dnssdext Draft Charter, rev -02 Group Nam: Extensions for Scalable DNS Service Discovery Acronym: dnssdext Area: Internet Area (int) State: Active Charter: Personnel Chairs: Area Director: Ted Lemon Mailing List Address: dnssdext@ietf.org To Subscribe: dnssdext-request@ietf.org Archive: http://www.ietf.org/mail-archive/web/dnssdext http://www.ietf.org/mail-archive/web/mdnsext (1st/2nd BoF) Jabber Chat Room Address: xmpp:dnssdext@jabber.ietf.org Logs: http://jabber.ietf.org/logs/dnssdext http://jabber.ietf.org/logs/mdnsext (1st BoF) Background ---------- Currently, zero configuration networking protocols are generally used to discover services within the scope of a single link. In particular, the Bonjour protocols suite, comprising mDNS (RFC 6762) and DNS-SD (RFC 6763), are widely used for discovery and resolution of services, as well as names, on a single link. The Bonjour protocol suite is commonly used in many scenarios, including home networks, commercial and campus enterprise networks, and may be of use in certain mesh networks. However, the zero configuration multicast Bonjour protocols are constrained to link-local scope, so can only be used to discover services on the same link. In a typical current home network, which is commonly a single link, users should experience the desired discovery behaviour, because all devices share that link. However, in future multi-link home networks (as envisaged by the homenet WG) and in routed campus or enterprise networks, devices and thus users can only discover services on the same links, which is a significant limitation. This has led to calls, such as those by the Educause petition, to develop an appropriate service discovery solution to span multiple links, or to perform discovery across a wide area, not necessarily on directly connected links, e.g., on links elsewhere on the same site, or links at a remote site. In addition, the "Smart Energy Profile 2 Application Protocol Standard", published by ZigBee Alliance and Homeplug Alliance specifies the Bonjour protocols as its method of zero configuration discovery. However, its use of wireless mesh multi-link subnets and its use across traditional routed networks will require extensions to the Bonjour protocols to allow operation across multiple links. The scenarios in which multi-link service discovery is required may be zero configuration environments, environments where administrative configuration is supported, or a mixture of the two. As demand for service discovery across wider area routed networks grows, some vendors are beginning to ship their own early solutions. It is thus both timely and important that efforts to develop improved, scalable, autonomous service discovery solutions for routed networks are coordinated towards producing a single, standards-based solution. The WG will consider the tradeoffs between reusing/extending existing protocols, and developing entirely new ones. But it is highly desirable that any new solution is backwardly compatible with existing mDNS and DNS-SD deployments. Any solution developed by the dnssdext WG wil not conflict or interfere with the operation of other zero-configuration service and naming protocols such as uPnP or LLMNR. Integration with such protocols is out of scope for this WG. The focus of the WG is to develop a solution for extended, scalable DNS-SD. This work is likely to highlight problems and challenges with naming protocols, as some level of coexistence will be required between local zero configuration name services and those forming part of the global DNS. It is important that these issues are captured and documented for further analysis; solving those problems is however not within the scope of this WG. Working Group Description ------------------------- To that end, the primary goals of the dnssdext WG are as follows: 1. To document a set of requirements for scalable, autonomous DNS-based service discovery in routed, multi-link networks in the following five scenarios: (A) Personal Area networks, e.g., one laptop and one printer. This is the simplest example of a service discovery network, and may or may not have external connectivity. (B) Home networks, as envisaged by the homenet WG, consisting of one or more exit routers, with one or more upstream providers or networks, and an arbitrary internal topology with heterogeneous media where routing is automatically configured. The home network would typically be a single zero configuration administrative domain with a relatively limited number of devices. (C) Wireless 'hotspot' networks, which may include wireless networks made available in public places, or temporary or permanent infrastructures targeted towards meeting or conference style events, e.g., as provided for IETF meetings. In such environments other devices may be more likely to be 'hostile' to the user. (D) Enterprise networks, consisting of larger routed networks, with large numbers of devices, which may be deployments spanning over multiple sites with multiple upstreams, and one more more administrative domains (depending on internal administrative delegation). The large majority of the forwarding and security devices are configured. These may be commercial or academic networks, with differing levels of administrative control over certain devices on the network, and BYOD devices commonplace in the amps scenario. (D) Mesh networks such as RPL/6LoWPAN, multi-link but single prefix networks, which may or may not have external connectivity. The topology may use technologies including 802.11 wireless, HomePlug AV and GP, and ZigBee IP. It is desirable that remote service discovery is supported, e.g., a user being able to discover services in their home network while away from the network, and that co-resident services can be discovered, e.g., a printer on a hotel network while the user is on a separately administered network at the same location. It is also desirable that multiple discovery scopes are supported, from the point of view of announcements and discovery, be the scope 'site', 'building' or 'room'. A user for example may only be interested in devices in the same room. 2. To develop an improved, scalable solution for service discovery that can operate in multi-link networks, where devices may be in neighbouring or non-neighbouring links, applicable to the scenarios above. The solution will consider tradeoffs between reusing/extending existing protocols and developing entirely new protocols. The solution should include documentation or definition of the interfaces that can be implemented, separately to transport of the information. 3. To publish an Informational RFC that documents challenges and problems encountered in the coexistence of zero configuration and global DNS name services in such multi-link networks, which should include consideration of both the name resolution mechanism and the namespace. It is important that the dnssdext WG takes input from stakeholders in the scenarios it is considering. For example, the homenet WG is currently evaluating its own requirements for naming and service discovery; it is up to the homenet WG as to whether it wishes to recommend adoption of the solution developed in the dnssdext WG, but coordination between the WGs is desirable. Deliverables: The WG will produce three documents: an Informational RFC on the requirements for service discovery protocols operating on potentially non-neighbouring multi-link networks as described above; a Standards Track RFC documenting an extended, scalable service discovery solution that is applicable to those scenarios; and an Informational RFC describing the problems arising when developing the extended SD solution and how it affects the integration of local zero configuration and global DNS name services. Milestones: Sep 2013 Formation of the WG Oct 2013 Adopt requirements draft as WG document Jan 2014 Submit requirements draft to the IESG as an Informational RFC Mar 2014 Adopt wide-area service discovery solution draft as WG document Mar 2014 Adopt Informational document on the problems and challenges arising for zeroconf and unicast DNS name services Sep 2014 Submit wide-area service discovery solution draft to the IESG as Standards Track RFC Sep 2014 Submit the zeroconf and unicast DNS "problems and challenges" draft to the IESG as Informational.