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Internet Engineering Task Force (IETF) S. KieselRequest for Comments: 7286 University of StuttgartCategory: Standards Track M. StiemerlingISSN: 2070-1721 NEC Europe Ltd. N. Schwan Thales Deutschland M. Scharf Alcatel-Lucent Bell Labs H. Song Huawei November 2014Application-Layer Traffic Optimization (ALTO) Server DiscoveryAbstract The goal of Application-Layer Traffic Optimization (ALTO) is to provide guidance to applications that have to select one or several hosts from a set of candidates capable of providing a desired resource. ALTO is realized by a client-server protocol. Before an ALTO client can ask for guidance, it needs to discover one or more ALTO servers. This document specifies a procedure for resource-consumer-initiated ALTO server discovery, which can be used if the ALTO client is embedded in the resource consumer.Status of This Memo This is an Internet Standards Track document. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available inSection 2 of RFC 5741. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc7286.Kiesel, et al. Standards Track [Page 1]

RFC 7286                  ALTO Server Discovery            November 2014Copyright Notice   Copyright (c) 2014 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Table of Contents1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .31.1.  Terminology and Requirements Language . . . . . . . . . .32.  ALTO Server Discovery Procedure Overview  . . . . . . . . . .33.  ALTO Server Discovery Procedure Specification . . . . . . . .43.1.  Step 1: Retrieving the Domain Name  . . . . . . . . . . .53.1.1.  Step 1, Option 1: Local Configuration . . . . . . . .53.1.2.  Step 1, Option 2: DHCP  . . . . . . . . . . . . . . .53.2.  Step 2: U-NAPTR Resolution  . . . . . . . . . . . . . . .64.  Deployment Considerations . . . . . . . . . . . . . . . . . .74.1.  Issues with Home Gateways . . . . . . . . . . . . . . . .7     4.2.  Issues with Multihoming, Mobility, and Changing IP           Addresses . . . . . . . . . . . . . . . . . . . . . . . .75.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .86.  Security Considerations . . . . . . . . . . . . . . . . . . .96.1.  Integrity of the ALTO Server's URI  . . . . . . . . . . .96.2.  Availability of the ALTO Server Discovery Procedure . . .116.3.  Confidentiality of the ALTO Server's URI  . . . . . . . .116.4.  Privacy for ALTO Clients  . . . . . . . . . . . . . . . .127.  References  . . . . . . . . . . . . . . . . . . . . . . . . .127.1.  Normative References  . . . . . . . . . . . . . . . . . .127.2.  Informative References  . . . . . . . . . . . . . . . . .13   Acknowledgments   . . . . . . . . . . . . . . . . . . . . . . . .14   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .14   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .15Kiesel, et al.               Standards Track                    [Page 2]

RFC 7286                  ALTO Server Discovery            November 20141.  Introduction   The goal of Application-Layer Traffic Optimization (ALTO) is to   provide guidance to applications that have to select one or several   hosts from a set of candidates capable of providing a desired   resource [RFC5693].  ALTO is realized by a client-server protocol;   see requirement AR-1 in [RFC6708].  Before an ALTO client can ask for   guidance it needs to discover one or more ALTO servers that can   provide guidance to this specific client.   This document specifies a procedure for resource-consumer-initiated   ALTO server discovery, which can be used if the ALTO client is   embedded in the resource consumer.  In other words, this document   meets requirement AR-32 in [RFC6708] while AR-33 is out of scope.  A   different approach, which tries to meet requirement AR-33, i.e.,   third-party ALTO server discovery, is addressed in [3PDISC].   A more detailed discussion of various options on where to place the   functional entities comprising the overall ALTO architecture can be   found in [ALTO-DEPLOY].   The ALTO protocol specification [RFC7285] is based on HTTP and   expects the discovery procedure to yield the HTTP(S) URI of an ALTO   server's Information Resource Directory (IRD).  Therefore, this   procedure is based on a combination of the Dynamic Host Configuration   Protocol (DHCP) or local configuration and URI-enabled Naming   Authority Pointer (U-NAPTR) resource records in the Domain Name   System (DNS), in order to deliver such URIs.1.1.  Terminology and Requirements Language   This document makes use of the ALTO terminology defined in [RFC5693].   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 inRFC 2119 [RFC2119].2.  ALTO Server Discovery Procedure Overview   The ALTO protocol specification [RFC7285] expects that the ALTO   discovery procedure yields the HTTP(S) URI [RFC7230] of the ALTO   server's Information Resource Directory (IRD), which gives further   information about the capabilities and services provided by that ALTO   server.   On hosts with more than one interface or address family (IPv4/v6),   the ALTO server discovery procedure has to be run for every interface   and address family.  For more details seeSection 4.2.Kiesel, et al.               Standards Track                    [Page 3]

