IPv6 Node Requirements RFC 4294-bis

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.

The goal of this document is to define the common functionality required from both IPv6 hosts and routers. Many IPv6 nodes will implement optional or additional features, but this document summarizes requirements from other published Standards Track documents in one place. This document tries to avoid discussion of protocol details, and references RFCs for this purpose. This document is informational in nature and does not update Standards Track RFCs. Although the document points to different specifications, it should be noted that in most cases, the granularity of requirements are smaller than a single specification, as many specifications define multiple, independent pieces, some of which may not be mandatory. As it is not always possible for an implementer to know the exact usage of IPv6 in a node, an overriding requirement for IPv6 nodes is that they should adhere to Jon Postel's Robustness Principle: Be conservative in what you do, be liberal in what you accept from others .

IPv6 covers many specifications. It is intended that IPv6 will be deployed in many different situations and environments. Therefore, it is important to develop the requirements for IPv6 nodes to ensure interoperability. This document assumes that all IPv6 nodes meet the minimum requirements specified here.

From the Internet Protocol, Version 6 (IPv6) Specification , we have the following definitions: Description of an IPv6 Node - a device that implements IPv6. Description of an IPv6 router - a node that forwards IPv6 packets not explicitly addressed to itself. Description of an IPv6 Host - any node that is not a router.

ATM Asynchronous Transfer Mode AH Authentication Header DAD Duplicate Address Detection ESP Encapsulating Security Payload ICMP Internet Control Message Protocol IKE Internet Key Exchange MIB Management Information Base MLD Multicast Listener Discovery MTU Maximum Transfer Unit NA Neighbor Advertisement NBMA Non-Broadcast Multiple Access ND Neighbor Discovery NS Neighbor Solicitation NUD Neighbor Unreachability Detection PPP Point-to-Point Protocol PVC Permanent Virtual Circuit SVC Switched Virtual Circuit

An IPv6 node must include support for one or more IPv6 link-layer specifications. Which link-layer specifications are included will depend upon what link-layers are supported by the hardware available on the system. It is possible for a conformant IPv6 node to support IPv6 on some of its interfaces and not on others. As IPv6 is run over new layer 2 technologies, it is expected that new specifications will be issued. This section highlights some major layer 2 technologies and is not intended to be complete.

Nodes supporting IPv6 over Ethernet interfaces MUST implement Transmission of IPv6 Packets over Ethernet Networks .

Nodes supporting IPv6 over PPP MUST implement IPv6 over PPP .

Nodes supporting IPv6 over ATM Networks MUST implement IPv6 over ATM Networks . Additionally, RFC 2492 states: A minimally conforming IPv6/ATM driver SHALL support the PVC mode of operation. An IPv6/ATM driver that supports the full SVC mode SHALL also support PVC mode of operation.

The Internet Protocol Version 6 is specified in . This specification MUST be supported. Unrecognized options in Hop-by-Hop Options or Destination Options extensions MUST be processed as described in RFC 2460. The node MUST follow the packet transmission rules in RFC 2460. Nodes MUST always be able to send, receive, and process fragment headers. All conformant IPv6 implementations MUST be capable of sending and receiving IPv6 packets; the forwarding functionality MAY be supported. RFC 2460 specifies extension headers and the processing for these headers. A full implementation of IPv6 includes implementation of the following extension headers: Hop-by-Hop Options, Routing (Type 0), Fragment, Destination Options, Authentication and Encapsulating Security Payload . An IPv6 node MUST be able to process these headers. It should be noted that there is some discussion about the use of Routing Headers and possible security threats 'IPv6-RH' that they cause.

Neighbor Discovery SHOULD be supported. states: Unless specified otherwise (in a document that covers operating IP over a particular link type) this document applies to all link types. However, because ND uses link-layer multicast for some of its services, it is possible that on some link types (e.g., NBMA links) alternative protocols or mechanisms to implement those services will be specified (in the appropriate document covering the operation of IP over a particular link type). The services described in this document that are not directly dependent on multicast, such as Redirects, Next-hop determination, Neighbor Unreachability Detection, etc., are expected to be provided as specified in this document. The details of how one uses ND on NBMA links is an area for further study. Some detailed analysis of Neighbor Discovery follows: Router Discovery is how hosts locate routers that reside on an attached link. Router Discovery MUST be supported for implementations. Prefix Discovery is how hosts discover the set of address prefixes that define which destinations are on-link for an attached link. Prefix discovery MUST be supported for implementations. Neighbor Unreachability Detection (NUD) MUST be supported for all paths between hosts and neighboring nodes. It is not required for paths between routers. However, when a node receives a unicast Neighbor Solicitation (NS) message (that may be a NUD's NS), the node MUST respond to it (i.e., send a unicast Neighbor Advertisement). Duplicate Address Detection MUST be supported on all links supporting link-layer multicast (RFC 4862, Section 5.4, specifies DAD MUST take place on all unicast addresses). A host implementation MUST support sending Router Solicitations. Receiving and processing Router Advertisements MUST be supported for host implementations. The ability to understand specific Router Advertisement options is dependent on supporting the specification where the RA is specified. Sending and Receiving Neighbor Solicitation (NS) and Neighbor Advertisement (NA) MUST be supported. NS and NA messages are required for Duplicate Address Detection (DAD). Redirect functionality SHOULD be supported. If the node is a router, Redirect functionality MUST be supported.

