GEOPRIV M. Thomson Internet-Draft J. Winterbottom Intended status: Standards Track Andrew Expires: January 10, 2008 July 9, 2007 Discovering the Local Location Information Server (LIS) draft-thomson-geopriv-lis-discovery-01.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. 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. This Internet-Draft will expire on January 10, 2008. Copyright Notice Copyright (C) The IETF Trust (2007). Thomson & Winterbottom Expires January 10, 2008 [Page 1] Internet-Draft LIS Discovery July 2007 Abstract A method is described for the discovery of a Location Information Server. The method consists of attempting to use a Dynamic Host Configuration Protocol (DHCP) option, followed by a URI-enabled NAPTR (U-NAPTR). DHCP options are defined for both IPv4 and IPv6 DHCP. This document also defines a U-NAPTR Application Service for a LIS, with a specific Application Protocol for the HTTP Enabled Location Delivery (HELD) protocol. Table of Contents 1. Introduction and Overview . . . . . . . . . . . . . . . . . . 3 1.1. DHCP Discovery . . . . . . . . . . . . . . . . . . . . . . 3 1.2. U-NAPTR Discovery . . . . . . . . . . . . . . . . . . . . 3 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 2. LIS Discovery Using DHCP . . . . . . . . . . . . . . . . . . . 5 2.1. DHCPv4 Option for a LIS Address . . . . . . . . . . . . . 5 2.2. DHCPv6 Option for a LIS Address . . . . . . . . . . . . . 5 3. U-NAPTR for LIS Discovery . . . . . . . . . . . . . . . . . . 7 4. Determining the Access Network Domain Name . . . . . . . . . . 8 4.1. DHCP Domain Name Option . . . . . . . . . . . . . . . . . 8 4.2. Reverse DNS . . . . . . . . . . . . . . . . . . . . . . . 8 4.2.1. Determining an External IP Address . . . . . . . . . . 9 5. Recommended Discovery Order . . . . . . . . . . . . . . . . . 11 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7.1. Registration of DHCPv4 and DHCPv6 Option Codes . . . . . . 13 7.2. Registration of a Location Server Application Service Tag . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7.3. Registration of a Location Server Application Protocol Tag for HELD . . . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9.1. Normative References . . . . . . . . . . . . . . . . . . . 16 9.2. Informative References . . . . . . . . . . . . . . . . . . 16 Appendix A. Residential Broadband LCS Discovery Example . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 Intellectual Property and Copyright Statements . . . . . . . . . . 22 Thomson & Winterbottom Expires January 10, 2008 [Page 2] Internet-Draft LIS Discovery July 2007 1. Introduction and Overview Discovering a Location Information Server (LIS) is an important part of the location acquisition process. The LIS is an access network service that needs to be discovered before it can be used. This document describes a method that a host can use to discover a URI for a LIS. The product of a discovery process, such as the one described in this document, is the address of the service. In this document, the result is a URI, which identifies a LIS. A URI permits identification of a LIS that includes information about protocols and other supplementary information. The discovery process requires that the host first attempt LIS discovery using Dynamic Host Configuration protocol (DHCP). If DHCP is not available, or the option is not supported by the network, the host attempts to discover the LIS using the DNS and URI-enabled Naming Authority Pointer (U-NAPTR). Finally, the host can rely on proprietary methods for determining the address of the LIS, including static configuration. 1.1. DHCP Discovery DHCP ([RFC2131], [RFC3315]) is a commonly used mechanism for providing bootstrap configuration information allowing a host to operate in a specific network environment. The bulk of DHCP information is largely static; consisting of configuration information that does not change over the period that the host is attached to the network. Physical location information might change over this time, however the address of the LIS does not. Thus, DHCP is suitable for configuring a host with the address of a LIS. 1.2. U-NAPTR Discovery Where DHCP is not available, the DNS might be able to provide a URI. For DNS methods, alternative discovery techniques SRV records [RFC2782] or Straightforward NAPTR (S-NAPTR) [RFC3958] cannot be used; these methods only permit the return of a hostname and port, not a URI. URI-enabled NAPTR (U-NAPTR) [RFC4848], which is based on S-NAPTR, describes a method of applying the Dynamic Delegation Discovery Service (DDDS) for URI results. For the LIS discovery DDDS application, an Application Service tag "LIS" and an Application Protocol tag "HELD" are created and registered with the IANA. Taking a domain name, this U-NAPTR application uses the two tags to determine the LIS URI. Thomson & Winterbottom Expires January 10, 2008 [Page 3] Internet-Draft LIS Discovery July 2007 Determining the domain name to be used is a critical part of the resolution process. The second part of this document describes how a domain name can be derived. Several methods are described that address different scenarios. 