--- 1/draft-ietf-6man-rfc6434-bis-05.txt 2018-03-04 06:16:01.234098902 -0800 +++ 2/draft-ietf-6man-rfc6434-bis-06.txt 2018-03-04 06:16:01.314100794 -0800 @@ -1,21 +1,21 @@ Internet Engineering Task Force T. Chown Internet-Draft Jisc Obsoletes: 6434 (if approved) J. Loughney Intended status: Best Current Practice Intel -Expires: August 31, 2018 T. Winters +Expires: September 4, 2018 T. Winters UNH-IOL - February 27, 2018 + March 3, 2018 IPv6 Node Requirements - draft-ietf-6man-rfc6434-bis-05 + draft-ietf-6man-rfc6434-bis-06 Abstract This document defines requirements for IPv6 nodes. It is expected that IPv6 will be deployed in a wide range of devices and situations. Specifying the requirements for IPv6 nodes allows IPv6 to function well and interoperate in a large number of situations and deployments. This document obsoletes RFC 6434, and in turn RFC 4294. @@ -28,21 +28,21 @@ 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 August 31, 2018. + This Internet-Draft will expire on September 4, 2018. Copyright Notice Copyright (c) 2018 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 @@ -59,85 +59,85 @@ 1.2. Description of IPv6 Nodes . . . . . . . . . . . . . . . . 5 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 3. Abbreviations Used in This Document . . . . . . . . . . . . . 5 4. Sub-IP Layer . . . . . . . . . . . . . . . . . . . . . . . . 5 5. IP Layer . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Internet Protocol Version 6 - RFC 8200 . . . . . . . . . 6 5.2. Support for IPv6 Extension Headers . . . . . . . . . . . 7 5.3. Protecting a node from excessive EH options . . . . . . . 8 5.4. Neighbor Discovery for IPv6 - RFC 4861 . . . . . . . . . 9 5.5. SEcure Neighbor Discovery (SEND) - RFC 3971 . . . . . . . 10 - 5.6. IPv6 Router Advertisement Flags Option - RFC 5175 . . . . 10 + 5.6. IPv6 Router Advertisement Flags Option - RFC 5175 . . . . 11 5.7. Path MTU Discovery and Packet Size . . . . . . . . . . . 11 5.7.1. Path MTU Discovery - RFC 8201 . . . . . . . . . . . . 11 - 5.7.2. Minimum MTU considerations . . . . . . . . . . . . . 11 + 5.7.2. Minimum MTU considerations . . . . . . . . . . . . . 12 5.8. ICMP for the Internet Protocol Version 6 (IPv6) - RFC - 4443 . . . . . . . . . . . . . . . . . . . . . . . . . . 11 + 4443 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.9. Default Router Preferences and More-Specific Routes - RFC - 4191 . . . . . . . . . . . . . . . . . . . . . . . . . . 11 + 4191 . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.10. First-Hop Router Selection - RFC 8028 . . . . . . . . . . 12 5.11. Multicast Listener Discovery (MLD) for IPv6 - RFC 3810 . 12 - 5.12. Explicit Congestion Notification (ECN) - RFC 3168 . . . . 12 - 6. Addressing and Address Configuration . . . . . . . . . . . . 12 - 6.1. IP Version 6 Addressing Architecture - RFC 4291 . . . . . 12 + 5.12. Explicit Congestion Notification (ECN) - RFC 3168 . . . . 13 + 6. Addressing and Address Configuration . . . . . . . . . . . . 13 + 6.1. IP Version 6 Addressing Architecture - RFC 4291 . . . . . 13 6.2. Host Address Availability Recommendations . . . . . . . . 13 - 6.3. IPv6 Stateless Address Autoconfiguration - RFC 4862 . . . 13 + 6.3. IPv6 Stateless Address Autoconfiguration - RFC 4862 . . . 14 6.4. Privacy Extensions for Address Configuration in IPv6 - - RFC 4941 . . . . . . . . . . . . . . . . . . . . . . . . 14 + RFC 4941 . . . . . . . . . . . . . . . . . . . . . . . . 15 6.5. Stateful Address Autoconfiguration (DHCPv6) - RFC 3315 . 15 - 6.6. Default Address Selection for IPv6 - RFC 6724 . . . . . . 15 - 7. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 + 6.6. Default Address Selection for IPv6 - RFC 6724 . . . . . . 16 + 7. DNS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 8. Configuring Non-Address Information . . . . . . . . . . . . . 