--- 1/draft-ietf-bfd-unsolicited-03.txt 2021-10-18 13:13:09.143724611 -0700 +++ 2/draft-ietf-bfd-unsolicited-04.txt 2021-10-18 13:13:09.171725309 -0700 @@ -1,22 +1,22 @@ Network Working Group E. Chen Internet-Draft Palo Alto Networks Intended status: Standards Track N. Shen -Expires: October 24, 2021 Zededa +Expires: April 18, 2022 Zededa R. Raszuk NTT Network Innovations R. Rahman - April 22, 2021 + October 15, 2021 Unsolicited BFD for Sessionless Applications - draft-ietf-bfd-unsolicited-03 + draft-ietf-bfd-unsolicited-04 Abstract For operational simplification of "sessionless" applications using BFD, in this document we present procedures for "unsolicited BFD" that allow a BFD session to be initiated by only one side, and be established without explicit per-session configuration or registration by the other side (subject to certain per-interface or per-router policies). @@ -36,52 +36,53 @@ 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 https://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 October 24, 2021. + This Internet-Draft will expire on April 18, 2022. Copyright Notice Copyright (c) 2021 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 (https://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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Procedures for Unsolicited BFD . . . . . . . . . . . . . . . 3 - 3. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 4 - 3.1. Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . . 4 - 3.2. Unsolicited BFD Module . . . . . . . . . . . . . . . . . 5 - 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 - 5. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 - 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 - 6.1. BFD Protocol Security Considerations . . . . . . . . . . 9 - 6.2. YANG Module Security Considerations . . . . . . . . . . . 9 - 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 - 7.1. Normative References . . . . . . . . . . . . . . . . . . 10 - 7.2. Informative References . . . . . . . . . . . . . . . . . 12 + 3. State Variables . . . . . . . . . . . . . . . . . . . . . . . 4 + 4. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 5 + 4.1. Unsolicited BFD Hierarchy . . . . . . . . . . . . . . . . 5 + 4.2. Unsolicited BFD Module . . . . . . . . . . . . . . . . . 5 + 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 + 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 + 7.1. BFD Protocol Security Considerations . . . . . . . . . . 9 + 7.2. YANG Module Security Considerations . . . . . . . . . . . 9 + 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 + 8.1. Normative References . . . . . . . . . . . . . . . . . . 11 + 8.2. Informative References . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 1. Introduction The current implementation and deployment practice for BFD ([RFC5880] and [RFC5881]) usually requires BFD sessions be explicitly configured or registered on both sides. This requirement is not an issue when an application like BGP [RFC4271] has the concept of a "session" that involves both sides for its establishment. However, this requirement can be operationally challenging when the prerequisite "session" does @@ -130,57 +131,75 @@ Server, multiple BGP paths (when exist) can be made available to the clients of the Router Server as described in [RFC7947]. The "unsolicited BFD" can be used in BGP route selection by these clients to eliminate paths with "inaccessible nexthops". 2. Procedures for Unsolicited BFD With "unsolicited BFD", one side takes the "Active role" and the other side takes only the "Passive role" as described in [RFC5880]. - On the passive side, the "unsolicited BFD" SHOULD be explicitely + On the passive side, the "unsolicited BFD" SHOULD be explicitly configured on an interface or globally (apply to all interfaces). The BFD parameters can be either per-interface or per-router based. It MAY also choose to use the parameters that the active side uses in its BFD Control packets. The "My Discriminator", however, MUST be chosen to allow multiple unsolicited BFD sessions. The active side starts sending the BFD Control packets as specified in [RFC5880]. The passive side does not send BFD Control packets. When the passive side receives a BFD Control packet from the active side with 0 as "Your Discriminator", and it does not find an existing session with the same source address and the same "Discriminator" pairs as in the packet and "unsolicited BFD" is allowed on the - interface by local policy, it SHOULD then create a matching BFD - session toward the active side (based on the source address and - destination address in the BFD Control packet) as if the session were - locally registered. It would then start sending the BFD Control - packets and perform necessary procedure for bringing up, maintaining - and tearing down