a packet arrives at the egress PE, the PE may need to do a lookup on the outer header to determine which VFI the packet belongs to. The PE may then need to do a second lookup on the packet that was encapsulated across the VPN tunnel, using the forwarding table specific to that VPN, before forwarding the packet. For scaling reasons it may be desired in some cases to set up VPN tunnels, and then multiplex multiple VPN-specific tunnels within the VPN tunnels. This implies that in the most straightforward implementation three header lookups might be necessary in a single PE device: One lookup may identify that this is the end of the VPN tunnel (implying the need to strip off the associated header). A second lookup may identify that this is the end of the VPN-specific tunnel. This lookup will result in stripping off the second encapsulating header, and will identify the VFI context for the final lookup. The last lookup will make use of the IP address space associated with the VPN, and will result in the packet being forwarded to the correct CE within the correct VPN.A.2. Penultimate Hop Popping for MPLS
Penultimate hop popping is an optimization which is described in the MPLS architecture document [RFC3031]. Consider the egress node of any MPLS LSP. The node looks at the label, and discovers that it is the last node. It then strips off the label header, and looks at the next header in the packet (which may be an IP header, or which may have another MPLS header in the case that hierarchical nesting of LSPs is used). For the last node on the LSP, the outer MPLS header doesn't actually convey any useful information (except for one situation discussed below).
For this reason, the MPLS standards allow the egress node to request that the penultimate node strip the MPLS header. If requested, this implies that the penultimate node does not have a valid label for the LSP, and must strip the MPLS header. In this case, the egress node receives the packet with the corresponding MPLS header already stripped, and can forward the packet properly without needing to strip the header for the LSP which ends at that egress node. There is one case in which the MPLS header conveys useful information: This is in the case of a VPN-specific LSP terminating at a PE device. In this case, the value of the label tells the PE which LSP the packet is arriving on, which in turn is used to determine which VFI is used for the packet (i.e., which VPN-specific forwarding table needs to be used to forward the packet). However, consider the case where multiple VPN-specific LSPs are multiplexed inside one PE-to-PE LSP. Also, let's suppose that in this case the egress PE has chosen all incoming labels (for all LSPs) to be unique in the context of that PE. This implies that the label associated with the PE-to-PE LSP is not needed by the egress node. Rather, it can determine which VFI to use based on the VPN-specific LSP. In this case, the egress PE can request that the penultimate LSR performs penultimate label popping for the PE-to-PE LSP. This eliminates one header lookup in the egress LSR. Note that penultimate node label popping is only applicable for VPN standards which use multiple levels of LSPs. Even in this case penultimate node label popping is only done when the egress node specifically requests it from the penultimate node.A.3. Demultiplexing to Eliminate the Tunnel Egress VFI Lookup
Consider a VPN standard which makes use of MPLS as the tunneling mechanism. Any standard for encapsulating VPN traffic inside LSPs needs to specify what degree of granularity is available in terms of the manner in which user data traffic is assigned to LSPs. In other words, for any given LSP, the ingress or egress PE device needs to know which LSPs need to be set up, and the ingress PE needs to know which set of VPN packets are allowed to be mapped to any particular LSP. Suppose that a VPN standard allows some flexibility in terms of the mapping of packets to LSPs, and suppose that the standard allows the egress node to determine the granularity. In this case the egress node would need to have some way to indicate the granularity to the ingress node, so that the ingress node will know which packets can be mapped to each LSP.
