Network Working Group M. Bagnulo Internet-Draft A. Garcia-Martinez Expires: July 23, 2004 UC3M January 23, 2004 Multi-Homing Tunnel Broker (MHTB) draft-bagnulo-multi6-mhtb-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on July 23, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract RFC 3178 [1] describes a solution to provide site multi-homing support in IPv6. RFC 3178 multi-homing solution uses tunnels between the different ISPs and the multi-homed site to provide alternative paths in case that one of the exit links is down, protecting the multi-homed site from outages in the direct link with its providers. However, the wide adoption of RFC 3178 multi-homing solution implies the manual configuration of numerous tunnels on the ISPs, which may impose an important workload in ISP network administrators. This note proposes the usage of Multi-Homing Tunnel Brokers to automatically configure the ISP tunnel endpoint in order to ease the adoption of the solution. Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 1] Internet-Draft MHTB January 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Overview of the RFC 3178 Multi-Homing Solution . . . . . . . . 4 3. The Tunnel Broker Model . . . . . . . . . . . . . . . . . . . 6 4. The Multi-Homing Tunnel Broker Service . . . . . . . . . . . . 7 4.1 The Tunnel Broker Service . . . . . . . . . . . . . . . . . . 7 4.2 The Tunnel Server . . . . . . . . . . . . . . . . . . . . . . 8 5. Security Considerations. . . . . . . . . . . . . . . . . . . . 10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . 12 Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 2] Internet-Draft MHTB January 2004 1. Introduction RFC 3178 [1] describes a solution to provide site multi-homing support in IPv6. RFC 3178 multi-homing solution uses tunnels between the different ISPs and the multi-homed site to provide alternative paths in case that one of the exit links is down, protecting the multi-homed site from outages in the direct link with its providers. However, the wide adoption of RFC 3178 multi-homing solution implies the manual configuration of numerous tunnels on the ISPs, which may impose an important workload in ISP network administrators. This note proposes the usage of Multi-Homing Tunnel Brokers to automatically configure the ISP tunnel endpoint in order to ease the adoption of the solution. Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 3] Internet-Draft MHTB January 2004 2. Overview of the RFC 3178 Multi-Homing Solution The mechanism for multi-homing support described in RFC3178 is illustrated in the next figure: +----------------------------------------+ | | | Internet | +----------------------------------------+ | | +----------+ +----------+ |ISPA-PrefA| |ISPB-PrefB| +----------+ +----------+ | | | | | \______________________|___ | | TunnelIA-ERB | || linkA | ______________________/ || linkB | | TunnelIB-ERA || | | || +--------|-|--------------------------||--------+ | +----|-+ +-|---+ | | | ERA | | ERB | | | +------+ +-----+ | | | | Multi-Homed PrefA:Site:: | | Site +------+ PrefB:Site:: | | | Host1| | | +------+ | +-----------------------------------------------+ The multi-homed site has two providers, ISPA and ISPB that have delegated PrefA:Site::/n and PrefB:Site::/m respectively. In the depicted scenario, the multi-homed site has only two providers, but the solution is valid to more general scenarios that include more than 2 providers. It is assumed that hosts within the multi-homed site configure at least one address per provider's prefix obtained. In order to obtain fault tolerance capabilities, RFC 3178 proposes the creation of two tunnels: - TunnelIA-ERB: from the ISPA's router to site exit router ERB Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 4] Internet-Draft MHTB January 2004 - TunnelIB-ERA: from the ISPB's router to site exit router ERA The resulting behaviour is that when one of the two exit links fails, packets are routed through the correspondent tunnel. That is, if linkA(linkB) fails, packets arriving to ISPA(ISPB) addressed to PrefA:Site::/n(PrefB:Site::/m) are routed through TunnelIA-ERB (TunnelIB-ERA) to the multi-homed end site. This configuration provides fault tolerance capabilities, including the preservation of established communications, when one of the site exit links fails. Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 5] Internet-Draft MHTB January 2004 3. The Tunnel Broker Model RFC 3053 [2] presents a general tunnel broker model and its particular application to the creation of IPv6 over IPv4 tunnels for the Internet's transition to IPv6. Since the tunnels used in RFC 3178 are IPv6 in IPv6 tunnels used for redundancy, the particular implementation details will differ in the two configurations. However, the general model of the tunnel broker presented in RFC 3053 can still be applied to the multi-homing environment. The tunnel broker model presented in RFC 3053 is illustrated in the next figure and it consists in the following components: - The Tunnel Broker (TB) is the element to which the end-users connect themselves to create, modify and delete tunnels. Then the TB communicates with one or several Tunnel Servers to actually create the tunnels requested by the users. - The Tunnel Server (TS) is the server's tunnel endpoint that is created, modified or deleted upon reception of a request from the TB. Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 6] Internet-Draft MHTB January 2004 4. The Multi-Homing Tunnel Broker Service In order to provide a Tunnel Broker Service for the RFC3178 multi-homing solution, both a Tunnel Broker and one or more Tunnel Servers are needed. 