1.3. Terminology 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 [RFC2119]. This document also uses the term "host" to refer to an end host, or Target (in RFC3693 [RFC3693] parlance). The terms "access network" refers to the network that a host connects to for Internet access. The "access network provider" is the entity that operates the access network. The access network provider is responsible for allocating the host an IP address and for directly or indirectly providing a LIS service. Thomson & Winterbottom Expires January 10, 2008 [Page 4] Internet-Draft LIS Discovery July 2007 2. LIS Discovery Using DHCP Where DHCP is available, a host SHOULD attempt to use DHCP to discover the LIS. If the DHCP method fails, the host SHOULD attempt the DNS/U-NAPTR method described in Section 3 or it MAY resort to a configured address. TBD: If multiple protocols can be indicated by these options, how does the host know which protocol is in use? Is there any sense in providing multiple responses for multiple protocols? Possible solution is to reuse the application protocol tag from the U-NAPTR section. 2.1. DHCPv4 Option for a LIS Address This section defines a DHCP for IPv4 (DHCPv4) option for the address of a LIS. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LIS_URI | Length | URI ... . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | URI ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ LIS_URI: The IANA assigned option number (TBD). Length: The length of the URI in octets. URI: The address of the LIS. This URI SHOULD NOT be more than 253 bytes in length, but MAY be extended by concatenating multiple option values, as described in [RFC3396]. The URI MUST NOT be NULL terminated. 2.2. DHCPv6 Option for a LIS Address This section defines a DHCP for IPv6 (DHCPv6) option for the address of a LIS. The DHCPv6 option for this parameter is similarly formatted to the DHCPv4 option. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | OPTION_LIS_URI | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | URI ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Thomson & Winterbottom Expires January 10, 2008 [Page 5] Internet-Draft LIS Discovery July 2007 OPTION_LIS_URI: The IANA assigned option number (TBD). Length: The length of the URI in octets. URI: The address of the LIS. The URI MUST NOT be NULL terminated. Thomson & Winterbottom Expires January 10, 2008 [Page 6] Internet-Draft LIS Discovery July 2007 3. U-NAPTR for LIS Discovery U-NAPTR resolution for a LIS takes a domain name as input and produces a URI that identifies the LIS. This process also requires an Application Service tag and an Application Protocol tag, which differentiate LIS-related NAPTR records from other records for that domain. Section 7.2 defines an Application Service tag of "LIS", which is used to identify the location service for a particular domain. The Application Protocol tag "HELD", defined in Section 7.3, is used to identify a LIS that understands the HELD protocol [I-D.ietf-geopriv-http-location-delivery]. The NAPTR records in the following example demonstrate the use of the Application Service and Protocol tags. Iterative NAPTR resolution is used to delegate responsibility for the LIS service from "zonea.example.com" and "zoneb.example.com" to "example.com". zonea.example.com. ;; order pref flags IN NAPTR 100 10 "" "LIS:HELD" ( ; service "" ; regex example.com. ; replacement ) zoneb.example.com. ;; order pref flags IN NAPTR 100 10 "" "LIS:HELD" ( ; service "" ; regex example.com. ; replacement ) example.com. ;; order pref flags IN NAPTR 100 10 "u" "LIS:HELD" ( ; service "!*.!https://lis.example.com/!" ; regex . ; replacement ) Details for the "LIS" Application Service tag and the "HELD" Application Protocol tag are included in Section 7. Thomson & Winterbottom Expires January 10, 2008 [Page 7] Internet-Draft LIS Discovery July 2007 4. Determining the Access Network Domain Name The U-NAPTR discovery method described in Section 3 requires that the domain name applicable to the access network is known. An unconfigured host might not have this information, therefore it must determine this value before the U-NAPTR method can be attempted. This section describes several methods for discovering a domain name for the local access network. Each method should be attempted where applicable until a domain name is derived. If a domain name is successfully derived but that domain name does not produce any U-NAPTR records, alternative methods can be attempted. Reattempting with different methods is particularly applicable when NAT is used, as is shown in Section 4.2.1. 