RFC 7286 ALTO Server Discovery November 2014 The ALTO server discovery procedure is performed in two steps: 1. One DNS domain name is retrieved for each combination of interface and address family, either by local configuration (e.g., manual input into a menu or configuration file) or by means of DHCP. 2. These DNS domain names are used for U-NAPTR lookups yielding one or more URIs. Further DNS lookups may be necessary to determine the ALTO server's IP address(es). The primary means for retrieving the DNS domain name is DHCP. However, there may be situations where DHCP is not available or does not return a suitable value. Furthermore, there might be situations in which the user wishes to override the value that could be retrieved from DHCP. In these situations, local configuration may be used. Consequently, the algorithm first checks for a locally configured override, before it tries to retrieve a value from DHCP. Typically, but not necessarily, the DNS domain name is the domain name in which the client is located, i.e., a PTR lookup on the client's IP address (according to[RFC1035], Section 3.5 for IPv4 or[RFC3596], Section 2.5 for IPv6) would yield a similar name. However, due to the widespread use of Network Address Translation (NAT), trying to determine the DNS domain name through a PTR lookup on an interface's IP address is not recommended for resource consumer initiated ALTO server discovery (see also [RFC3424]).3. ALTO Server Discovery Procedure Specification As already outlined inSection 2, the ALTO server discovery procedure is performed for every address family on every interface the application considers for communicating with resource providers. First, the algorithm checks for a locally configured domain name, as specified inSection 3.1.1. If no such name was configured, it tries to retrieve one from DHCP, as specified inSection 3.1.2. If still no domain name could be found, the procedure has failed and terminates with an appropriate error code. If one or more domain names were found, they will be used as U-NAPTR/ DDDS (URI-Enabled NAPTR/Dynamic Delegation Discovery Service) [RFC4848] application-unique strings for a DNS lookup, as specified inSection 3.2.Kiesel, et al. Standards Track [Page 4]

RFC 7286 ALTO Server Discovery November 20143.1. Step 1: Retrieving the Domain Name3.1.1. Step 1, Option 1: Local Configuration The preferred way to acquire a domain name related to an interface's point of network attachment is the use of DHCP (seeSection 3.1.2). However, in some network deployment scenarios, there is no DHCP server available. Furthermore, a user may want to use an ALTO service instance provided by an entity that is not the operator of the underlying IP network. Therefore, we allow the user to specify a DNS domain name, for example, in a configuration file option. An example domain name is: my-alternative-alto-provider.example.org Implementations MAY give the user the opportunity (e.g., by means of configuration file options or menu items) to specify an individual domain name for every address family on every interface. Implementations SHOULD allow the user to specify a default name that is used if no more specific name has been configured.3.1.2. Step 1, Option 2: DHCP Network operators may provide the domain name to be used for service discovery within an access network using DHCP.RFC 5986 [RFC5986] defines DHCP IPv4 and IPv6 access network domain name options to identify a domain name that is suitable for service discovery within the access network.RFC 2132 [RFC2132] defines the DHCP IPv4 domain name option. While this option is less suitable, it still may be useful if theRFC 5986 option is not available. For IPv6, the ALTO server discovery procedure MUST try to retrieve DHCP option 57 (OPTION_V6_ACCESS_DOMAIN). If no such option can be retrieved the procedure fails for this interface. For IPv4, the ALTO server discovery procedure MUST try to retrieve DHCP option 213 (OPTION_V4_ACCESS_DOMAIN). If no such option can be retrieved, the procedure SHOULD try to retrieve option 15 (Domain Name). If neither option can be retrieved, the procedure fails for this interface. If a result can be retrieved, it will be used as an input for the next step (U-NAPTR resolution). One example result could be: example.netKiesel, et al. Standards Track [Page 5]