16 8.1. DHCP for Other Configuration Information . . . . . . . . 16 - 8.2. Router Advertisements and Default Gateway . . . . . . . . 16 + 8.2. Router Advertisements and Default Gateway . . . . . . . . 17 8.3. IPv6 Router Advertisement Options for DNS - Configuration - RFC 8106 . . . . . . . . . . . . . . . . 16 + Configuration - RFC 8106 . . . . . . . . . . . . . . . . 17 8.4. DHCP Options versus Router Advertisement Options for Host Configuration . . . . . . . . . . . . . . . . . . . . . . 17 - 9. Service Discovery Protocols . . . . . . . . . . . . . . . . . 17 + 9. Service Discovery Protocols . . . . . . . . . . . . . . . . . 18 10. IPv4 Support and Transition . . . . . . . . . . . . . . . . . 18 10.1. Transition Mechanisms . . . . . . . . . . . . . . . . . 18 10.1.1. Basic Transition Mechanisms for IPv6 Hosts and Routers - RFC 4213 . . . . . . . . . . . . . . . . . 18 11. Application Support . . . . . . . . . . . . . . . . . . . . . 18 11.1. Textual Representation of IPv6 Addresses - RFC 5952 . . 18 11.2. Application Programming Interfaces (APIs) . . . . . . . 18 12. Mobility . . . . . . . . . . . . . . . . . . . . . . . . . . 19 - 13. Security . . . . . . . . . . . . . . . . . . . . . . . . . . 19 + 13. Security . . . . . . . . . . . . . . . . . . . . . . . . . . 20 13.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 21 13.2. Transforms and Algorithms . . . . . . . . . . . . . . . 21 - 14. Router-Specific Functionality . . . . . . . . . . . . . . . . 21 - 14.1. IPv6 Router Alert Option - RFC 2711 . . . . . . . . . . 21 + 14. Router-Specific Functionality . . . . . . . . . . . . . . . . 22 + 14.1. IPv6 Router Alert Option - RFC 2711 . . . . . . . . . . 22 14.2. Neighbor Discovery for IPv6 - RFC 4861 . . . . . . . . . 22 14.3. Stateful Address Autoconfiguration (DHCPv6) - RFC 3315 . 22 14.4. IPv6 Prefix Length Recommendation for Forwarding - BCP - 198 . . . . . . . . . . . . . . . . . . . . . . . . . . 22 - 15. Constrained Devices . . . . . . . . . . . . . . . . . . . . . 22 + 198 . . . . . . . . . . . . . . . . . . . . . . . . . . 23 + 15. Constrained Devices . . . . . . . . . . . . . . . . . . . . . 23 16. Network Management . . . . . . . . . . . . . . . . . . . . . 23 - 16.1. Management Information Base (MIB) Modules . . . . . . . 23 - 16.1.1. IP Forwarding Table MIB . . . . . . . . . . . . . . 23 + 16.1. Management Information Base (MIB) Modules . . . . . . . 24 + 16.1.1. IP Forwarding Table MIB . . . . . . . . . . . . . . 24 16.1.2. Management Information Base for the Internet - Protocol (IP) . . . . . . . . . . . . . . . . . . . 23 - 16.1.3. Interface MIB . . . . . . . . . . . . . . . . . . . 23 + Protocol (IP) . . . . . . . . . . . . . . . . . . . 24 + 16.1.3. Interface MIB . . . . . . . . . . . . . . . . . . . 24 16.2. YANG Data Models . . . . . . . . . . . . . . . . . . . . 24 16.2.1. IP Management YANG Model . . . . . . . . . . . . . . 24 16.2.2. Interface Management YANG Model . . . . . . . . . . 24 17. Security Considerations . . . . . . . . . . . . . . . . . . . 24 - 18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 - 19. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 24 - 19.1. Authors and Acknowledgments (Current Document) . . . . . 24 - 19.2. Authors and Acknowledgments from RFC 6434 . . . . . . . 24 + 18. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 + 19. Authors and Acknowledgments . . . . . . . . . . . . . . . . . 25 + 19.1. Authors and Acknowledgments (Current Document) . . . . . 25 + 19.2. Authors and Acknowledgments from RFC 6434 . . . . . . . 25 19.3. Authors and Acknowledgments from RFC 4294 . . . . . . . 25 - 20. Appendix: Changes from RFC 6434 . . . . . . . . . . . . . . . 26 + 20. Appendix: Changes from RFC 6434 . . . . . . . . . . . . . . . 25 21. Appendix: Changes from RFC 4294 . . . . . . . . . . . . . . . 27 - 22. References . . . . . . . . . . . . . . . . . . . . . . . . . 