4.1. DHCP Domain Name Option For IP version 4, Dynamic Host Configuration Protocol (DHCP) option 15 [RFC2131] includes the domain name suffix for the host. If DHCP and option 15 are available, this value should be used as input the U-NAPTR procedure. DHCP for IPv6 provides a single domain name suffix that can be used in the same manner, as a described in [I-D.ietf-dhc-dhcpv6-opt-dnsdomain]. Alternatively, a fully qualified domain name (FQDN) for the host might be provided by the server ([RFC4702] for DHCPv4, [RFC4704] for DHCPv6). This domain name can be used as input to the U-NAPTR resolution is derived from the FQDN by removing the first label. If the host has provided a fully qualified domain name using this option, it SHOULD NOT be used - the domain known to the host might not be the same as that of the access network. Either DHCP method SHOULD be attempted first if DHCP is available. Note that this method is only attempted if the LIS address option is not available. 4.2. Reverse DNS DNS "PTR" records in the "in-addr.arpa." domain can be used to determine the domain name of a host, and therefore, the name of the domain for that host. The use of the "in-addr.arpa." domain is described in [RFC1034] and results in the domain name of the host. Likewise, IPv6 hosts use the "ip6.arpa." domain. In the majority of cases, the domain part of this name (everything excluding the first label) is also the domain name for the access network. Assuming that this is true, this domain name can be used as input to the U-NAPTR Thomson & Winterbottom Expires January 10, 2008 [Page 8] Internet-Draft LIS Discovery July 2007 process. For example, if the for "10.1.2.3" address, if the "PTR" record at "3.2.1.10.in-addr.arpa." refers to "host.example.com", this results in a U-NAPTR search for "example.com". The DNS hierarchy does not necessarily directly map onto a network topology (see [RFC4367]; therefore, this method MUST only be used for the domain name determined by removing the first label only. This method assumes that the access network provider also provides the reverse DNS record and they control the domain that is indicated in the "PTR" record. Furthermore, this method might not apply where a host is given a domain name that is different from the domain name of the access network. This might occur in some hosting configurations, such as where a number of web server hosts, with widely varying domain names, are co-located. From the above example, the access network provider allocated "10.1.2.3" to the host; therefore, they also need to control the DNS domain "example.com" and the associated NAPTR records. DNS Security Extensions (DNSSEC) [RFC4033] provides a cryptographic means of validating this association, through data origin authentication. 4.2.1. Determining an External IP Address Reverse DNS relies on knowing the IP address of a host within the access domain. Initially, this SHOULD be attempted using the IP address that is assigned to a local interface on the host. However, when a NAT device is used, the IP address of the NAT device is substituted for the source IP address. If a NAT device exists between the host and the access network, the host does not have any direct way to determine the IP address that it is effectively using within the access network. The IP address of the NAT device and the corresponding domain name can be used to discover the LIS. In order to use reverse DNS in this configuration, the hosts need to know the IP address that the NAT device uses. The following sections describe some possible methods. These methods are particularly useful in residential broadband configurations. A large proportion of residential broadband services employ a NAT device so that several hosts can share the same Internet access. Since the network behind the NAT device are generally very small, both in numbers and geographical area, it isn't necessary for a LIS to operate within that network; the hosts are able to access a LIS in the access network outside of the NAT device. Thomson & Winterbottom Expires January 10, 2008 [Page 9] Internet-Draft LIS Discovery July 2007 4.2.1.1. UPnP If a NAT device complies with the Universal Plug and Play (UPnP) specification [UPnP-IGD-WANIPConnection1], the WANIPConnection part can be used to query the device for its public IP address. The "GetExternalIPAddress" function provides the external address for a particular network connection. UPnP defines a method for discovering UPnP-enabled hosts in a network; the host does not need any prior configuration to employ this method. 