RFC 7286 ALTO Server Discovery November 20143.2. Step 2: U-NAPTR Resolution The first step of the ALTO server discovery procedure (seeSection 3.1) retrieved one or -- in case of multiple interfaces and/ or IPv4/v6 dual-stack operation -- several domain names, which will be used as U-NAPTR/DDDS (URI-Enabled NAPTR/Dynamic Delegation Discovery Service) [RFC4848] application unique strings. An example is: example.net In the second step, the ALTO server discovery procedure uses a U-NAPTR [RFC4848] lookup with the "ALTO" Application Service Tag and either the "http" or the "https" Application Protocol Tag to obtain one or more URIs (indicating protocol, host, and possibly path elements) for the ALTO server's Information Resource Directory. In this document, only the HTTP and HTTPS URI schemes are defined, as the ALTO protocol specification defines the access over both protocols, but no other [RFC7285]. Note that the result can be any valid HTTP(S) URI. The following two U-NAPTR resource records can be used for mapping "example.net" to the HTTPS URIs "https://alto1.example.net/ird" and "https://alto2.example.net/ird", with the former being preferred. example.net. IN NAPTR 100 10 "u" "ALTO:https" "!.*!https://alto1.example.net/ird!" "" IN NAPTR 100 20 "u" "ALTO:https" "!.*!https://alto2.example.net/ird!" "" If no ALTO-specific U-NAPTR records can be retrieved, the discovery procedure fails for this domain name (and the corresponding interface and IP protocol version). If further domain names retrieved by Step 1 are known, the discovery procedure may perform the corresponding U-NAPTR lookups immediately. However, before retrying a lookup that has failed, a client MUST wait a time period that is appropriate for the encountered error (NXDOMAIN, timeout, etc.).Kiesel, et al. Standards Track [Page 6]

RFC 7286 ALTO Server Discovery November 20144. Deployment Considerations4.1. Issues with Home GatewaysSection 3.1.2 describes the usage of a DHCP option that provides a means for the network operator of the network in which the ALTO client is located to provide a DNS domain name. However, this assumes that this particular DHCP option is correctly passed from the DHCP server to the actual host with the ALTO client, and that the particular host understands this DHCP option. This memo assumes the client to be able to understand the proposed DHCP option; otherwise, there is no further use of the DHCP option, but the client has to use the other proposed mechanisms. There are well-known issues with the handling of DHCP options in home gateways. One issue is that unknown DHCP options are not passed through some home gateways, effectively eliminating the DHCP option. Another well-known issue is the use of home-gateway-specific DNS domain names that "override" the DNS domain name provided by the network operator. For instance, a host behind a home gateway may receive a DNS domain name ".local" instead of "example.net". In general, this domain name is not usable for the server discovery procedure, unless a DNS server in the home gateway resolves the corresponding NAPTR lookup correctly, e.g., by means of a DNS split horizon approach.4.2. Issues with Multihoming, Mobility, and Changing IP Addresses If the user decides to enter only one (default) DNS domain name in the local configuration facility (seeSection 3.1.1), only one set of ALTO servers will be discovered, irrespective of multihoming and mobility. Particularly in mobile scenarios, this can lead to undesirable results. The DHCP-based discovery method can discover different sets of ALTO servers for each interface and address family (i.e., IPv4/v6). In general, if a client wishes to communicate using one of its interfaces and using a specific IP address family, it SHOULD query the ALTO server or servers that have been discovered for this specific interface and address family. How to select an interface and IP address family as well as how to compare results returned from different ALTO servers are out of the scope of this document.Kiesel, et al. Standards Track [Page 7]