Path MTU Discovery SHOULD be supported, though minimal implementations MAY choose to not support it and avoid large packets. The rules in RFC 2460 MUST be followed for packet fragmentation and reassembly.

IPv6 Jumbograms MAY be supported.

ICMPv6 MUST be supported.

The IPv6 Addressing Architecture MUST be supported.

IPv6 Stateless Address Autoconfiguration is defined in . This specification MUST be supported for nodes that are hosts. Static address can be supported as well. Nodes that are routers MUST be able to generate link local addresses as described in RFC 4862 . From 4862: The autoconfiguration process specified in this document applies only to hosts and not routers. Since host autoconfiguration uses information advertised by routers, routers will need to be configured by some other means. However, it is expected that routers will generate link-local addresses using the mechanism described in this document. In addition, routers are expected to successfully pass the Duplicate Address Detection procedure described in this document on all addresses prior to assigning them to an interface. Duplicate Address Detection (DAD) MUST be supported.

Privacy Extensions for Stateless Address Autoconfiguration SHOULD be supported. It is recommended that this behavior be configurable on a connection basis within each application when available. It is noted that a number of applications do not work with addresses generated with this method, while other applications work quite well with them.

The rules specified in the Default Address Selection for IPv6 document MUST be implemented. It is expected that IPv6 nodes will need to deal with multiple addresses.

Stateful Address Autoconfiguration MAY be supported. DHCPv6 is the standard stateful address configuration protocol; see Section 5.3 for DHCPv6 support. Nodes which do not support Stateful Address Autoconfiguration may be unable to obtain any IPv6 addresses, aside from link-local addresses, when it receives a router advertisement with the 'M' flag (Managed address configuration) set and that contains no prefixes advertised for Stateless Address Autoconfiguration (see Section 4.5.2). Additionally, such nodes will be unable to obtain other configuration information, such as the addresses of DNS servers when it is connected to a link over which the node receives a router advertisement in which the 'O' flag (Other stateful configuration) is set.

Nodes that need to join multicast groups MUST support MLDv1 . MLDv1 is needed by any node that is expected to receive and process multicast traffic. Note that Neighbor Discovery (as used on most link types -- see Section 5.2) depends on multicast and requires that nodes join Solicited Node multicast addresses. Nodes that need to join multicast groups SHOULD implement MLDv2 . However, if the node has applications that only need support for Any-Source Multicast , the node MAY implement MLDv1 instead. If the node has applications that need support for Source-Specific Multicast , , the node MUST support MLDv2 . In all cases, nodes are strongly encouraged to implement MLDv2 rather than MLDv1, as the presence of a single MLDv1 participant on a link requires that all other nodes on the link operate in version 1 compatability mode. When MLDv1 is used, the rules in the Source Address Selection for the Multicast Listener Discovery (MLD) Protocol MUST be followed.

DNS is described in , , , and . Not all nodes will need to resolve names; those that will never need to resolve DNS names do not need to implement resolver functionality. However, the ability to resolve names is a basic infrastructure capability that applications rely on and generally needs to be supported. All nodes that need to resolve names SHOULD implement stub-resolver functionality, as in RFC 1034, Section 5.3.1, with support for: - AAAA type Resource Records ; - reverse addressing in ip6.arpa using PTR records ; - EDNS0 to allow for DNS packet sizes larger than 512 octets. Those nodes are RECOMMENDED to support DNS security extensions , , and . Those nodes are NOT RECOMMENDED to support the experimental A6 Resource Records .

The method by which IPv6 nodes that use DHCP for address assignment can obtain IPv6 addresses and other configuration information upon receipt of a Router Advertisement with the \'M' flag set is described in Section 5.5.3 of RFC 4862. In addition, in the absence of a router, those IPv6 nodes that use DHCP for address assignment MAY initiate DHCP to obtain IPv6 addresses and other configuration information, as described in Section 5.5.2 of RFC 4862. Those IPv6 nodes that do not use DHCP for address assignment can ignore the 'M' flag in Router Advertisements.

The method by which IPv6 nodes that use DHCP to obtain other configuration information can obtain other configuration information upon receipt of a Router Advertisement with the \'O' flag set is described in Section 5.5.3 of RFC 4862. Those IPv6 nodes that use DHCP to obtain other configuration information initiate DHCP for other configuration information upon receipt of a Router Advertisement with the 'O' flag set, as described in Section 5.5.3 of RFC 4862. Those IPv6 nodes that do not use DHCP for other configuration information can ignore the 'O' flag in Router Advertisements. An IPv6 node can use the subset of DHCP (described in ) to obtain other configuration information.