4.2.1.2. STUN A host can use the Simple Traversal of UDP NATs (STUN) [I-D.ietf-behave-rfc3489bis] to determine a public IP address. The host uses the "Binding Request" message and the resulting "MAPPED-ADDRESS" parameter that is returned in the response. Using STUN requires cooperation from a publicly accessible STUN server. A domain name needs to be configured at the host for STUN server discovery. 4.2.1.3. Other Options The source IP address in any IP packet can be used to determine the public IP address of a host. While the STUN method uses a small part of a more sophisticated protocol, this principle can be applied using any other protocol. Like STUN, this method requires prior knowledge of the publicly accessible server and the method that it supports. For instance, a publicly accessible host could be configured to respond to a UDP packet on a predefined port; the data of the response could contain the source IP address that was in the request. Alternatively, a HTTP server at a particular URL could be configured to respond to a GET request with a "text/plain" body containing the IP address of the requester. HTTP proxies render this method unusable; in particular, transparent HTTP proxies might affect the results of this method without the knowledge of the host. Thomson & Winterbottom Expires January 10, 2008 [Page 10] Internet-Draft LIS Discovery July 2007 5. Recommended Discovery Order The previous sections described a set of procedures that allow a device to deterime the LIS associated with the local access network. Some networks maintain a topology analgous to an onion and are comprised of layers separating hosts from the Internet through intermediate networks. It is best therefore for a host to discover the LIS logically closest to it, and this can be done by apply an order of precidence to the discovery techniques described earlier. A Device MUST always try to determine the address of the local LIS through DHCP first. In the event that the Device is unable to determine the address of the LIS through a suitable DHCP option, then it MUST proceed to DNS LIS discovery. In the event that DNS LIS discovery techniques fail, a Device SHOULD use a configured LIS address, OR prompt the user of the device to enter the address of the LIS manually. LIS discovery through DNS requires the Device to determine the domain name of the local access network. The Device MUST try to determine this through the DHCP domain name option (15) first. If this option is unavailable, or fails to yield a valid local LIS address then reverse DNS MUST be used. The inner-most LIS in any chain of networks is the LIS being sort. This LIS is asscoiated with an access domain and similarly the IP address used to identify the end-device in the access domain is the IP address that needs to be determined; that is the inner-most IP address MUST be tested first, then the next and so forth. The device MUST therefore try using the IP addressed directly assigned to it, in the event that that fails, it SHOULD try the other alternatives provided in Section 4.2.1. This document does not provide an order of precidence for these remaining options. It is RECOMMENDED, however, that all devices support the limited set of STUN required to determine an IP chain suitable for the purpose of LIS discovery. Thomson & Winterbottom Expires January 10, 2008 [Page 11] Internet-Draft LIS Discovery July 2007 6. Security Considerations The primary attack against the methods described in this document is one that would lead to impersonation of a LIS. The LIS is responsible for providing location information and this information is critical to a number of network services; furthermore, a host does not necessarily have a prior relationship with a LIS. Several methods are described here that can limit the probablity of, or provide some protection against, such an attack. The address of a LIS is usually well-known within an access network; therefore, interception of messages does not introduce any specific concerns. If DHCP is used, the integrity of DHCP options is limited by the security of the channel over which they are provided. Physical security and separation of DHCP messages from other packets are commonplace methods that can reduce the possibility of attack within an access network; alternatively, DHCP authentication [RFC3118] can provide a degree of protection against modification. An attacker could attempt to compromise the U-NAPTR resolution. A description of the security considerations for U-NAPTR applications is included in [RFC4848]. In addition to considerations related to U-NAPTR, it is important to recognize that