--- 1/draft-ietf-bfd-v4v6-1hop-07.txt 2008-03-24 23:12:18.000000000 +0100 +++ 2/draft-ietf-bfd-v4v6-1hop-08.txt 2008-03-24 23:12:18.000000000 +0100 @@ -1,19 +1,19 @@ Network Working Group D. Katz Internet Draft Juniper Networks D. Ward Cisco Systems -Expires: July, 2008 January, 2008 +Expires: September, 2008 March, 2008 BFD for IPv4 and IPv6 (Single Hop) - draft-ietf-bfd-v4v6-1hop-07.txt + draft-ietf-bfd-v4v6-1hop-08.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 @@ -51,21 +51,21 @@ to monitor router-host connectivity, among other applications. This document describes the particulars necessary to use BFD in this environment. Interactions between BFD and other protocols and system functions are described in the BFD Generic Applications document [BFD-GENERIC]. 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 + communicating via IPv4 and/or IPv6 across a single IP hop that is associated with an incoming interface. This includes, but is not limited to, physical media, virtual circuits, and tunnels. Each BFD session between a pair of systems MUST traverse a separate path in both directions. If BFD is to be used in conjunction with both IPv4 and IPv6 on a particular link, a separate BFD session MUST be established for each protocol (and thus encapsulated by that protocol) over that link. @@ -97,23 +97,24 @@ 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 + ICMP Redirect messages. In particular, the source address SHOULD NOT be part of the subnet bound to the interface over which the BFD Echo - packet is being transmitted. + packet is being transmitted, unless it is known by other means that + the remote system will not send Redirects. 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 @@ -124,95 +125,95 @@ 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 IPv6 packet. The setting of the UDP source port is outside the scope of this specification. The source and destination addresses MUST both be associated with the local system. 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. -5. TTL/Hop Count Issues +5. TTL/Hop Limit Issues If BFD authentication is not in use on a session, all BFD Control - packets for the session MUST be sent with a TTL or Hop Count value of + packets for the session MUST be sent with a TTL or Hop Limit value of 255. All received BFD Control packets that are demultiplexed to the - session MUST be discarded if the received TTL or Hop Count is not + session MUST be discarded if the received TTL or Hop Limit is not equal to 255. A discussion of this mechanism can be found in [GTSM]. If BFD authentication is in use on a session, all BFD Control packets - MUST be sent with a TTL or Hop Count value of 255. All received BFD + MUST be sent with a TTL or Hop Limit value of 255. All received BFD Control packets that are demultiplexed the session MAY be discarded - if the received TTL or Hop Count is not equal to 255. + if the received TTL or Hop Limit is not equal to 255. In the context of this section, "authentication in use" means that the system is sending BFD control packets with the Authentication bit set and with the Authentication Section included, and that all unauthenticated packets demultiplexed to the session are discarded, per the BFD base specification. 6. Addressing Issues - On a subnetted network, BFD Control packets MUST be transmitted with - source and destination addresses that are part of the subnet - (addressed from and to interfaces on the subnet.) + Implementations MUST ensure that all BFD Control packets are + transmitted over the one-hop path being protected by BFD. - On an addressed but unsubnetted point-to-point link, BFD Control - packets MUST be transmitted with source and destination addresses - that match the addresses configured on that link. + On a multiaccess network, BFD Control packets MUST be transmitted + with source and destination addresses that are part of the subnet + (addressed from and to interfaces on the subnet.) - On an unnumbered point-to-point link, the source address of a BFD - Control packet MUST NOT be used to identify the session. This means - that the initial BFD packet MUST be accepted with any source address, - and that subsequent BFD packets MUST be demultiplexed solely by the - My Discriminator field (as is always the case.) This allows the - source address to change if necessary. If the received source - address changes, the local system MUST NOT use that address as the + On a point-to-point link, the source address of a BFD Control packet + MUST NOT be used to identify the session. This means that the + initial BFD packet MUST be accepted with any source address, and that + subsequent BFD packets MUST be demultiplexed solely by the Your + Discriminator field (as is always the case.) This allows the source + address to change if necessary. If the received source address + changes, the local system MUST NOT use that address as the destination in outgoing BFD Control packets; rather it MUST continue to use the address configured at session creation. An implementation MAY notify the application that the neighbor's source address has 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) + Limit 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 Tunnels 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 + TTL or Hop Limit 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-07.txt, January, 2008. [BFD-GENERIC] Katz, D., and Ward, D., "Generic Application of BFD", draft-ietf-bfd-generic-04.txt, January, 2008. [GTSM] Gill, V., et al, "The Generalized TTL Security Mechanism (GTSM)", RFC 5082, October, 2007. [KEYWORD] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. Security Considerations - In this application, the use of TTL=255 on transmit and receive is - viewed as supplying equivalent security characteristics to other - protocols used in the infrastructure, as it is not trivially - spoofable. The security implications of this mechanism are further - discussed in [GTSM]. + In this application, the use of TTL=255 on transmit and receive, + coupled with an association to an incoming interface, is viewed as + supplying equivalent security characteristics to other protocols used + in the infrastructure, as it is not trivially spoofable. The + security implications of this mechanism are further discussed in + [GTSM]. The security implications of the use of BFD Authentication are discussed in [BFD]. The use of the TTL=255 check simultaneously with BFD Authentication provides a low overhead mechanism for discarding a class of unauthorized packets and may be useful in implementations in which cryptographic checksum use is susceptable to denial of service attacks. The use or non-use of this mechanism does not impact interoperability. @@ -232,22 +233,22 @@ 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 - This is a reissue of the previous version. There are only minor - editorial changes. + Section 6 was changed to lump all point-to-point link types together. + Otherwise, only minor editorial changes were made. 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 @@ -280,11 +281,11 @@ 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. - This document expires in July, 2008. + This document expires in September, 2008.