the BFD session. If the BFD session fails to get - established within certain specified time, or if an established BFD - session goes down, the passive side would stop sending BFD Control - packets and delete the BFD session created until the BFD Control - packets is initiated by the active side again. + interface by local policy, it MUST create a matching BFD session + toward the active side (based on the source address and destination + address in the BFD Control packet) as if the session were locally + registered. It would then start sending the BFD Control packets and + perform necessary procedure for bringing up, maintaining and tearing + down the BFD session. If the BFD session fails to get established + within certain specified time, or if an established BFD session goes + down, the passive side would stop sending BFD Control packets and MAY + delete the BFD session created until the BFD Control packets is + initiated by the active side again. + + When on the passive side Unsolicited BFD sessions goes down an + implementation MAY keep such session state for a configurable amount + of time. Temporarily keeping such local state may permit retrieving + additional operational information of such session which went down. The "Passive role" may change to the "Active role" when a local client registers for the same BFD session, and from the "Active role " to the "Passive role " when there is no longer any locally registered client for the BFD session. -3. YANG Data Model +3. State Variables + + This document defines a new state variable called Unsolicited Role. + + bfd.UnsolicitedRole + + The operational mode of BFD interface when configured for unsolicited + behaviour. Options can be either PASSIVE, ACTIVE or NULL (NULL - not + initialized) for unsolicited BFD sessions. Default (not configured + for unsolicited behaviour) MUST be set to NULL if present on the + interface. + +4. YANG Data Model This section extends the YANG data model for BFD [I-D.ietf-bfd-yang] to cover the unsolicited BFD. -3.1. Unsolicited BFD Hierarchy +4.1. Unsolicited BFD Hierarchy + module: ietf-bfd-unsolicited augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh: +--rw unsolicited {bfd-unsol:unsolicited-params-global}? +--rw enable? boolean +--rw local-multiplier? multiplier +--rw (interval-config-type)? +--:(tx-rx-intervals) | +--rw desired-min-tx-interval? uint32 | +--rw required-min-rx-interval? uint32 @@ -197,48 +216,47 @@ | +--rw desired-min-tx-interval? uint32 | +--rw required-min-rx-interval? uint32 +--:(single-interval) {single-minimum-interval}? +--rw min-interval? uint32 augment /rt:routing/rt:control-plane-protocols /rt:control-plane-protocol/bfd:bfd/bfd-ip-sh:ip-sh /bfd-ip-sh:sessions/bfd-ip-sh:session: +--ro unsolicited +--ro role? bfd-unsol:unsolicited-role -3.2. Unsolicited BFD Module +4.2. Unsolicited BFD Module - file "ietf-bfd-unsolicited@2019-06-26.yang" + file "ietf-bfd-unsolicited@2021-10-15.yang" module ietf-bfd-unsolicited { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-bfd-unsolicited"; - prefix "bfd-unsol"; - // RFC Ed.: replace occurences of XXXX/YYYY with actual RFC numbers + // RFC Ed.: replace occurences of YYYY with actual RFC numbers // and remove this note import ietf-bfd-types { prefix "bfd-types"; - reference "RFC XXXX: YANG Data Model for BFD"; + reference "RFC 9127: YANG Data Model for BFD"; } import ietf-bfd { prefix "bfd"; - reference "RFC XXXX: YANG Data Model for BFD"; + reference "RFC 9127: YANG Data Model for BFD"; } import ietf-bfd-ip-sh { prefix "bfd-ip-sh"; - reference "RFC XXXX: YANG Data Model for BFD"; + reference "RFC 9127: YANG Data Model for BFD"; } import ietf-routing { prefix "rt"; reference "RFC 8349: A YANG Data Model for Routing Management (NMDA version)"; } organization "IETF BFD Working Group"; @@ -249,38 +267,38 @@ Editors: Enke Chen (enchen@paloaltonetworks.com), Naiming Shen (naiming@zededa.com), Robert Raszuk (robert@raszuk.net), Reshad Rahman (reshad@yahoo.com)"; description "This module contains the YANG definition for BFD unsolicited as per RFC YYYY. - Copyright (c) 2018 IETF Trust and the persons + Copyright (c) 2021 IETF Trust and the persons identified as authors of the code. All rights reserved. Redistribution and use in source and binary forms, with or without modification, is permitted pursuant to, and subject to the license terms contained in, the Simplified BSD License set forth in Section 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info). - This version of this YANG module is part of RFC XXXX; see + This version of this YANG module is part of RFC YYYY; see the RFC itself for full legal notices."; reference "RFC YYYY"; - revision 2019-06-26 { + revision 2021-10-15 { description "Initial revision."; - reference "RFC YYYY: A YANG data model for BFD unsolicited"; + reference "RFC 9127: A