29 - 22.1. Normative References . . . . . . . . . . . . . . . . . . 29 + 22. References . . . . . . . . . . . . . . . . . . . . . . . . . 28 + 22.1. Normative References . . . . . . . . . . . . . . . . . . 28 22.2. Informative References . . . . . . . . . . . . . . . . . 35 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 40 1. Introduction This document defines common functionality required by both IPv6 hosts and routers. Many IPv6 nodes will implement optional or additional features, but this document collects and summarizes requirements from other published Standards Track documents in one place. @@ -266,80 +266,105 @@ 5.1. Internet Protocol Version 6 - RFC 8200 The Internet Protocol Version 6 is specified in [RFC8200]. This specification MUST be supported. The node MUST follow the packet transmission rules in RFC 8200. All conformant IPv6 implementations MUST be capable of sending and receiving IPv6 packets; forwarding functionality MAY be supported. Nodes MUST always be able to send, receive, and process fragment - headers. Overlapping fragments MUST be handled as described in - [RFC5722]. + headers. + + IPv6 nodes must not create overlapping fragments. Also, when + reassembling an IPv6 datagram, if one or more of its constituent + fragments is determined to be an overlapping fragment, the entire + datagram (and any constituent fragments) must be silently discarded. + See [RFC5722] for more information. + + As recommended in [RFC8021], nodes MUST NOT generate atomic + fragments, i.e., where the fragment is a whole datagram. As per + + [RFC6946], if a receiving node reassembling a datagram encounters an + atomic fragment, it should be processed as a fully reassembled + packet, and any other fragments that match this packet should be + processed independently. [RFC6946] discusses IPv6 atomic fragments, and recommends that IPv6 atomic fragments are processed independently of any other fragments, - to protect against fragmentation-based attacks. [RFC8021] goes - further and recommends the deprecation of atomic fragments. Nodes - thus MUST NOT generate atomic fragments. + to protect against fragmentation-based attacks. To mitigate a variety of potential attacks, nodes SHOULD avoid using predictable fragment Identification values in Fragment Headers, as discussed in [RFC7739]. All nodes SHOULD support the setting and use of the IPv6 Flow Label field as defined in the IPv6 Flow Label specification [RFC6437]. Forwarding nodes such as routers and load distributors MUST NOT depend only on Flow Label values being uniformly distributed. It is RECOMMENDED that source hosts support the flow label by setting the Flow Label field for all packets of a given flow to the same value chosen from an approximation to a discrete uniform distribution. 5.2. Support for IPv6 Extension Headers RFC 8200 specifies extension headers and the processing for these headers. + Extension headers (except for the Hop-by-Hop Options header) are not + processed, inserted, or deleted by any node along a packet's delivery + path, until the packet reaches the node (or each of the set of nodes, + in the case of multicast) identified in the Destination Address field + of the IPv6 header. + Any unrecognized extension headers or options MUST be processed as described in RFC 8200. Note that where Section 4 of RFC 8200 refers to the action to be taken when a Next Header value in the current header is not recognized by a node, that action applies whether the value is an unrecognized Extension Header or an unrecognized upper layer protocol (ULP). An IPv6 node MUST be able to process these headers. An exception is Routing Header type 0 (RH0), which was deprecated by [RFC5095] due to security concerns and which MUST be treated as an unrecognized routing type. Further, [RFC7045] adds specific requirements for