Nodes using the Dynamic Host Configuration Protocol for IPv6 (DHCPv6) are expected to determine their default router information and on-link prefix information from received Router Advertisements.

IPv6 nodes MAY support IPv4.

If an IPv6 node implements dual stack and tunneling, then MUST be supported.

The Mobile IPv6 specification defines requirements for the following types of nodes: - mobile nodes - correspondent nodes with support for route optimization - home agents - all IPv6 routers Hosts MAY support mobile node functionality described in Section 8.5 of , including support of generic packet tunneling and secure home agent communications . Hosts SHOULD support route optimization requirements for correspondent nodes described in Section 8.2 of . Routers SHOULD support the generic mobility-related requirements for all IPv6 routers described in Section 8.3 of . Routers MAY support the home agent functionality described in Section 8.4 of , including support of and .

This section describes the specification of IPsec for the IPv6 node.

Security Architecture for the Internet Protocol MUST be supported.

ESP MUST be supported. AH MAY be supported.

Current IPsec RFCs specify the support of transforms and algorithms for use with AH and ESP: NULL encryption, DES-CBC, HMAC-SHA-1-96, and HMAC-MD5-96. However, 'Cryptographic Algorithm Implementation Requirements For ESP and AH' contains the current set of mandatory to implement algorithms for ESP and AH. It also specifies algorithms that should be implemented because they are likely to be promoted to mandatory at some future time. IPv6 nodes SHOULD conform to the requirements in , as well as the requirements specified below. Since ESP encryption and authentication are both optional, support for the NULL encryption algorithm and the NULL authentication algorithm MUST be provided to maintain consistency with the way these services are negotiated. However, while authentication and encryption can each be NULL, they MUST NOT both be NULL. The NULL encryption algorithm is also useful for debugging. The DES-CBC encryption algorithm SHOULD NOT be supported within ESP. Security issues related to the use of DES are discussed in 'DESDIFF', 'DESINT', and 'DESCRACK'. DES-CBC is still listed as required by the existing IPsec RFCs, but updates to these RFCs will be published in the near future. DES provides 56 bits of protection, which is no longer considered sufficient. The use of the HMAC-SHA-1-96 algorithm within AH and ESP MUST be supported. The use of the HMAC-MD5-96 algorithm within AH and ESP MAY also be supported. The 3DES-CBC encryption algorithm does not suffer from the same security issues as DES-CBC, and the 3DES-CBC algorithm within ESP MUST be supported to ensure interoperability. The AES-128-CBC algorithm MUST also be supported within ESP. AES-128 is expected to be a widely available, secure, and efficient algorithm. While AES-128-CBC is not required by the current IPsec RFCs, it is expected to become required in the future.

An implementation MUST support the manual configuration of the security key and SPI. The SPI configuration is needed in order to delineate between multiple keys. Key management SHOULD be supported. Examples of key management systems include IKEv2 and Kerberos; S/MIME and TLS include key management functions. Where key refresh, anti-replay features of AH and ESP, or on-demand creation of Security Associations (SAs) is required, automated keying MUST be supported. Key management methods for multicast traffic are also being worked on by the MSEC WG.

This section defines general host considerations for IPv6 nodes that act as routers. Currently, this section does not discuss routing-specific requirements.

The IPv6 Router Alert Option is an optional IPv6 Hop-by-Hop Header that is used in conjunction with some protocols (e.g., RSVP or MLD ). The Router Alert option will need to be implemented whenever protocols that mandate its usage are implemented. See Section 4.6.

Sending Router Advertisements and processing Router Solicitation MUST be supported.

Network Management MAY be supported by IPv6 nodes. However, for IPv6 nodes that are embedded devices, network management may be the only possible way of controlling these nodes.

The following two MIBs SHOULD be supported by nodes that support an SNMP agent.

IP Forwarding Table MIB SHOULD be supported by nodes that support an SNMP agent.

IP MIB SHOULD be supported by nodes that support an SNMP agent.

This document does not affect the security of the Internet, but implementations of IPv6 are expected to support a minimum set of security features to ensure security on the Internet. 'IP Security Document Roadmap' is important for everyone to read. The security considerations in RFC 2460 state the following: The security features of IPv6 are described in the Security Architecture for the Internet Protocol . RFC 2401 has been obsoleted by RFC 4301, therefore refer RFC 4301 for the security features of IPv6.

This document 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 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.

This appendix keeps track of the chances from RFC 4294 1. Section 5.1, removed "and DNAME" from the discussion about RFC-3363. 2. RFC 2463 references updated to RFC 4443. 3. RFC 3513 references updated to RFC 4291. 4. RFC 3152 refrrences updated to RFC 3596. 5. RFC 2893 references updated to RFC 4213. 6. AH [RFC-4302] support chanced from MUST to MAY. 7. The reference for RFC 3152 has been deleted, as the RFC has been obsoleted, and has been incorporated into RFC 3596. 8. The reference for RFC 3879 has been reomved as the material from RFC 3879 has been incorporated into RFC 4291.