--- 1/draft-ietf-bfd-v4v6-1hop-03.txt 2006-02-04 17:19:11.000000000 +0100 +++ 2/draft-ietf-bfd-v4v6-1hop-04.txt 2006-02-04 17:19:11.000000000 +0100 @@ -1,19 +1,19 @@ Network Working Group D. Katz Internet Draft Juniper Networks D. Ward Cisco Systems -Expires: January, 2006 July, 2005 +Expires: April, 2006 October, 2005 BFD for IPv4 and IPv6 (Single Hop) - draft-ietf-bfd-v4v6-1hop-03.txt + draft-ietf-bfd-v4v6-1hop-04.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 @@ -45,21 +45,21 @@ 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 RFC-2119 [KEYWORDS]. 1. Introduction One very desirable application for BFD [BFD] is to track IPv4 and IPv6 connectivity between directly-connected systems. This could be - used to supplant the detection mechanisms in IS-IS and OSPF, or to + used to supplement the detection mechanisms in IS-IS and OSPF, or to monitor router-host connectivity, among other applications. This document describes the particulars necessary to use BFD in this environment, and describes how BFD can be used in conjunction OSPFv2 [OSPFv2], OSPFv3 [OSPFv3], and IS-IS [ISIS]. 2. Applications and Limitations This application of BFD can be used by any pair of systems communicating via IPv4 and/or IPv6 across a single IP hop that can be @@ -101,23 +101,23 @@ demultiplexing incoming BFD Control packets, but ultimately the mechanisms in [BFD] MUST be used to demultiplex incoming packets to the proper session. BFD Echo packets MUST be transmitted in UDP packets with destination UDP port 3785 in an IPv4 packet. The setting of the UDP source port is outside the scope of this specification. The destination address MUST be chosen in such a way as to cause the remote system to forward the packet back to the local system. The source address MUST be chosen in such a way as to preclude the remote system from generating - ICMP Redirect messages (in particular, the source address MUST NOT be - part of the subnet bound to the interface over which the BFD Echo - packet is being transmitted.) + ICMP Redirect messages. In particular, the source address MUST NOT + be part of the subnet bound to the interface over which the BFD Echo + packet is being transmitted. 4.2. BFD for IPv6 In the case of IPv6, BFD Control packets MUST be transmitted in UDP packets with destination port 3784, within an IPv6 packet. The source port MUST be in the range 49152 through 65535. The same UDP source port number MUST be used for all BFD Control packets associated with a particular session. The source port number SHOULD be unique among all BFD sessions on the system. If more than 16384 BFD sessions are simultaneously active, UDP source port numbers MAY @@ -177,26 +177,27 @@ changed, so that the application might choose to change the destination address or take some other action. Note that the TTL/Hop Count check described in section 5 (or the use of authentication) precludes the BFD packets from having come from any source other than the immediate neighbor. 7. BFD for use with OSPFv2, OSPFv3, and IS-IS The two versions of OSPF, as well as IS-IS, all suffer from an architectural limitation, namely that their Hello protocols are - limited in the granularity of failure their detection times. In + limited in the granularity of their failure detection times. In particular, OSPF has a minimum detection time of two seconds, and IS- IS has a minimum detection time of one second. BFD MAY be used to achieve arbitrarily small detection times for - these protocols by supplanting the Hello protocols used in each case. + these protocols by supplementing the Hello protocols used in each + case. It should be noted that the purpose of using BFD in this context is not to replace the adjacency timeout mechanism, nor is it to demonstrate that the network is fully functional for the use of the routing protocol, but is simply to advise the routing protocol that there are problems forwarding the data protocol for which the routing protocol is calculating routes. 7.1. Session Establishment @@ -259,21 +260,26 @@ be established, and, more particularly, data cannot be forwarded. To avoid this situation, it would be beneficial to not allow the IGP to establish a neighbor/adjacency. However, this would preclude the operation of the IGP in an environment in which not all systems support BFD. Therefore, if a BFD session is not in Up state (possibly because the remote system does not support BFD), it is OPTIONAL to preclude the establishment of an OSPF neighbor or an IS-IS adjacency. The choice of whether to do so SHOULD be controlled by means outside the scope - of this specification, such as configuration or other mechanisms. + of this specification, such as configuration or other mechanisms. If + an OSPF neighbor or IS-IS adjacency is established but the + corresponding BFD session is not in Up state (implying that the + neighbor does not support BFD) implementations MAY raise the BFD + transmit interval beyond the minimum of one second in order to + minimize extraneous traffic. 7.4. Interactions with OSPF and IS-IS with Graceful Restart The Graceful Restart functions in OSPF [OSPF-GRACE] and IS-IS [ISIS- GRACE] are predicated on the existence of a separate forwarding plane that does not necessarily share fate with the control plane in which the routing protocols operate. In particular, the assumption is that the forwarding plane can continue to function while the protocols restart and sort things out. @@ -358,21 +365,21 @@ A number of mechanisms are available to tunnel IPv4 and IPv6 over arbitrary topologies. If the tunnel mechanism does not decrement the TTL or hop count of the network protocol carried within, the mechanism described in this document may be used to provide liveness detection for the tunnel. The BFD Authentication mechanism SHOULD be used and is strongly encouraged. Normative References [BFD] Katz, D., and Ward, D., "Bidirectional Forwarding Detection", - draft-ietf-bfd-base-03.txt, July, 2005. + draft-ietf-bfd-base-04.txt, October, 2005. [BFD-MULTI] Katz, D., and Ward, D., "BFD for Multihop Paths", draft- ietf-bfd-multihop-03.txt, July, 2005. [GTSM] Gill, V., et al, "The Generalized TTL Security Mechanism (GTSM)", RFC 3682, February 2004. [ISIS] Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual environments", RFC 1195, December 1990. @@ -422,21 +429,23 @@ Dave Ward Cisco Systems 170 W. Tasman Dr. San Jose, CA 95134 USA Phone: +1-408-526-4000 Email: dward@cisco.com Changes from the previous draft - All changes are editorial in nature. + Text was added to point out that implementations may raise the BFD + transmit interval above the minimum if it appears that the neighbor + does not support BFD. All other changes are editorial in nature. 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 @@ -469,11 +478,11 @@ 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. - This document expires in January, 2006. + This document expires in April, 2006.