Internet Engineering Task Force Erik Guttman INTERNET DRAFT Sun Microsystems 9 August 1999 Expires in six months Service Location Protocol Modifications for IPv6 draft-ietf-svrloc-ipv6-06.txt Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC 2026 [1]. This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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.'' The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract The Service Location Protocol provides a scalable framework for the discovery and selection of network services. Using this protocol, computers using IP based networks no longer need so much static configuration of network services for network based applications. This is especially important as computers become more portable, and users less tolerant of or less able to fulfill the demands of network administration. The Service Location Protocol is well defined for use over IPv4 networks [2]. This document defines its use over IPv6 networks. Since this protocol relies on UDP and TCP, the changes to support its use over IPv6 are minor. This document equally applies to SLP, version 2 [3]. Guttman Expires: 9 February 1999 [Page 1] Internet Draft Service Location Modifications for IPv6 August 1999 Table of Contents 1. Protocol Changes . . . . . . . . . . . . . . . . . . . . 2 2. Eliminating support for broadcast SLP requests . . . . . 2 3. Restricted Propagation of Link Local Addresses . . . . . 3 4. Address Specification for IPv6 Addresses in URLs . . . . 3 5. SLP multicast behavior over IPv6 . . . . . . . . . . . . 4 5.1. SLPv1 Multicast Addresses for IPv6 . . . . . . . . . . . 4 5.2. SLPv2 Multicast Addresses for IPv6 . . . . . . . . . . . 5 6. Security Considerations . . . . . . . . . . . . . . . . . 5 Acknowledgments . . . . . . . . . . . . . . . . . . . . . 6 References . . . . . . . . . . . . . . . . . . . . . . . 6 Author's Contact Information . . . . . . . . . . . . . . 7 Full Copyright Statement . . . . . . . . . . . . . . . . 7 1. Protocol Changes The following are changes required to have the Service Location Protocol work over IPv6. These changes include: - Eliminating support for broadcast SLP requests - Restricted Propagation of Link Local Addresses - Address Specification for IPv6 Addresses in URLs - Different multicast addresses 2. Eliminating support for broadcast SLP requests Service Location over IPv4 allows broadcasts to send Service Location request messages. IPv6 makes use of link layer multicast in place of broadcast. Broadcast only configuration for SLP is not supported under IPv6. If a User Agent wishes to make a request to discover Directory Agents or make a request of multiple Service Agents, the User Agent must multicast the request to the appropriate multicast address. Guttman Expires: 9 February 1999 [Page 2] Internet Draft Service Location Modifications for IPv6 August 1999 This change modifies the requirements described in Section 4.6 (Use of TCP, UDP and Multicast in Service Location) and Section 22 (Implementation Requirements) of the Service Location Protocol [2]. 3. Restricted Propagation of Link Local Addresses Link local advertisements MUST NOT be used if the SLP Agent has a routable address. Service advertisements will include routable addresses in this case. Further, without routable addresses all User Agents (UAs), Service Agents (SAs) and Directory Agents (DAs) transmit multicast SLP messages with a TTL of 1: This includes SrvRqst, AttrRqst, SrvTypeRqst and unsolicited DAAdvert messages. This request is transmitted using a link local scope multicast address. If the SA has no routable address it may send a Service Registration to a DA using its Link Local address. This may occur in an environment where there is no router available. This address must be specified in the Service URL using an IPv6 address specification (see below.) A DA or SA MAY return URLs in SrvRply messages which contain link local IPv6 addresses to UAs, but only with several restrictions. First, the DA or SA must not be multihomed. SLP DAs and SAs MUST NOT respond to SLP messages when they are multihomed and use link local addresses. Second, the DA or SA must not be configured with a routable address. Last, the SA and DA must listen only for link local multicast requests. (The DA will listen for multicast DA discovery requests, the SA will listen for various multicast requests.) If multihomed agents or routable addresses are desired for SLP with IPv6, a router MUST be deployed on the network. 4. Address Specification for IPv6 Addresses in URLs When ever possible the DNS [4] name of the service should be used rather than the above representation. Service Location allows the use of the protocol without the benefit of DNS. This is relevant when a group of systems is connected to build a network without any previous configuration of servers to support this network. When Service Location is used in this manner, numerical addresses must be used to identify the location of Guttman Expires: 9 February 1999 [Page 3] Internet Draft Service Location Modifications for IPv6 August 1999 services. The format of a "service:" URL is defined in [5]. This URL is an ``absolute URI'' as defined by [6]. A numerical IPv6 address, such as may be used in a "service:" URL, is specified as in [7]. The textual representation defined for literal IPv6 addresses in [8]: ipv6-addr = "[" num-addr "]" num-addr = ; Text represented IPv6 address syntax is as ; specified in RFC 2373 [8], Section 2.2, Examples: This is a site local scoped address, as could be used in a SLP DAAdvert message. service:directory-agent://[FEC0::A3F9:251C:1291:109D] This is a link local scoped address, as could be used by a SA to advertise its service on a IPv6 network with no routers or DNS service. service:printer:ipp://[FE80::015A:93C0:D85D:B098]:8080/path 5. SLP multicast behavior over IPv6 Since IPv6 offers scoped multicast addresses, these are used instead of setting TTL to 32. In SLPv1, for instance, the default TTL setting was chosen to limit the propagation of discovery messages to a site local network. SLPv1 and SLPv2 agents MUST use the site local scope for transmission of multicast messages, unless configured to use a more restrictive scope (for example, the link local scope). 