Internet Engineering Task Force T. Tsou, Ed. Internet-Draft Huawei Technologies (USA) Intended status: Informational March 23, 2012 Expires: September 24, 2012 BFD Support DS-Lite draft-tsou-bfd-ds-lite-02 Abstract In DS-Lite, the tunnel is not associated with any state information, which makes it difficult to manage and diagnose. Some tools may be used to resolve this problem. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on September 24, 2012. Copyright Notice Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Tsou Expires September 24, 2012 [Page 1] Internet-Draft BFD DS-Lite March 2012 Table of Contents 1. Problem statement . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Solutions . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. BFD . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1.1. DS-Lite Scenario . . . . . . . . . . . . . . . . . . . 4 3.1.2. Parameters for BFD . . . . . . . . . . . . . . . . . . 4 3.1.3. Procedures . . . . . . . . . . . . . . . . . . . . . . 5 3.1.4. Implementation Considerations . . . . . . . . . . . . . 5 3.2. PCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.3. PING . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4. Failover . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8 Tsou Expires September 24, 2012 [Page 2] Internet-Draft BFD DS-Lite March 2012 1. Problem statement In DS-Lite [RFC6333], the IPv4-in-IPv6 tunnel is stateless, no status information about tunnel is available, and no keep-alive mechanism is available. It is difficult to know whether the tunnle is up or down, which creates a problem for operation and maintenance. If a B4 can detect a failure in the link to AFTR, it can switch to another AFTR, setup new tunnel to that AFTR, so as to continue the network service. Anycast could be used for the same purpose -- failover, but there is an ICMP error message problem, that is, when a packet is sent from AFTR to B4, one of the routers along the path may generate an error ICMP message, e.g., packet too big, and the error message is not sent back to the source AFTR, but sent to another AFTR. In some cases, the operators may want to have some more diagnostic functions besides connectivity test, e.g. delay and throughput test, this may be useful if the operator is providing services like IPTV and video conference. ETHOAM and BFD can provide these functionalities. But ETHOAM[802.1ag - 2007]is for ethernet layer2; and BFD OAM functions now is only available for MPLS-TP[RFC6374]. This is currently out of the scope of this spec. 1.1. Requirements Language 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 [RFC2119]. 2. Terminology AFTR: Address Family Transition Router. B4: Basic Bridging BroadBand. BFD: Bidirectional Forwarding Detection. CPE: Customer Premise Equipment (i.e., the DS-Lite B4). FQDN Fully Qualified Domain Name. PCP Port Control Protocol. Tsou Expires September 24, 2012 [Page 3] Internet-Draft BFD DS-Lite March 2012 3. Solutions 3.1. BFD BFD is a mechanism intended to detect faults in the bidirectional path. It is usually used in conjunction with applications like OSPF, IS-IS, etc, for fast fault recovery/fast re-route. [RFC5882] BFD [RFC5880]can be used in DS-Lite, by creating a BFD session between the B4 and the AFTR to provide tunnel status information. If a fault is detected the B4 can try to create a DS-Lite tunnel with another AFTR and terminate the existing one, so as to continue network service. [I-D.vinokour-bfd-dhcp]proposes using a DHCP option to distribute BFD parameters to the B4. But in case of DS-Lite, some of the key BFD parameters are already available (e.g., peer IP address is already available), and other parameters can be negotiated by BFD signaling or statically configured, so that no extra DHCP option(s) need to be defined. 3.1.1. DS-Lite Scenario In DS-Lite [RFC6333], the BFD packet SHOULD be sent through an IPv4- in-IPv6 tunnel, as shown in Figure 1. The IPv4 addresses of the B4 and AFTR SHOULD be the endpoints of a BFD session. +--------------+ +--------------+ +------+ | | +------+ | | | |-----+--------------+-----| | | | | CPE | IPv6 Tunnel | AFTR |-----| IPv4 Network | | (B4) |-----+--------------+-----| | | | +------+ | IPv6 Network | +------+ | | 192.0.0.2 +--------------+ 192.0.0.1 +--------------+ Figure 1: DS-Lite Scenario 3.1.2. Parameters for BFD In order to set up a BFD session, the following parameters are needed, as shown in Section 4.1 of[RFC5880]: o Peer IP address o My Discriminator o Your Discriminator Tsou Expires September 24, 2012 [Page 4] Internet-Draft BFD DS-Lite March 2012 o Desired Min TX Interval o Required Min RX Interval o Required Min Echo RX Interval In DS-Lite [RFC6334], the B4 WAN-side IPv4 address is a well-known address 192.0.0.2, and the AFTR's IPv4 address is 192.0.0.1, as defined in section 5.7 of[RFC6333]. Because all the B4s and AFTRs use the same well-known IP addresses, IPv4 addresses are not sufficient for setting up a BFD session. From the B4's point of view, the B4 needs to create an IPv6 tunnel to an AFTR so as to get network connectivity to the AFTR, and send IPv4 BFD packets through the tunnel to manage it. The other parameters listed above can be negotiated by BFD signaling, and initial values can be configured on the B4 and AFTR. 3.1.3. Procedures In DS-Lite [RFC6333], when a B4 gets online, it will be assigned an IPv6 prefix/address, and also the FQDN of the AFTR, as defined in [RFC6334]. The B4 will create an IPv6 tunnel to the AFTR with which, along with the well known B4 IPv4 address 192.0.0.2 and AFTR IPv4 address 192.0.0.1, the B4 can initiate a BFD session to the AFTR. BFD packets will