RFC 7286 ALTO Server Discovery November 2014 A change of the IP address at an interface invalidates the result of the ALTO server discovery procedure. For instance, if the IP address assigned to a mobile host changes due to host mobility, it is required to re-run the ALTO server discovery procedure without relying on earlier gained information. There are several challenges with DNS on hosts with multiple interfaces [RFC6418], which can affect the ALTO server discovery. If the DNS resolution is performed on the wrong interface, it can return an ALTO server that could provide suboptimal or wrong guidance. Finding the best ALTO server for multi-interfaced hosts is outside the scope of this document. When using Virtual Private Network (VPN) connections, there is usually no DHCP. The user has to enter the DNS domain name in the local configuration facility. For good optimization results, a DNS domain name corresponding to the VPN concentrator, not corresponding to the user's current location, has to be entered. Similar considerations apply for Mobile IP.5. IANA Considerations IANA has registered the following U-NAPTR [RFC4848] application service tag for ALTO: Application Service Tag: ALTO Intended usage: see [RFC5693] or: "The goal of Application-Layer Traffic Optimization (ALTO) is to provide guidance to applications that have to select one or several hosts from a set of candidates capable of providing a desired resource." Defining Publication: The specification contained within this document Contact information: The authors of this document Author/Change controller: The IESG Interoperability considerations: No interoperability issues are known or expected. This tag is to be registered specifically for ALTO, which is a new application without any legacy deployments. Security considerations: seeSection 6 of this document.Kiesel, et al. Standards Track [Page 8]

RFC 7286 ALTO Server Discovery November 2014 Related publications: This document specifies a procedure for discovering an HTTP or HTTPS URI of an ALTO server. HTTP and HTTPS are specified in [RFC7230]. The HTTP(S)-based ALTO protocol is specified in [RFC7285]. Application Protocol Tag: This document specifies how to use the application service tag "ALTO" with the application protocol tags "http" and "https", which have already been registered in the relevant IANA registry. Therefore, IANA is not requested by this document to register any new application protocol tag.6. Security Considerations A high-level discussion of security issues related to ALTO is part of the ALTO problem statement [RFC5693]. A classification of unwanted information disclosure risks, as well as specific security-related requirements can be found in the ALTO requirements document [RFC6708]. The remainder of this section focuses on security threats and protection mechanisms for the ALTO server discovery procedure as such. Once the ALTO server's URI has been discovered and the communication between the ALTO client and the ALTO server starts, the security threats and protection mechanisms discussed in the ALTO protocol specification [RFC7285] apply.6.1. Integrity of the ALTO Server's URI Scenario Description An attacker could compromise the ALTO server discovery procedure or infrastructure in a way that ALTO clients would discover a "wrong" ALTO server URI. Threat Discussion This is probably the most serious security concern related to ALTO server discovery. The discovered "wrong" ALTO server might not be able to give guidance to a given ALTO client at all, or it might give suboptimal or forged information. In the latter case, an attacker could try to use ALTO to affect the traffic distribution in the network or the performance of applications (see alsoSection 15.1. of [RFC7285]). Furthermore, a hostile ALTO server could threaten user privacy (see alsoSection 5.2.1, case (5a) in [RFC6708]). However, it should also be noted that, if an attacker was able to compromise DHCP and/or DNS servers used for ALTO server discovery (see below), (s)he could also launch significantly more serious other attacks (e.g., redirecting various application protocols).Kiesel, et al. Standards Track [Page 9]

RFC 7286 ALTO Server Discovery November 2014 Protection Strategies and Mechanisms The ALTO server discovery procedure consists of three building blocks (local configuration, DHCP, and DNS) and each of them is a possible attack vector. The problem of users possibly following "bad advice" that tricks them into manually configuring unsuitable ALTO servers cannot be solved by technical means and is out of the scope of this document. Due to the nature of the protocol, DHCP is rather prone to attacks. As already mentioned, an attacker that is able to inject forged DHCP replies into the network may do significantly more harm than only configuring a wrong ALTO server. Best current practices for safely operating DHCP should be followed. A further threat is the possible alteration of the DNS records used in U-NAPTR resolution. If an attacker was able to modify or spoof any of the DNS records used in the DDDS resolution, this URI could be replaced by a forged URI. The application of DNS security (DNSSEC) [RFC4033] provides a means to limit attacks that rely on modification of the DNS records used in U-NAPTR resolution. Security considerations specific to U-NAPTR are described in more detail in [RFC4848]. A related risk is the impersonation of the ALTO server (i.e., attacks after the correct URI has been discovered). This threat and protection strategies are discussed inSection 15.1 of [RFC7285]. Note that if Transport Layer Security (TLS) is used to protect ALTO, the server certificate will contain the host name (CN). Consequently, only the host part of the HTTPS URI will be authenticated, i.e., the result of the ALTO server discovery procedure. The U-NAPTR based mapping within the ALTO server discovery procedure needs to be secured as described above, e.g., by using DNSSEC. In addition to active protection mechanisms, users and network operators can monitor application performance and network traffic patterns for poor performance or abnormalities. If it turns out that relying on the guidance of a specific ALTO server does not result in better-than-random outcomes, the use of the ALTO server may be discontinued (see alsoSection 15.2 of [RFC7285]).Kiesel, et al. Standards Track [Page 10]