processing of Extension Headers, in particular that any forwarding node along an IPv6 packet's path, which forwards the packet for any reason, SHOULD do so regardless of any extension headers that are present. - [RFC7112] discusses issues with oversized IPv6 Extension Header - chains, and states that when a node fragments an IPv6 datagram, it - MUST include the entire IPv6 Header Chain in the First Fragment. - - As stated in RFC8200, extension headers (except for the Hop-by-Hop - Options header) are not processed, inserted, or deleted by any node - along a packet's delivery path, until the packet reaches the node (or - each of the set of nodes, in the case of multicast) identified in the - Destination Address field of the IPv6 header. + As per RFC 8200, when a node fragments an IPv6 datagram, it MUST + include the entire IPv6 Header Chain in the first fragment. The Per- + Fragment headers must consist of the IPv6 header plus any extension + headers that must be processed by nodes en route to the destination, + that is, all headers up to and including the Routing header if + present, else the Hop-by-Hop Options header if present, else no + extension headers. On reassembly, if the first fragment does not + include all headers through an Upper-Layer header, then that fragment + should be discarded and an ICMP Parameter Problem, Code 3, message + should be sent to the source of the fragment, with the Pointer field + set to zero. See [RFC7112] for a discussion of why oversized IPv6 + Extension Header chains are avoided. - It should be noted that when future, new Extension Headers are - defined, the consistent format described in Section 4 of [RFC6564] - MUST be followed. + Defining new IPv6 extension headers is not recommended, unless there + are no existing IPv6 extension headers that can be used by specifying + a new option for that IPv6 extension header. A proposal to specify a + new IPv6 extension header must include a detailed technical + explanation of why an existing IPv6 extension header can not be used + for the desired new function, and in such cases need to follow the + format described in Section 8 of RFC 8200. For further background + reading on this topic, see [RFC6564]. 5.3. Protecting a node from excessive EH options - Per RFC 8200, end hosts are expected to process all extension + As per RFC 8200, end hosts are expected to process all extension headers, destination options, and hop-by-hop options in a packet. Given that the only limit on the number and size of extension headers is the MTU, the processing of received packets could be considerable. It is also conceivable that a long chain of extension headers might be used as a form of denial-of-service attack. Accordingly, a host may place limits on the number and sizes of extension headers and options it is willing to process. A host MAY limit the number of consecutive PAD1 options in destination options or hop-by-hop options to seven. In this case, if @@ -442,27 +467,27 @@ 5.5. SEcure Neighbor Discovery (SEND) - RFC 3971 SEND [RFC3971] and Cryptographically Generated Addresses (CGAs) [RFC3972] provide a way to secure the message exchanges of Neighbor Discovery. SEND has the potential to address certain classes of spoofing attacks, but it does not provide specific protection for threats from off-link attackers. There have been relatively few implementations of SEND in common - operating systems and platforms, and thus deployment experience has - been limited to date. + operating systems and platforms since its publication in 2005, and + thus deployment experience remains very limited to date. - At this time, SEND is considered optional. Due to the complexity in - deploying SEND, and its heavyweight provisioning, its deployment is - only likely to be considered where nodes are operating in a - particularly strict security environment. + At this time, support for SEND is considered optional. Due to the + complexity in deploying SEND, and its heavyweight provisioning, its + deployment is only likely to be considered where nodes are operating + in a particularly strict security environment. 