In this case, the egress node might decide to have packets mapped to LSPs in a manner which simplifies the header lookup function at the egress node. For example, the egress node could determine which set of packets it will forward to a particular neighbor CE device. The egress node can then specify that the set of IP packets which are to use a particular LSP correspond to that specific set of packets. For packets which arrive on the specified LSP, the egress node does not need to do a header lookup on the VPN's customer address space: It can just pop the MPLS header and forward the packet to the appropriate CE device. If all LSPs are set up accordingly, then the egress node does not need to do any lookup for VPN traffic which arrives on LSPs from other PEs (in other words, the PE device will not need to do a second lookup in its role as an egress node). Note that PE devices will most likely also be an ingress routers for traffic going in the other direction. The PE device will need to do an address lookup in the customer network's address space in its role as an ingress node. However, in this direction the PE still needs to do only a single header lookup. When used with MPLS tunnels, this optional optimization reduces the need for header lookups, at the cost of possibly increasing the number of label values which need to be assigned (since one label would need to be assigned for each next-hop CE device, rather than just one label for every VFI). The same approach is also possible when other encapsulations are used, such as GRE [RFC2784] [RFC2890], IP-in-IP [RFC2003] [RFC2473], or IPsec [RFC2401] [RFC2402]. This requires that distinct values are used for the multiplexing field in the tunneling protocol. See section 4.3.2 for detail.Acknowledgments
This document is output of the framework document design team of the PPVPN WG. The members of the design team are listed in the "contributors" and "author's addresses" sections below. However, sources of this document are based on various inputs from colleagues of authors and contributors. We would like to thank Junichi Sumimoto, Kosei Suzuki, Hiroshi Kurakami, Takafumi Hamano, Naoto Makinae, Kenichi Kitami, Rajesh Balay, Anoop Ghanwani, Harpreet Chadha, Samir Jain, Lianghwa Jou, Vijay Srinivasan, and Abbie Matthews. We would also like to thank Yakov Rekhter, Scott Bradner, Dave McDysan, Marco Carugi, Pascal Menezes, Thomas Nadeau, and Alex Zinin for their valuable comments and suggestions.
Normative References
[PPVPN-REQ] Nagarajan, A., Ed., "Generic Requirements for Provider Provisioned Virtual Private Networks (PPVPN)", RFC 3809, June 2004. [L3VPN-REQ] Carugi, M., Ed. and D. McDysan, Ed., "Service Requirements for Layer 3 Provider Provisioned Virtual Private Networks (PPVPNs)", RFC 4031, April 2005.Informative References
[BGP-COM] Sangli, S., et al., "BGP Extended Communities Attribute", Work In Progress, February 2005. [MPLS-DIFF-TE] Le Faucheur, F., Ed., "Protocol extensions for support of Differentiated-Service-aware MPLS Traffic Engineering", Work In Progress, December 2004. [VPN-2547BIS] Rosen, E., et al., "BGP/MPLS VPNs", Work In Progress. [VPN-BGP-OSPF] Rosen, E., et al., "OSPF as the Provider/Customer Edge Protocol for BGP/MPLS IP VPNs", Work In Progress, May 2005. [VPN-CE] De Clercq, J., et al., "An Architecture for Provider Provisioned CE-based Virtual Private Networks using IPsec", Work In Progress. [VPN-DISC] Ould-Brahim, H., et al., "Using BGP as an Auto- Discovery Mechanism for Layer-3 and Layer-2 VPNs," Work In Progress. [VPN-L2] Andersson, L. and E. Rosen, Eds., "Framework for Layer 2 Virtual Private Networks (L2VPNs)", Work In Progress. [VPN-VR] Knight, P., et al., "Network based IP VPN Architecture Using Virtual Routers", Work In Progress, July 2002. [RFC1195] Callon, R., "Use of OSI IS-IS for Routing in TCP/IP and Dual Environments", RFC 1195, December 1990.
[RFC1771] Rekhter, Y. and T. Li, "A Border Gateway Protocol 4 (BGP-4)", RFC 1771, March 1995. [RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G., and E. Lear, "Address Allocation for Private Internets", BCP 5, RFC 1918, February 1996. [RFC1966] Bates, T., "BGP Route Reflection: An alternative to full mesh IBGP", RFC 1966, June 1996. [RFC1997] Chandra, R., Traina, P., and T. Li, "BGP Communities Attribute", RFC 1997, February 2001. [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, October 1996. [RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC2208] Mankin, A., Ed., Baker, F., Braden, B., Bradner, S., O'Dell, M., Romanow, A., Weinrib, A., and L. Zhang, "Resource ReSerVation Protocol (RSVP) Version 1 Applicability Statement Some Guidelines on Deployment", RFC 2208, September 1997. [RFC2210] Wroclawski, J., "The Use of RSVP with IETF Integrated Services", RFC 2210, September 1997. [RFC2211] Wroclawski, J., "Specification of the Controlled-Load Network Element Service", RFC 2211, September 1997. [RFC2212] Shenker, S., Partridge, C., and R. Guerin, "Specification of Guaranteed Quality of Service", RFC 2212, September 1997. [RFC2207] Berger, L. and T. O'Malley, "RSVP Extensions for IPSEC Data Flows", RFC 2207, September 1997. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the Internet Protocol", RFC 2401, November 1998. [RFC2402] Kent, S. and R. Atkinson, "IP Authentication Header", RFC 2402, November 1998.