be sent through DS-Lite tunnel. As defined in section 4 of [RFC5881], BFD control packet MUST be sent in UDP packet with destination port 3784, and BFD echo packet MUST be sent in UDP packet with destination port 3785. When sending out the first BFD packet, the B4 can generate a unique local discriminator, and set the remote discriminator to zero. When the AFTR receive the first BFD packet from a B4, the AFTR will also generate a corresponding local discriminator, and put it in the response packet to the B4. This will finish the discriminator negotiation in the B4 to AFTR direction, without any manual configuration. When the AFTR receives the first packet from a B4, AFTR will get the IPv6 address and discriminator of the B4, so that the AFTR can initiate the BFD session in the other direction and a similar discriminator negotiation can be carried out. 3.1.4. Implementation Considerations BFD is usually used for quick fault detection, at a very small time scale, e.g. milliseconds. But in DS-Lite, it may not be necessary to detect faults in such a short time. On the other hand, an AFTR may Tsou Expires September 24, 2012 [Page 5] Internet-Draft BFD DS-Lite March 2012 need to support tens of thousands of B4s, which means the AFTR will need to support the same number of BFD sessions. In order to meet performance requirements on the AFTR, it may be necessary to extend the time period between BFD packet transmissions to a longer time, e.g., 10s or 30s. 3.2. PCP PCP [I-D.ietf-pcp-base-23] is a NAT traversal tool, and it can also be used for network connectivity test if PCP is supported in the network. A common use case of PCP is to create pinhole so that external users can visit the serviers located behind a NAT, and the lifetime of the pinhole mapping is usually long, e.g. hours, and the lifetime will be refreshed periodically by the client before it is expired. For the purpose of network connectivity test, B4 can create a mapping in the CGN via PCP, with short life time, e.g. 10s of seconds, and keep on refreshing the mapping before it is expired. If any refresh request fail, B4 knows that something is wrong with the link or the PCP server or CGN. In order to detect the network connectivity of the DS-Lite tunnel, the encapsulation mode MUST be used for PCP -- PCP packets are sent through DS-Lite tunnel. Encapsulation mode and plain mode are two alternatives for PCP, there is no concensus yet which one should be prefered in the PCP spec. 3.3. PING PING is a common tool used for network node reachability tes, most of the network nodes provide this tool. In case of DS-Lite, B4 can send PING packets to AFTR periodically. If B4 does not receive response packets for a certain number of PING request packet, e.g. 3, then B4 decides that a fault is detected. In order to test the connectivity of DS-Lite tunnel, PING packets MUST be sent using ICMPv4, rather than ICMPv6. BFD can provide more diagnostic functions than PING, as depicted in section 4.1 of [RFC5880]. 4. Failover The FQDN of the AFTR is sent to B4 via a DHCP option, as defined in [RFC6334]. Multiple IP addresses can be configured for an FQDN on the DNS server. If B4 detect a failure on the link to AFTR, B4 MUST terminate the current DS-Lite tunnel, choose another AFTR address in the list, and create a tunnel to the new AFTR. B4 SHOULD also re- Tsou Expires September 24, 2012 [Page 6] Internet-Draft BFD DS-Lite March 2012 configure the connectivity test tool accordingly if necessary, and restart the test procedures. 5. IANA Considerations This memo includes no request to IANA. 6. Security Considerations In DS-Lite [RFC6333], the B4 may not be directly connected to the AFTR; there may be other routers between them. Then there are potential spoofing problems, as described in [RFC5883]. Hence cryptographic authentication SHOULD be used as described in [RFC5880] if security is concerned. 7. Acknowledgements The author would like to thank Mohamed Boucadair for his useful comments, more solutions are included in this memo. 8. References 8.1. Normative References [I-D.ietf-pcp-base-23] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P. Selkirk, "Port Control Protocol (PCP)(work in progress)", Feb 2012. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD)", RFC 5880, June 2010. [RFC5881] Katz, D. and D. Ward, "Bidirectional Forwarding Detection (BFD) for IPv4 and IPv6 (Single Hop)", RFC 5881, June 2010. [RFC5882] Katz, D. and D. Ward, "Generic Application of Bidirectional Forwarding Detection (BFD)", RFC 5882, June 2010. [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection Tsou Expires September 24, 2012 [Page 7] Internet-Draft BFD DS-Lite March 2012 (BFD) for Multihop Paths", RFC 5883, June 2010. [RFC6333] Durand, A., Droms, R., Woodyatt, J., and Y. Lee, "Dual- Stack Lite Broadband Deployments Following IPv4 Exhaustion", RFC 6333, August 2011. [RFC6334] Hankins, D. and T. Mrugalski, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Option for Dual-Stack Lite", RFC 6334, August 2011. [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay Measurement for MPLS Networks", RFC 6374, September 2011. 8.2. Informative References [802.1ag - 2007] IEEE Computer Societ, "IEEE Standard for Local and Metropolitan Area Networks - Virtual Bridged Local Area Networks Amendment 5: Connectivity Fault Management", 2007. [I-D.vinokour-bfd-dhcp] Vinokour, V., "Configuring BFD with DHCP and Other Musings", May 2008. Author's Address Tina Tsou (editor) Huawei Technologies (USA) 2330 Central Expressway Santa Clara CA 95050 USA Phone: +1 408 330 4424 Email: tina.tsou.zouting@huawei.com Tsou Expires September 24, 2012 [Page 8]