Internet Engineering Task Force Erik Guttman INTERNET DRAFT Sun Microsystems 26 October 1998 John Veizades Expires in six months @Home Network Service Location Protocol Modifications for IPv6 draft-ietf-svrloc-ipv6-05.txt Status of this Memo 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.'' 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), ftp.ietf.org (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 [SLP]: 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 [SLPv2]. Guttman, Veizades Expires: 26 May 1999 [Page 1]
Internet Draft Service Location Modifications for IPv6 October 1998 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 Propogation of Link Local Addresses - Address Specification for IPv6 Addresses in URLs - Different multicast addresses 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. 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 [SLP]. Restricted Propogation 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 Guttman, Veizades Expires: 26 May 1999 [Page 2]
Internet Draft Service Location Modifications for IPv6 October 1998 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. Address Specification for IPv6 Addresses in URLs When ever possible the DNS 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 services. A numerical IPv6 address used in a "service:" URL is specified as ipv6-addr = v6num "-" 6( [v6num] "-") v6num ".ipv6" ; Text represented IPv6 address syntax is as ; specified in RFC 2373 [AD6], Section 2.2, ; replacing ':' with '-'. v6num = 1*4HEXDIGIT 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. [IPsec] 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, Veizades Expires: 26 May 1999 [Page 3]
Internet Draft Service Location Modifications for IPv6 October 1998 Assigned numbers for IPv6 The assigned multicast addresses for SLP under IPv4 differ from those in IPv6. These numbers are defined in [MC6]. 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 SLPv1 General Service Location Multicast address and the Directory Agent Discovery Multicast address have been assigned for IPv6, see [MC6]. For SLPv2, only the SVRLOC multicast is used (not the SVRLOC-DA address. These addresses are define in [MC6].) Note that for SLPv2, multicast TTL is not used to limit the propogation of service location multicast requests. Instead, Administratively Scoped multicast addresses [ADM] are used in IPv4 and 'site-local scope' multicast [AD6] is used in IPv6. Acknowledgments Thanks to Dan Harrington, Jim Wood and Alain Durand for their thoughtful reviews of previous drafts of this document. References [DHCP] Droms, R., "Dynamic Host Configuration Protocol", RFC1541, October 1993 [DNS] Mockapetris, P. V. "Domain names - concepts and facilities", RFC 1034. November 1987. Mockapetris, P. V. "Domain names - implementation and specification", RFC 1035. November 1987. [IPsec] Atkinson, R. "IP Authentication Header", RFC 1826, August 1995. Atkinson, R. "IP Encapsulating Security Payload". RFC 1827, August 1995. Atkinson, R. "Security Architecture for the Internet Protocol", RFC 1825, August 1995. [AD6] Hinden, R., Deering, S., "IP Version 6 Addressing Architecture", RFC 2373, July 1998. Guttman, Veizades Expires: 26 May 1999 [Page 4]
Internet Draft Service Location Modifications for IPv6 October 1998 [MC6] Hinden, R., Deering, S., "IPv6 Multicast Address Assignments", RFC 2375, July 1997. [ADM] Meyer, D., "Administratively Scoped IP Multicast", RFC 2365, July 1998. [SLP] Veizades, J., Guttman, E., Perkins, C., Kaplan, S., "Service Location Protocol", RFC 2165, June 1997 [SLPv2] Guttman, E., Perkins, C., Veizades, J., Day, M., "Service Location Protocol, Version 2", draft-ietf-svrloc-protocol-v2-10.txt, October 1998. [SURL] Guttman, E., Perkins, C., Kempf, J., "Service Templates and URLs", draft-ietf-svrloc-service-scheme-12.txt, October 1998, A work in progress. [URL] Berners-Lee, T., Fielding, R., and Masinter, L. "Uniform Resource Identifiers (URI): Generic Syntax", RFC 2396, August 1998. Author Information Erik Guttman Sun Microsystems Bahnstr. 2 74915 Waibstadt Germany Phone: +49 7263 911701 Email: Erik.Guttman@eng.sun.com John Veizades @Home Network 385 Ravendale Dr. Mountain View, CA 94043 Phone: +1 415 944 7332 Fax: +1 415 944 8500 Email: veizades@home.net Guttman, Veizades Expires: 26 May 1999 [Page 5]