the output of this is entirely dependent on its input. An attacker who can control the domain name can also control the final URI. Because a number of methods are provided for determining the domain name, a host implementation needs to consider attacks against each of the methods that are used. Reverse DNS is subject to the maintenance of the "in-addr.arpa." or "ip6.arpa." domain and the integrity of the results that it provides. DNSSEC [RFC4033] provides some measures that can improve the reliability of DNS results. In particular, DNSSEC SHOULD be applied to ensure that the reverse DNS record and the resulting domain are provided by the same entity before this method is used. Without this assurance, the host cannot be certain that the access network provider has provided the NAPTR record for the domain name that is provided. Hosts behind NAT devices are also subject to attacks when retrieving their public IP address. [I-D.ietf-behave-rfc3489bis] describes some means of mitigating this attack for STUN. Thomson & Winterbottom Expires January 10, 2008 [Page 12] Internet-Draft LIS Discovery July 2007 7. IANA Considerations 7.1. Registration of DHCPv4 and DHCPv6 Option Codes The IANA is requested to assign an option code for the DHCPv4 option for a LIS address, as described in Section 2.1 of this document. The IANA is requested to assign an option code for the DHCPv6 option for a LIS address, as described in Section 2.2 of this document. 7.2. Registration of a Location Server Application Service Tag This section registers a new S-NAPTR/U-NAPTR Application Service tag for a LIS, as mandated by [RFC3958]. Application Service Tag: LIS Intended usage: Identifies a service that provides a host with its location information. Defining publication: RFCXXXX Related publications: HELD [I-D.ietf-geopriv-http-location-delivery] Contact information: The authors of this document Author/Change controller: The IESG 7.3. Registration of a Location Server Application Protocol Tag for HELD This section registers a new S-NAPTR/U-NAPTR Application Protocol tag for the HELD [I-D.ietf-geopriv-http-location-delivery] protocol, as mandated by [RFC3958]. Application Service Tag: HELD Intended Usage: Identifies the HELD protocol. Applicable Service Tag(s): LIS Terminal NAPTR Record Type(s): U Defining Publication: RFCXXXX Thomson & Winterbottom Expires January 10, 2008 [Page 13] Internet-Draft LIS Discovery July 2007 Related Publications: HELD [I-D.ietf-geopriv-http-location-delivery] Contact Information: The authors of this document Author/Change Controller: The IESG Thomson & Winterbottom Expires January 10, 2008 [Page 14] Internet-Draft LIS Discovery July 2007 8. Acknowledgements The authors would like to thank Leslie Daigle for her work on U-NAPTR; Peter Koch for his feedback on the DNS aspects of this document; Andy Newton for constructive suggestions with regards to document direction. Thomson & Winterbottom Expires January 10, 2008 [Page 15] Internet-Draft LIS Discovery July 2007 9. References 9.1. Normative References [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [RFC3315] Droms, R., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, July 2003. [RFC3396] Lemon, T. and S. Cheshire, "Encoding Long Options in the Dynamic Host Configuration Protocol (DHCPv4)", RFC 3396, November 2002. [RFC4702] Stapp, M., Volz, B., and Y. Rekhter, "The Dynamic Host Configuration Protocol (DHCP) Client Fully Qualified Domain Name (FQDN) Option", RFC 4702, October 2006. [RFC4704] Volz, B., "The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) Client Fully Qualified Domain Name (FQDN) Option", RFC 4704, October 2006. [RFC4848] Daigle, L., "Domain-Based Application Service Location Using URIs and the Dynamic Delegation Discovery Service (DDDS)", RFC 4848, April 2007. [I-D.ietf-dhc-dhcpv6-opt-dnsdomain] Yan, R., "Domain Suffix Option for DHCPv6", draft-ietf-dhc-dhcpv6-opt-dnsdomain-04 (work in progress), June 2007. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 9.2. Informative References [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for specifying the location of services (DNS SRV)", RFC 2782, February 2000. [RFC3118] Droms, R. and W. Arbaugh, "Authentication for DHCP Messages", RFC 3118, June 2001. [RFC3693] Cuellar, J., Morris, J., Mulligan, D., Peterson, J., and Thomson & Winterbottom Expires January 10, 2008 [Page 16] Internet-Draft LIS Discovery July 2007 J. Polk, "Geopriv Requirements", RFC 3693, February 2004. [RFC3958] Daigle, L. and A. Newton, "Domain-Based Application Service Location Using SRV RRs and the Dynamic Delegation Discovery Service (DDDS)", RFC 3958, January 2005. