Network Working Group Naiming Shen Internet-Draft Cisco Systems Intended status: Informational Track March 2007 Expires: September 2007 Interface Based Point-to-Point Neighbor BFD draft-shen-bfd-intf-p2p-nbr-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This document expires in September 26, 2007. Abstract This document describes an application of Bidirectional Forwarding Detection (BFD) protocol named Interface Based Point-to-Point Neighbor BFD. This mechanism can be used to simplify the BFD operations over point-to-point physical and logical links in networks. 1. Conventions Used In This Document 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 RFC2119 [12]. Shen Expires September 2007 [Page 1] Internet-Draft INTF-P2P Neighbor BFD March 2007 2. Introduction Point-to-point circuit type is commonly used in networks. With increasingly popularity of Ethernet technology, many networks deploy it in a point-to-point fashion. It is widely used by connecting systems back-to-back (physical point-to-point), or through switches with vLAN configuration (logical point-to-point). Point-to-point circuit on Ethernet brings many benefits such as QoS applications, TE bandwidth reservation, simplified routing operations [1] and so on. BFD [2][3] is developed to detect faults in the bidirectional path between two network elements, and it has been widely accepted and deployed in IP networks which require routing and forwarding convergence in very low latency. This document describes a special application for BFD over point-to-point physical or logical circuits. This application is not a normal BFD client such as upper layer routing protocol, but it is a management element for circuit itself where BFD is required and configured. This circuit or interface management element will change the state of the point-to-point circuit or interface base on states of BFD. All the upper layer routing protocols get fast convergence notification through the circuit or interface state change regardless whether they have BFD direct interaction or not. The benefits of this proposal include fast development and rollout of BFD services; no complex handling for protocols such as RIP and static routing; simpler configuration and management on the routers or other network related elements; and minimized BFD session numbers on the network devices where multiple address families, multiple routing instances, multiple routing areas, multiple routing topologies, or multiple IP/IPv6 subnets could exist on the interfaces. 3. Applications and Limitations The INTF-P2P Neighbor BFD application is to provide fast point-to-point link down detection for the routing protocols and services over the link. All the protocols do not have to interact directly with BFD, rather they will interact with interface as they normally do. Fast link down BFD notification is relayed from interface management through interface state into routing protocols. This application is only applied over point-to-point physical and logical interfaces. This application MUST NOT be used for point-to-multipoint circuits or having multiple neighbors over broadcast interfaces. Shen Expires September 2007 [Page 2] Internet-Draft INTF-P2P Neighbor BFD March 2007 The INTF-P2P Neighbor BFD application only establish one BFD session over a point-to-point link. It can be either IPv4 or IPv6 BFD session. The peering address of the session SHOULD be explicitly configured on the interface to bootstrap. The configuration of local end point SHOULD be optional, it is normally the local interface address. This application SHOULD NOT be used in the the environment where liveness of the link requires to be data protocol and forwarding state dependent. For example, if a router implements BFD for IPv4 and IPv6 on two different hardware service modules or in two different software processes, obviously one protocol BFD session goes down does not automatically imply the other one also has problem. But even in that case, it might be better off to re-route the other protocol traffic at the same time if there are alternative paths available. This will be operator's decision whether to use INTF-P2P Neighbor BFD with such a network device. The base specifications of BFD define the bits on the wire and the state machines of the protocol. How the BFD packet sharing the common forwarding fate with data packet is very much implementation specific. The protocol itself does not guarantee the forwarding plane for the data packets are exercised even both IPv4 and IPv6 sessions are established over an interface. Again, INTF-P2P Neighbor BFD SHOULD NOT be used if the network requires the BFD sessions completely exercising the data forwarding plane. If the main concern of a network is the physical or link layer connection, then INTF-P2P Neighbor BFD offers a simpler solution while using the well established BFD infrastructure and mechanism. Since the INTF-P2P Neighbor BFD can change the interface state, it not only can offer BFD service to all the IPv4 and IPv6 protocols, it also can offer BFD service to any legacy or future new protocols as long as they rely on the interface state. 