RFC 7286                  ALTO Server Discovery            November 20146.2.  Availability of the ALTO Server Discovery Procedure   Scenario Description      An attacker could compromise the ALTO server discovery procedure      or infrastructure in a way that ALTO clients would not be able to      discover any ALTO server.   Threat Discussion      If no ALTO server can be discovered (although a suitable one      exists), applications have to make their decisions without ALTO      guidance.  As ALTO could be temporarily unavailable for many      reasons, applications must be prepared to do so.  However, the      resulting application performance and traffic distribution will      correspond to a deployment scenario without ALTO.   Protection Strategies and Mechanisms      Operators should follow best current practices to secure their      DHCP, DNS, and ALTO (seeSection 15.5 of [RFC7285]) servers      against Denial-of-Service (DoS) attacks.6.3.  Confidentiality of the ALTO Server's URI   Scenario Description      An unauthorized party could invoke the ALTO server discovery      procedure, or intercept discovery messages between an authorized      ALTO client and the DHCP and DNS servers, in order to acquire      knowledge of the ALTO server's URI.   Threat Discussion      In the ALTO use cases that have been described in the ALTO problem      statement [RFC5693] and/or discussed in the ALTO working group,      the ALTO server's URI as such has always been considered as public      information that does not need protection of confidentiality.   Protection Strategies and Mechanisms      No protection mechanisms for this scenario have been provided, as      it has not been identified as a relevant threat.  However, if a      new use case is identified that requires this kind of protection,      the suitability of this ALTO server discovery procedure as well as      possible security extensions have to be re-evaluated thoroughly.Kiesel, et al.               Standards Track                   [Page 11]

RFC 7286 ALTO Server Discovery November 20146.4. Privacy for ALTO Clients Scenario Description An unauthorized party could intercept discovery messages between an ALTO client and the DHCP and DNS servers, and thereby find out the fact that said ALTO client uses (or at least tries to use) the ALTO service. Threat Discussion In the ALTO use cases that have been described in the ALTO problem statement [RFC5693] and/or discussed in the ALTO working group, this scenario has not been identified as a relevant threat. Protection Strategies and Mechanisms No protection mechanisms for this scenario have been provided, as it has not been identified as a relevant threat. However, if a new use case is identified that requires this kind of protection, the suitability of this ALTO server discovery procedure as well as possible security extensions have to be re-evaluated thoroughly.7. References7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",BCP 14,RFC 2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions",RFC 2132, March 1997, <http://www.rfc-editor.org/info/rfc2132>. [RFC4848] Daigle, L., "Domain-Based Application Service Location Using URIs and the Dynamic Delegation Discovery Service (DDDS)",RFC 4848, April 2007, <http://www.rfc-editor.org/info/rfc4848>. [RFC5986] Thomson, M. and J. Winterbottom, "Discovering the Local Location Information Server (LIS)",RFC 5986, September 2010, <http://www.rfc-editor.org/info/rfc5986>. [RFC7285] Alimi, R., Penno, R., Yang, Y., Kiesel, S., Previdi, S., Roome, W., Shalunov, S., and R. Woundy, "Application-Layer Traffic Optimization (ALTO) Protocol",RFC 7285, September 2014, <http://www.rfc-editor.org/info/rfc7285>.Kiesel, et al. Standards Track [Page 12]