5.6. IPv6 Router Advertisement Flags Option - RFC 5175 Router Advertisements include an 8-bit field of single-bit Router Advertisement flags. The Router Advertisement Flags Option extends the number of available flag bits by 48 bits. At the time of this writing, 6 of the original 8 single-bit flags have been assigned, while 2 remain available for future assignment. No flags have been defined that make use of the new option, and thus, strictly speaking, there is no requirement to implement the option today. However, @@ -481,26 +506,34 @@ It is strongly recommended that IPv6 nodes implement Path MTU Discovery [RFC8201], in order to discover and take advantage of path MTUs greater than 1280 octets. However, a minimal IPv6 implementation (e.g., in a boot ROM) may simply restrict itself to sending packets no larger than 1280 octets, and omit implementation of Path MTU Discovery. The rules in [RFC8200] and [RFC5722] MUST be followed for packet fragmentation and reassembly. - One operational issue with Path MTU Discovery occurs when, contrary - to the guidance in [RFC4890], firewalls block ICMP Packet Too Big - messages. Path MTU Discovery relies on such messages to determine - what size messages can be successfully sent. "Packetization Layer - Path MTU Discovery" [RFC4821] avoids having a dependency on Packet - Too Big messages. + As described in RFC 8201, nodes implementing Path MTU Discovery and + sending packets larger than the IPv6 minimum link MTU are susceptible + to problematic connectivity if ICMPv6 messages are blocked or not + transmitted. For example, this will result in connections that + complete the TCP three- way handshake correctly but then hang when + data is transferred. This state is referred to as a black-hole + connection [RFC2923]. Path MTU Discovery relies on ICMPv6 Packet Too + Big (PTB) to determine the MTU of the path (and thus these should not + be filtered, as per the recommendation in [RFC4890]). + + An extension to Path MTU Discovery defined in RFC 8201 can be found + in [RFC4821], which defines a method for Packetization Layer Path MTU + Discovery (PLPMTUD) designed for use over paths where delivery of + ICMPv6 messages to a host is not assured. 5.7.2. Minimum MTU considerations While an IPv6 link MTU can be set to 1280 bytes, it is recommended that for IPv6 UDP in particular, which includes DNS operation, the sender use a large MTU if they can, in order to avoid gratuitous fragmentation-caused packet drops. 5.8. ICMP for the Internet Protocol Version 6 (IPv6) - RFC 4443 @@ -1026,25 +1060,27 @@ routers. 14.4. IPv6 Prefix Length Recommendation for Forwarding - BCP 198 Forwarding nodes MUST conform to BCP 198 [RFC7608] and thus IPv6 implementations of nodes that may forward packets MUST conform to the rules specified in Section 5.1 of [RFC4632]. 15. Constrained Devices - The target for this document is general IPv6 nodes. In the case of - constrained nodes, with limited CPU, memory, bandwidth or power, - support for certain IPv6 functionality may need to be considered due - to those limitations. The requirements of this document are - RECOMMENDED for all nodes, including constrained nodes, but + The target for this document is general IPv6 nodes. In this Section, + we briefly discuss considerations for constrained devices. + + In the case of constrained nodes, with limited CPU, memory, bandwidth + or power, support for certain IPv6 functionality may need to be + considered due to those limitations. While the requirements of this + document are RECOMMENDED for all nodes, including constrained nodes, compromises may