5.1. SLPv1 Multicast Addresses for IPv6 The assigned multicast addresses for SLPv1 under IPv4 differ from those in IPv6. These numbers are defined in [9]. Their values are: FF0X:0:0:0:0:0:0:116 SVRLOC [Veizades] FF0X:0:0:0:0:0:0:123 SVRLOC-DA [Veizades] FF05:0:0:0:0:0:1:1000 Service Location [RFC2165] -FF05:0:0:0:0:0:1:13FF The SVRLOC-DA address is used by SLPv1 UAs and SAs to discover SLPv1 DAs. The SVRLOC address is used by SLPv1 UAs to multicast requests to SLPv1 SAs. The range of Service Location addresses MAY be used by SLPv1 UAs and MUST be listened for by SLPv1 SAs. This address range is used to distribute Service Request queries over the range Guttman Expires: 9 February 1999 [Page 4] Internet Draft Service Location Modifications for IPv6 August 1999 of addresses. A hashing scheme is used based on the service type of the request, as described in [2]. 5.2 SLPv2 Multicast Addresses for IPv6 SLPv2 for IPv4 specifies only one multicast address. The reason only one address was used, instead of the variety of addresses specified for SLPv1, is that there are only 255 relative assignments available for the Administratively Scoped Addresses [10]. IPv6, on the other hand, has scoped addresses and enough range for static assignments. SLPv2 for IPv6 uses the same addresses as defined for SLPv1. The SVRLOC address is used for the following messages: Service Type Request and Attribute Request messages. The SVRLOC-DA address is used for multicast Service Requests for the "service:directory-agent" service type. DAs send unsolicited DA advertisements to the SVRLOC-DA multicast address. All other multicast SrvRqst messages are sent to the appropriate Service Location multicast address. SAs join the groups which correspond to the Service Types of the services they advertise. The address is determined using the algorithm provided in SLPv1. The Service Type string used in the SrvRqst is hashed to a value from 0-1023. This determines the offset into the FF05::1:1000-13FF range. An unsigned 32 bit value V is initialized to 0. Each byte of the Service Type UTF-8 [11] encoded string value is considered consecutively. First, the value V is multiplied by 33, then the value of the current string byte is added. The result is contained in the low order 10 bits of V. 6. Security Considerations User Agents and Directory Agents may ignore all unauthenticated Service Location messages when a valid IPSec association exists. Service Agents and Directory Agents must be able to use the IP Authentication and IP Encapsulating Security Payload in Service Location messages whenever an appropriate IPSec Security Association exists. [12] SLP allows digital signatures to be produced to allow the verification of the contents of messages. There is nothing in the Modifications for IPv6 document which weakens or strengthens this technique. Guttman Expires: 9 February 1999 [Page 5] Internet Draft Service Location Modifications for IPv6 August 1999 Acknowledgments Thanks to Dan Harrington, Jon Wood and Alain Durand for their thoughtful reviews of previous drafts of this document. John Veizades contributed to the original version of this document. References [1] Bradner, S., "The Internet Standards Process -- Version 3", RFC 2026, October 1996. [2] Veizades, J., Guttman, E., Perkins, C., Kaplan, S., "Service Location Protocol", RFC 2165, June 1997 [3] Guttman, E., Perkins, C., Veizades, J., Day, M., "Service Location Protocol, Version 2", RFC 2608, July 1999. [4] Mockapetris, P. V. "Domain names - concepts and facilities", RFC 1034. November 1987. Mockapetris, P. V. "Domain names - implementation and specification", RFC 1035. November 1987. [5] Guttman, E., Perkins, C., Kempf, J., "Service Templates and URLs", RFC 2609, July 1999. [6] Berners-Lee, T., Fielding, R., and Masinter, L. "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. [7] Hinden, R., Carpenter, B., "Preferred Format for Literal IPv6 Addresses in URL's", , July, 1999. [8] Hinden, R., Deering, S., "IP Version 6 Addressing Architecture", RFC 2373, July 1998. [9] Hinden, R., Deering, S., "IPv6 Multicast Address Assignments", RFC 2375, July 1997. [10] Meyer, D., "Administratively Scoped IP Multicast", RFC 2365, July 1998. [11] Yergeau, F., "UTF-8, a transformation format of ISO 10646", RFC 2279, January 1998. [12] Kent, S., Atkinson, R. "Security Architecture for the Internet Protocol", RFC 2401, November 1998. Guttman Expires: 9 February 1999 [Page 6] Internet Draft Service Location Modifications for IPv6 August 1999 Author's Contact Information Erik Guttman Sun Microsystems Eichhoelzelstr. 7 74915 Waibstadt Germany Phone: +49 7263 911701 Email: Erik.Guttman@germany.sun.com Full Copyright Statement Copyright (C) The Internet Society (1999). All Rights Reserved. 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