[RFC2406] Kent, S. and R. Atkinson, "IP Encapsulating Security Payload (ESP)", RFC 2406, November 1998. [RFC2409] Harkins, D. and D. Carrel, "The Internet Key Exchange (IKE)", RFC 2409, November 1998. [RFC2453] Malkin, G., "RIP Version 2", STD 56, RFC 2453, November 1994. [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998. [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, December 1998. [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An architecture for Differentiated Services", RFC 2475, December 1998. [RFC2597] Heinanen, J., Baker, F., Weiss, W., and J. Wroclawski, "Assured Forwarding PHB Group", RFC 2597, June 1999. [RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, G., and B. Palter, "Layer Two Tunneling Protocol 'L2TP'", RFC 2661, August 1999. [RFC2684] Grossman, D. and J. Heinanen, "Multiprotocol Encapsulation Over ATM Adaptation Layer 5", RFC 2684, September 1999. [RFC2685] Fox B. and B. Gleeson, "Virtual Private Networks Identifier," RFC 2685, September 1999. [RFC2746] Terzis, A., Krawczyk, J., Wroclawski, J., and L. Zhang, "RSVP Operation Over IP Tunnels", RFC 2746, January 2000. [RFC2764] Gleeson, B., Lin, A., Heinanen, J., Armitage, G., and A. Malis, "A Framework for IP Based Virtual Private Networks", RFC 2764, February 2000. [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE", RFC 2890, September 2000. [RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000. [RFC2983] Black, D., "Differentiated Services and Tunnels", RFC 2983, October 2000. [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001. [RFC3032] Rosen E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, January 2001. [RFC3035] Davie, B., Lawrence, J., McCloghrie, K., Rosen, E., Swallow, G., Rekhter, Y., and P. Doolan, "MPLS using LDP and ATM VC Switching", RFC 3035, January 2001. [RFC3065] Traina, P., McPherson, D., and J. Scudder, "Autonomous System Confederations for BGP", RFC 3065, June 1996. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3246] Davie, B., Charny, A., Bennet, J.C.R., Benson, K., Le Boudec, J.Y., Courtney, W., Davari, S., Firoiu, V., and D. Stiliadis, "An Expedited Forwarding PHB (Per- Hop Behavior)", RFC 3246, March 2002. [RFC3270] Le Faucheur, F., Wu, L., Davie, B., Davari, S., Vaananen, P., Krishnan, R., Cheval, P., and J. Heinanen, "Multi-Protocol Label Switching (MPLS) Support of Differentiated Services", RFC 3270, May 2002. [RFC3377] Hodges, J. and R. Morgan, "Lightweight Directory Access Protocol (v3): Technical Specification", RFC 3377, September 2002.
Contributors' Addresses
Jeremy De Clercq Alcatel Fr. Wellesplein 1, 2018 Antwerpen, Belgium EMail: jeremy.de_clercq@alcatel.be Bryan Gleeson Nokia 313 Fairchild Drive, Mountain View, CA 94043 USA. EMail: bryan.gleeson@nokia.com Andrew G. Malis Tellabs 90 Rio Robles Drive San Jose, CA 95134 USA EMail: andy.malis@tellabs.com Karthik Muthukrishnan Lucent Technologies 1 Robbins Road Westford, MA 01886, USA EMail: mkarthik@lucent.com Eric C. Rosen Cisco Systems, Inc. 1414 Massachusetts Avenue Boxborough, MA, 01719, USA EMail: erosen@cisco.com Chandru Sargor Redback Networks 300 Holger Way San Jose, CA 95134, USA EMail: apricot+l3vpn@redback.com
Jieyun Jessica Yu University of California, Irvine 5201 California Ave., Suite 150, Irvine, CA, 92697 USA EMail: jyy@uci.eduAuthors' Addresses
Ross Callon Juniper Networks 10 Technology Park Drive Westford, MA 01886-3146, USA EMail: rcallon@juniper.net Muneyoshi Suzuki NTT Information Sharing Platform Labs. 3-9-11, Midori-cho, Musashino-shi, Tokyo 180-8585, Japan EMail: suzuki.muneyoshi@lab.ntt.co.jp
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