4.1 The Tunnel Broker Service The TB will receive user requests to create tunnels. Potential users are all the clients of the ISP. We assume that the ISP clients have a commercial relationship with the ISP, so that the ISP can identify its clients and the prefix that the ISP has assigned to them. We also assume that, because of the existent business relationship between the ISP and its customer, the ISP has created the appropriate means to identify its clients through the network, such as a user name and a password or a public key certificate. So, the ISP customer will send a tunnel creation request to the TB. The TB can accept requests through different type of interfaces, for instance the TB can accept request submitted through http. Clients submitting requests have to properly identify themselves through existent means. The requests have to contain at least the following information: - Client identification. - The IPv6 address of the client side endpoint of the tunnel. - The IPv6 prefix for which a backup route through the tunnel will be created. - Request authorization information generated through available means, such as client's password or client's private/public key plus certificate. Upon the reception of a request the TB will: - Verify client identity. - Verify authorization information. - Verify that the prefix included in the request is contained in the address range that the ISP has delegated to this particular client. - Send configuration order to the appropriate TS to configure the requested tunnel. Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 7] Internet-Draft MHTB January 2004 - Inform the client of the IP address of the endpoint of ISP side of the tunnel. 4.2 The Tunnel Server The Tunnel Server service can be placed in different devices within the ISP network. An option is to use the exit router connecting the ISP to the client as the tunnel server. In this case, packets will always be forwarded to this exit router, and if the route through the direct link is not available, the exit router will forward the packets through the tunnel interface. This option requires the TB to be capable of communicating with the exit routers through the protocol selected for the task (rsh, smnp, others). +----------------------------------------+ | | | Internet | +----------------------------------------+ | | +----------------------+ +-----+ |ISPA-PrefA | |ISPB | | | |PrefB| | +---+ | +-----+ | |TB | route to | | | +---+ PrefA:Site::| | | | ^ | | | v | | | | | +----+ | | | ->->->->->|IAER| | | | tunnel conf +----+ | | +----------------|-|---+ | | | | | \_______________ | | TunnelIA-ERB || | || | || +--------|-----------------||--------+ | +-----+ +-|---+ | | | ERA | | ERB | | | +-----+ +-----+ | | | | Multi-Homed PrefA:Site:: | | Site PrefB:Site:: | | | +------------------------------------+ Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 8] Internet-Draft MHTB January 2004 Another option is to place specific TS devices. In this case, the TB will configure the tunnel in this specific TS device. The TS will then, upon the reception of this configuration orders, create the tunnel and will also start announcing the clients prefix through a route with a preference lower than the one contained in the route announced by the exit router. +----------------------------------------+ | | | Internet | +----------------------------------------+ | | +-----------------------+ +-----+ |ISPA-PrefA | |ISPB | | | |PrefB| | +---+ +---+ | +-----+ | |TS |-----------|TB | | | | +---+tunnel conf+---+ | | | | | | | v route | | | route PrefA:Site| | | PrefA:Site pref high | | | pref low ^ | | | | | | | +----+ | | | |IAER| | | | +----+ | | +----------------|-|----+ | | | | | \_______________ | | TunnelIA-ERB || | || | || +--------|-----------------||--------+ | +-----+ +-|---+ | | | ERA | | ERB | | | +-----+ +-----+ | | | | Multi-Homed PrefA:Site:: | | Site PrefB:Site:: | | | +------------------------------------+ Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 9] Internet-Draft MHTB January 2004 5. Security Considerations. This note proposes a Tunnel Broker service to simplify the management of tunnels used to provide multi-homing support as specified by RFC 3178. The creation, modification and deletion of tunnels as well as the injection of the required routes are operations that affect the ISP critical infrastructure as it is the internal routing fabric. So, proper security mechanism has to be adopted in order to prevent potential attacks. The following communications have to be secured: - Communication between the client and the Tunnel Broker: it is assumed that the ISP has a mechanism to properly identify the client. Possible options are user name and password or private/public key pair and certificate. The request sent by the client to the Tunnel Broker have to contain authorization information based on this identification information. - Communication between the Tunnel Broker and the Tunnel Server. As specified in RFC 3053, this is a critical communication that has to be properly secured. Since it is a communication between two devices of the ISP, the particular security mechanism used by the ISP is out of the scope of this document. Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 10] Internet-Draft MHTB January 2004 References [1] Hagino, J. and H. Snyder, "IPv6 Multihoming Support at Site Exit Routers", RFC 3178, October 2001. [2] Durand , A., Fasano , P., Guardini , I. and D. Lento , "IPv6 Tunnel Broker", RFC 3053, January 2001. Authors' Addresses Marcelo Bagnulo Universidad Carlos III de Madrid Av. Universidad 30 Leganes, Madrid 28911 SPAIN Phone: 34 91 6249500 EMail: marcelo@it.uc3m.es URI: http://www.it.uc3m.es Alberto Garcia-Martinez Universidad Carlos III de Madrid Av. Universidad 30 Leganes, Madrid 28911 SPAIN Phone: 34 91 6249500 EMail: alberto@it.uc3m.es URI: http://www.it.uc3m.es Bagnulo & Garcia-Martinez Expires July 23, 2004 [Page 11] Internet-Draft MHTB January 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property 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; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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