RFC 7286                  ALTO Server Discovery            November 20147.2.  Informative References   [3PDISC]   Kiesel, S., Krause, K., and M. Stiemerling, "Third-Party              ALTO Server Discovery (3pdisc)", Work in Progress,draft-kist-alto-3pdisc-05, January 2014.   [ALTO-DEPLOY]              Stiemerling, M., Kiesel, S., Previdi, S., and M. Scharf,              "ALTO Deployment Considerations", Work in Progress,draft-ietf-alto-deployments-10, July 2014.   [RFC1035]  Mockapetris, P., "Domain names - implementation and              specification", STD 13,RFC 1035, November 1987,              <http://www.rfc-editor.org/info/rfc1035>.   [RFC3424]  Daigle, L. and IAB, "IAB Considerations for UNilateral              Self-Address Fixing (UNSAF) Across Network Address              Translation",RFC 3424, November 2002,              <http://www.rfc-editor.org/info/rfc3424>.   [RFC3596]  Thomson, S., Huitema, C., Ksinant, V., and M. Souissi,              "DNS Extensions to Support IP Version 6",RFC 3596,              October 2003, <http://www.rfc-editor.org/info/rfc3596>.   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.              Rose, "DNS Security Introduction and Requirements",RFC4033, March 2005,              <http://www.rfc-editor.org/info/rfc4033>.   [RFC5693]  Seedorf, J. and E. Burger, "Application-Layer Traffic              Optimization (ALTO) Problem Statement",RFC 5693, October              2009, <http://www.rfc-editor.org/info/rfc5693>.   [RFC6418]  Blanchet, M. and P. Seite, "Multiple Interfaces and              Provisioning Domains Problem Statement",RFC 6418,              November 2011, <http://www.rfc-editor.org/info/rfc6418>.   [RFC6708]  Kiesel, S., Previdi, S., Stiemerling, M., Woundy, R., and              Y. Yang, "Application-Layer Traffic Optimization (ALTO)              Requirements",RFC 6708, September 2012,              <http://www.rfc-editor.org/info/rfc6708>.   [RFC7230]  Fielding, R. and J. Reschke, "Hypertext Transfer Protocol              (HTTP/1.1): Message Syntax and Routing",RFC 7230, June              2014, <http://www.rfc-editor.org/info/rfc7230>.Kiesel, et al.               Standards Track                   [Page 13]

RFC 7286                  ALTO Server Discovery            November 2014Acknowledgments   Olafur Gudmundsson provided an excellent DNS expert review on an   earlier version of this document.  Thanks to Tina Tsou for an   accurate security review.   Michael Scharf is supported by the German-Lab project   <http://www.german-lab.de> funded by the German Federal Ministry of   Education and Research (BMBF).   Martin Stiemerling is partially supported by the CHANGE project   <http://www.change-project.eu>, a research project supported by the   European Commission under its 7th Framework Program (contract no.   257422).  The views and conclusions contained herein are those of the   authors and should not be interpreted as necessarily representing the   official policies or endorsements, either expressed or implied, of   the CHANGE project or the European Commission.Contributors   The initial version of this document was coauthored by Marco Tomsu.   Hannes Tschofenig provided the initial input to the U-NAPTR solution   part.  Hannes and Martin Thomson provided excellent feedback and   input to the server discovery.   The authors would also like to thank the following persons for their   contribution to this document or its predecessors: Richard Alimi,   David Bryan, Roni Even, Gustavo Garcia, Jay Gu, Xingfeng Jiang,   Enrico Marocco, Victor Pascual, Y. Richard Yang, Yu-Shun Wang, Yunfei   Zhang, Ning Zong.Kiesel, et al.               Standards Track                   [Page 14]

RFC 7286                  ALTO Server Discovery            November 2014Authors' Addresses   Sebastian Kiesel   University of Stuttgart Information Center   Networks and Communication Systems Department   Allmandring 30   Stuttgart  70550   Germany   EMail: ietf-alto@skiesel.de   URI:http://www.rus.uni-stuttgart.de/nks/   Martin Stiemerling   NEC Laboratories Europe   Kurfuerstenanlage 36   Heidelberg  69115   Germany   Phone: +49 6221 4342 113   EMail: mls.ietf@gmail.com   URI:http://ietf.stiemerling.org   Nico Schwan   Thales Deutschland   Thalesplatz 1   Ditzingen  71254   Germany   EMail: ietf@nico-schwan.de   Michael Scharf   Alcatel-Lucent Bell Labs   Lorenzstrasse 10   Stuttgart  70435   Germany   EMail: michael.scharf@alcatel-lucent.com   Haibin Song   Huawei   EMail: haibin.song@huawei.comKiesel, et al.               Standards Track                   [Page 15]

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