need to be made in certain cases. Where such compromises are made, the interoperability of devices should be strongly considered, paticularly where this may impact other nodes on the same link, e.g., only supporting MLDv1 will affect other nodes. The IETF 6LowPAN (IPv6 over Low Power LWPAN) WG defined six RFCs, including a general overview and problem statement ([RFC4919], the means by which IPv6 packets are transmitted over IEEE 802.15.4 networks [RFC4944] and ND optimisations for that medium [RFC6775]. @@ -1126,59 +1162,25 @@ iteration of this document, RFC6434. For this version of the document, the authors thanked Hitoshi Asaeda, Brian Carpenter, Tim Chown, Ralph Droms, Sheila Frankel, Sam Hartman, Bob Hinden, Paul Hoffman, Pekka Savola, Yaron Sheffer, and Dave Thaler. 19.3. Authors and Acknowledgments from RFC 4294 The original version of this document (RFC 4294) was written by the - IPv6 Node Requirements design team: - - Jari Arkko - jari.arkko@ericsson.com - - Marc Blanchet - marc.blanchet@viagenie.qc.ca - - Samita Chakrabarti - samita.chakrabarti@eng.sun.com - - Alain Durand - alain.durand@sun.com - - Gerard Gastaud - gerard.gastaud@alcatel.fr - - Jun-ichiro Itojun Hagino - itojun@iijlab.net - - Atsushi Inoue - inoue@isl.rdc.toshiba.co.jp - - Masahiro Ishiyama - masahiro@isl.rdc.toshiba.co.jp - - John Loughney - john.loughney@nokia.com - - Rajiv Raghunarayan - raraghun@cisco.com - Shoichi Sakane - shouichi.sakane@jp.yokogawa.com - - Dave Thaler - dthaler@windows.microsoft.com - - Juha Wiljakka - juha.wiljakka@Nokia.com + IPv6 Node Requirements design team, which had the following members: + Jari Arkko, Marc Blanchet, Samita Chakrabarti, Alain Durand, Gerard + Gastaud, Jun-ichiro Itojun Hagino, Atsushi Inoue, Masahiro Ishiyama, + John Loughney, Rajiv Raghunarayan, Shoichi Sakane, Dave Thaler, and + Juha Wiljakka. The authors would like to thank Ran Atkinson, Jim Bound, Brian Carpenter, Ralph Droms, Christian Huitema, Adam Machalek, Thomas Narten, Juha Ollila, and Pekka Savola for their comments. Thanks to Mark Andrews for comments and corrections on DNS text. Thanks to Alfred Hoenes for tracking the updates to various RFCs. 20. Appendix: Changes from RFC 6434 There have been many editorial clarifications as well as significant @@ -1246,20 +1248,23 @@ 26. Added reference to RFC8064 for stable address creation. 27. Added text on protection from excessive EH options 28. Added text on dangers of 1280 MTU UDP, esp. wrt DNS traffic 29. Added text to clarify RFC8200 behaviour for unrecognized EHs or unrecognized ULPs + 30. Removed dated email addresses from design team acknowledgements + for RFC 4294. + 21. Appendix: Changes from RFC 4294 There have been many editorial clarifications as well as significant additions and updates. While this section highlights some of the changes, readers should not rely on this section for a comprehensive list of all changes. 1. Updated the Introduction to indicate that this document is an applicability statement and is aimed at general nodes. @@ -1659,20 +1664,24 @@ [RFC2491] Armitage, G., Schulter, P., Jork, M., and G. Harter, "IPv6 over Non-Broadcast Multiple Access (NBMA) networks", RFC 2491, DOI 10.17487/RFC2491, January 1999, . [RFC2590] Conta, A., Malis, A., and M. Mueller, "Transmission of IPv6 Packets over Frame Relay Networks Specification", RFC 2590, DOI 10.17487/RFC2590, May 1999, . + [RFC2923] Lahey, K., "TCP Problems with Path MTU Discovery", + RFC 2923, DOI 10.17487/RFC2923, September 2000, + . + [RFC3146] Fujisawa, K. and A. Onoe, "Transmission of IPv6 Packets over IEEE 1394 Networks", RFC 3146, DOI 10.17487/RFC3146, October 2001, . [RFC3363] Bush, R., Durand, A., Fink, B., Gudmundsson, O., and T. Hain, "Representing Internet Protocol version 6 (IPv6) Addresses in the Domain Name System (DNS)", RFC 3363, DOI 10.17487/RFC3363, August 2002, .