4. Interface Based P2P Neighbor BFD INTF-P2P Neighbor BFD is an application of BFD [3], the client is the interface where BFD service is required. Configuration is needed under the interface(point-to-point) to specify the peer address which can be either an IPv4 or IPv6 address. The interface needs to be IPv4 and/or IPv6 enabled. The BFD session and operation should be established and run as normal, there is no change at all to the BFD specifications. Thus there is no compatibility issue when one side of the link runs INTF-P2P Neighbor BFD and the other side is running BFD with other routing applications or clients registered. When this BFD session state changes from UP to DOWN, the INTF-P2P Neighbor BFD client SHOULD immediately bring down the point-to-point interface where the BFD is configured on. Shen Expires September 2007 [Page 3] Internet-Draft INTF-P2P Neighbor BFD March 2007 It will set up a timer with a predetermined value, for example with 5 seconds interface hold-down. During this interface hold-down period, there will be no packet to be sent or received on this interface. When this timer expires, the INTF-P2P Neighbor BFD client will try to bring up this interface, assume the other conditions are met for the interface to be in the UP state. It will also set a flag on the interface to indicate the INTF-P2P Neighbor BFD session is still down at the moment. This special flag will only be used by protocols like static routing process which will be described in section 4.2. BFD over this interface should try to re-establish the session when the interface is back in UP state. As soon as the BFD session comes to UP state, it SHOULD clear the flag set on the interface and also have the static routing to re-evaluate the routes pointing to this interface as next-hop. Since INTF-P2P Neighbor BFD is only meant to operate in the point-to-point environment, an implementation SHOULD deploy a mis-configuration detection scheme on the broadcast interface both at the time of configuration and with periodical checks, as long as the BFD is in UP state. One simple mechanism could be to walk through the ARP/ND cache tables of this interface to detect if there exist dynamically learned entries which contain different MAC addresses. It then SHOULD send out a warning about the multiple peers existing on the interface, and optionally abort the INTF-P2P Neighbor BFD operation over this interface until the configuration error is corrected. 4.1 Dynamic Routing Protocols Since the INTF-P2P Neighbor BFD will bring down the interface when it's BFD session going down, some routing protocols such as IS-IS [4][5], OSPF [6][7] will tear down their adjacencies and reroute immediately, assume the initial hold-down timer is not applied. Other routing protocols such as RIP [8, 9], BGP [10] will be updated by the RIB table processes about the interface state or their recursive next-hop changes. Protocols will try to reroute around the failed point-to-point link. When the interface comes back up, protocols will try to establish the adjacencies or advertise their routes, this part is the normal protocol operation regardless of whether the INTF-P2P Neighbor BFD is in use. There is no protocol level change to any of the dynamic routing protocols from this proposal. The dynamic routing protocols do not pay attention to the special flag on interface mentioned above. 4.2 Static Routing Instances The going down portion is similar to the dynamic routing protocols described in the above section. In the bring up part, the static routing instances need to pay attention Shen Expires September 2007 [Page 4] Internet-Draft INTF-P2P Neighbor BFD March 2007 to the special flag set by INTF-P2P Neighbor BFD. Thus the interface DOWN state for static routing should be either the interface is traditionally DOWN, or the special BFD flag is set. When the INTF-P2P Neighbor BFD session is up, it informs the static routing about the interface is UP (again) and static routes can be installed into RIB tables this time since the special BFD flag on the interface is cleared. 4.3 Fast Re-Route MPLS TE FRR [11] and other IP and MPLS fast re-route schemes can be triggered in respond to BFD session state going down. When INTF-P2P Neighbor BFD is used over the interface, the interface DOWN state can simply trigger the fast reroute action even there is no direct signaling between the BFD and FRR module. 5. Security Considerations This document does not introduce any additional security issue beyond those already considered in the base BFD specifications. 6. IANA Considerations This document has no IANA considerations. 7. Acknowledgement The author would like to thank Dave Katz and David Ward for their comments on the architecture and implementation part of the BFD operations in this document. 8. References [1] Shen, N., Zinin, A., "Point-to-point operation over LAN in link-state routing protocols", draft-ietf-isis-igp-p2p-over-lan-06.txt, work in progress. [2] Katz, D., Ward, D., "Bidirectional Forwarding Detection", draft-ietf-bfd-base-06.txt, work in progress. [3] Katz, D., Ward, D., "BFD for IPv4 and IPv6 (Single Hop)", draft-ietf-bfd-v4v6-1hop-06.txt, work in progress. [4] ISO, "Intermediate system to Intermediate system routing information exchange protocol for use in conjunction with the Protocol for providing the Connectionless-mode Network Service (ISO 8473)," ISO/IEC 10589:1992. Shen Expires September 2007 [Page 5] Internet-Draft INTF-P2P Neighbor BFD March 2007 [5] Hopps, C., "Routing IPv6 with IS-IS", draft-ietf-isis-ipv6-06.txt, work in progress. [6] Moy, J., "OSPF Version 2", RFC 2328, April 1998. [7] Coltun, R., Ferguson, D., and J. Moy, "OSPF for IPv6", July 1998. [8] Hedrick, C., "Routing Information Protocol", RFC 1058, June 1988. [9] Malkin, G., Minnear, R., "RIPng for IPv6", RFC 2080, January 1997. [10] Rekhter, Y., Li, T., Hares, S., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, January 2006. [11] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May 2005. [12] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 9. Author's Addresses Naiming Shen Cisco Systems 225 West Tasman Drive San Jose, CA 95134 USA Email: naiming@cisco.com IPR Disclaimer 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 assurances of licenses to be made available, or the result of an 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. Shen Expires September 2007 [Page 6] Internet-Draft INTF-P2P Neighbor BFD March 2007 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. Full Copyright Notice Copyright (C) The IETF Trust (2007). 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, THE IETF TRUST 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. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Shen Expires September 2007 [Page 7]