YANG data model for BFD unsolicited"; } /* * Feature definitions */ feature unsolicited-params-global { description "This feature indicates that the server supports global parameters for unsolicited sessions."; } @@ -352,60 +369,61 @@ description "Augmentation for BFD unsolicited on IP single-hop session"; container unsolicited { config false; description "BFD IP single-hop session unsolicited top level container"; leaf role { type bfd-unsol:unsolicited-role; description "Role."; } + } } } -4. IANA Considerations +5. IANA Considerations This documents makes no IANA requests. -5. Acknowledgments +6. Acknowledgments Authors would like to thank Acee Lindem, Greg Mirsky and Raj Chetan for their review and valuable input. -6. Security Considerations +7. Security Considerations -6.1. BFD Protocol Security Considerations +7.1. BFD Protocol Security Considerations - The same security considerations as those described in [RFC5880] and - [RFC5881] apply to this document. With "unsolicited BFD" there is - potential risk for excessive resource usage by BFD from "unexpected" - remote systems. To mitigate such risks, the following measures are - RECOMMENDED: + The same security considerations and protection measures as those + described in [RFC5880] and [RFC5881] normatively apply to this + document. With "unsolicited BFD" there is potential risk for + excessive resource usage by BFD from "unexpected" remote systems. To + mitigate such risks, the following measures are mandatory: o Limit the feature to specific interfaces, and to a single-hop BFD with "TTL=255" [RFC5082]. For numbered interfaces source address of an incoming BFD packet should belongs to the subnet of the interface from which the BFD packet is received. For unnumbered - interfaces the above check should be alinged with routing protocol + interfaces the above check should be aligned with routing protocol addresses running on such pair of interfaces. o Apply "access control" to allow BFD packets only from certain subnets or hosts. o Deploy the feature only in certain "trustworthy" environment, e.g., at an IXP, or between a provider and its customers. o Adjust BFD parameters as needed for the particular deployment and scale. o Use BFD authentication. -6.2. YANG Module Security Considerations +7.2. YANG Module Security Considerations The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC5246]. The NETCONF access control model [RFC6536] provides the means to @@ -418,48 +436,47 @@ default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability: /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh /unsolicited: o data node "enable" enables creation of unsolicited BFD IP single- - hop sessions globally, i.e. on all interfaces. See Section 6.1. + hop sessions globally, i.e. on all interfaces. See Section 7.1. o data nodes local-multiplier, desired-min-tx-interval, required- min-rx-interval and min-interval all impact the parameters of the unsolicited BFD IP single-hop sessions. /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh /interfaces/interface/unsolicited: o data node "enable" enables creation of unsolicited BFD IP single- - hop sessions on a specific interface. See Section 6.1. + hop sessions on a specific interface. See Section 7.1. o data nodes local-multiplier, desired-min-tx-interval, required- min-rx-interval and min-interval all impact the parameters of the unsolicited BFD IP single-hop sessions on the interface. Some of the readable data nodes in this YANG module may be considered sensitive or vulnerable in some network environments. It is thus important to control read access (e.g., via get, get-config, or notification) to these data nodes. These are the subtrees and data nodes and their sensitivity/vulnerability: /routing/control-plane-protocols/control-plane-protocol/bfd/ip-sh /sessions/session/unsolicited: access to this information discloses the role of the local system in the creation of the unsolicited BFD session. -7. References - -7.1. Normative References +8. References +8.1. Normative References [I-D.ietf-bfd-yang] Rahman, R., Zheng, L., Jethanandani, M., Pallagatti, S., and G. Mirsky, "YANG Data Model for Bidirectional Forwarding Detection (BFD)", draft-ietf-bfd-yang-17 (work in progress), August 2018. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, @@ -499,24 +516,24 @@ . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . -7.2. Informative References +8.2. Informative References [I-D.ietf-idr-rs-bfd] - Bush, R., Haas, J., Scudder, J., Nipper, A., and C. + Bush, R., Haas, J., Scudder, J. G., Nipper, A., and C. Dietzel, "Making Route Servers Aware of Data Link Failures at IXPs", draft-ietf-idr-rs-bfd-09 (work in progress), September 2020. [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, January 2006, . [RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.