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. Rose, "DNS Security Introduction and Requirements", RFC 4033, March 2005. [RFC4367] Rosenberg, J. and IAB, "What's in a Name: False Assumptions about DNS Names", RFC 4367, February 2006. [I-D.ietf-behave-rfc3489bis] Rosenberg, J., "Session Traversal Utilities for (NAT) (STUN)", draft-ietf-behave-rfc3489bis-06 (work in progress), March 2007. [I-D.ietf-geopriv-http-location-delivery] Barnes, M., "HTTP Enabled Location Delivery (HELD)", draft-ietf-geopriv-http-location-delivery-00 (work in progress), June 2007. [UPnP-IGD-WANIPConnection1] UPnP Forum, "Internet Gateway Device (IGD) Standardized Device Control Protocol V 1.0: WANIPConnection:1 Service Template Version 1.01 For UPnP Version 1.0", DCP 05-001, Nov 2001. Thomson & Winterbottom Expires January 10, 2008 [Page 17] Internet-Draft LIS Discovery July 2007 Appendix A. Residential Broadband LCS Discovery Example This example shows how LCS discovery using U-NAPTR and DNS might be performed in a residential broadband scenario. The assumed network topology for this network is shown in Figure 4. +-------------+ __________ | | ( ) | NAT | ( ACCESS ) +-------+ Home +-- 203.192.188.75 ---( ) | | Router | ( NETWORK ) | | | ( ) | +-------------+ -----+---- | | | __________ +-------+----------+ +----+---------+ ( ) | | | | ( ) | ISP Domaine Name | | DEVICE | ( INTERNET )--------+ my.isp.net | | Internal IP | ( ) | | | 192.168.0.55 | ( ) +------------------+ | | -----+---- +--------------+ | | +------+-------+ | VOICE | | PROVIDER | +--------------+ Figure 4: Example Network Topology In this example, the Device sits behind a home router that also provides a NATting function. The internal address allocation is from the private 192.168.x.x address range, with 192.168.0.55 being allocated to the Device requiring location information. The outbound IP address provided to the home router is public and and belongs to the my.isp.net domain; in this example the IP assigned to the home router is 203.192.188.75. The Device is subscribed to a general Internet voice service that is decoupled from the access provider. The example further assumes that home router's DHCP server was not capable of providing the address of the LCS directly to the Device, and nor was it able to provide a domain name that resulted in an LCS being found. The VSP to which the Device subscribes provides a STUN server, and the address of this STUN server is configured to be used by the Device. The message flows required in order to discover and Thomson & Winterbottom Expires January 10, 2008 [Page 18] Internet-Draft LIS Discovery July 2007 contact the LCS are shown in Figure 5. +--------+ +--------+ +-----+ +-----+ +--------+ | | | HOME | | ISP | | ISP | | VSP | | DEVICE | | ROUTER | | DNS | | LCS | | STUN | | | | | | | | | | SERVER | +---+----+ +----+---+ +--+--+ +--+--+ +---+----+ | | | | | 1 +------------------- STUN Binding Request----------------->| | | | | | |<---------------STUN MAPPED-ADDRESS = 203.192.188.75------+ 2 | | | | | 3 +------RDNS 75.188.192.203----->| | | | .in-addr.arpa | | | | | | | | |<--203-192-188-205.my.isp.net--+ 4 | | | | | | | 5 +----_LIS:HELD._my.isp.net----->| | | | | | | | |<----https://lcs.my.isp.net/---+ 6 | | | | | | | 7 +--------------locationRequest-------------->| | | | | | | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ . . . . . . . . . . Figure 5: LCS Discovery Message Flow 1: The Device makes a STUN binding request to the VSP's STUN server. the address of the STUN server is preconfigured in the Device 2: The STUN server responds with the MAPPED-ADDRESS of the Device, which is the public address of the home router, 203.192.188.75. 3: The Device issues a reverse DNS lookup to the ISP's DNS server. 4: The ISP's DNS responds with the FQDN of the home router, which includes the domain name of the local access network provider; my.isp.net 5: The Device issues a U-NAPTR request to the ISP's DNS server for LCS that can process a HELD request. Thomson & Winterbottom Expires January 10, 2008 [Page 19] Internet-Draft LIS Discovery July 2007 6: The ISP's DNS server responds with the URL of the local LCS 7: Device issues a HELD locationRequest to the LCS... Thomson & Winterbottom Expires January 10, 2008 [Page 20] Internet-Draft LIS Discovery July 2007 Authors' Addresses Martin Thomson Andrew PO Box U40 Wollongong University Campus, NSW 2500 AU Phone: +61 2 4221 2915 Email: martin.thomson@andrew.com URI: http://www.andrew.com/ James Winterbottom Andrew PO Box U40 Wollongong University Campus, NSW 2500 AU Phone: +61 2 4221 2938 Email: james.winterbottom@andrew.com URI: http://www.andrew.com/ Thomson & Winterbottom Expires January 10, 2008 [Page 21] Internet-Draft LIS Discovery July 2007 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Thomson & Winterbottom Expires January 10, 2008 [Page 22]