ALTO WG R. Alimi, Ed. Internet-Draft Yale University Intended status: Standards Track R. Penno, Ed. Expires: June 19, 2010 Juniper Networks Y. Yang, Ed. Yale University December 16, 2009 ALTO Protocol draft-ietf-alto-protocol-01.txt Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 June 19, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Alimi, et al. Expires June 19, 2010 [Page 1] Internet-Draft ALTO Protocol December 2009 Abstract Networking applications today already have access to a great amount of Inter-Provider network topology information. For example, views of the Internet routing table are easily available at looking glass servers and entirely practical to be downloaded by clients. What is missing is knowledge of the underlying network topology from the ISP or Content Provider (henceforth referred as Provider) point of view. In other words, what an Provider prefers in terms of traffic optimization -- and a way to distribute it. The ALTO Service provides information such as preferences of network resources with the goal of modifying network resource consumption patterns while maintaining or improving application performance. This document describes a protocol implementing the ALTO Service. While such service would primarily be provided by the network (i.e., the ISP), content providers and third parties could also operate this service. Applications that could use this service are those that have a choice in connection endpoints. Examples of such applications are peer-to-peer (P2P) and content delivery networks. Requirements Language 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 RFC 2119 [1]. Alimi, et al. Expires June 19, 2010 [Page 2] Internet-Draft ALTO Protocol December 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 1.1. Background and Problem Statement . . . . . . . . . . . . . 5 1.2. Design History and Merged Proposals . . . . . . . . . . . 5 1.3. Solution Benefits . . . . . . . . . . . . . . . . . . . . 5 1.3.1. Service Providers . . . . . . . . . . . . . . . . . . 5 1.3.2. Applications . . . . . . . . . . . . . . . . . . . . . 6 2. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 2.1.1. Endpoint Address . . . . . . . . . . . . . . . . . . . 6 2.1.2. ASN . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.1.3. Network Location . . . . . . . . . . . . . . . . . . . 7 2.2. ALTO Service and Protocol Scope . . . . . . . . . . . . . 7 3. Protocol Structure . . . . . . . . . . . . . . . . . . . . . . 8 3.1. Server Capability . . . . . . . . . . . . . . . . . . . . 9 3.2. Services . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2.1. Map Service . . . . . . . . . . . . . . . . . . . . . 9 3.2.2. Map Filtering Service . . . . . . . . . . . . . . . . 10 3.2.3. Endpoint Property Service . . . . . . . . . . . . . . 10 3.2.4. Ranking Service . . . . . . . . . . . . . . . . . . . 10 4. Network Map . . . . . . . . . . . . . . . . . . . . . . . . . 10 4.1. PID . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 4.2. Example Network Map . . . . . . . . . . . . . . . . . . . 11 5. Cost Map . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 5.1. Cost Attributes . . . . . . . . . . . . . . . . . . . . . 12 5.1.1. Cost Type . . . . . . . . . . . . . . . . . . . . . . 12 5.1.2. Cost Mode . . . . . . . . . . . . . . . . . . . . . . 12 5.2. Cost Map Structure . . . . . . . . . . . . . . . . . . . . 13 5.3. Network Map and Cost Map Dependency . . . . . . . . . . . 13 6. Protocol Overview . . . . . . . . . . . . . . . . . . . . . . 14 6.1. Design Approach . . . . . . . . . . . . . . . . . . . . . 14 6.1.1. Use of Existing Infrastructure . . . . . . . . . . . . 14 6.1.2. ALTO Information Reuse and Redistribution . . . . . . 14 6.2. Message Format . . . . . . . . . . . . . . . . . . . . . . 15 6.2.1. Query Message . . . . . . . . . . . . . . . . . . . . 15 6.2.2. Response Message . . . . . . . . . . . . . . . . . . . 15 6.2.3. Query and Response Body Encoding . . . . . . . . . . . 16 7. Protocol Messaging . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Client Processing . . . . . . . . . . . . . . . . . . . . 16 7.1.1. General Processing . . . . . . . . . . . . . . . . . . 16 7.1.2. General Error Conditions . . . . . . . . . . . . . . . 17 7.2. Server Processing . . . . . . . . . . . . . . . . . . . . 17 7.2.1. Successful Responses . . . . . . . . . . . . . . . . . 17 7.2.2. General Error Conditions . . . . . . . . . . . . . . . 17 7.2.3. Caching Parameters . . . . . . . . . . . . . . . . . . 17 7.3. ALTO Queries . . . . . . . . . . . . . . . . . . . . . . . 18 7.3.1. Server Capability . . . . . . . . . . . . . . . . . . 18 Alimi, et al. Expires June 19, 2010 [Page 3] Internet-Draft ALTO Protocol December 2009 7.3.2. Map Service . . . . . . . . . . . . . . . . . . . . . 18 7.3.3. Map Filtering Service . . . . . . . . . . . . . . . . 19 7.3.4. Endpoint Property Service . . . . . . . . . . . . . . 21 7.3.5. Ranking Service . . . . . . . . . . . . . . . . . . . 22 8. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 23 8.1. ALTO Client Embedded in P2P Tracker . . . . . . . . . . . 23 8.2. ALTO Client Embedded in P2P Client: Numerical Costs . . . 25 8.3. ALTO Client Embedded in P2P Client: Ranking . . . . . . . 26 9. Discussions . . . . . . . . . . . . . . . . . . . . . . . . . 27 9.1. Discovery . . . . . . . . . . . . . . . . . . . . . . . . 27 9.2. Network Address Translation Considerations . . . . . . . . 27 9.3. Mapping IPs to ASNs . . . . . . . . . . . . . . . . . . . 28 9.4. Endpoint and Path Properties . . . . . . . . . . . . . . . 28 9.5. P2P Peer Selection . . . . . . . . . . . . . . . . . . . . 28 9.5.1. Client-based Peer Selection . . . . . . . . . . . . . 29 9.5.2. Server-based Peer Selection . . . . . . . . . . . . . 29 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29 11. Security Considerations . . . . . . . . . . . . . . . . . . . 29 11.1. ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 11.2. ALTO Clients . . . . . . . . . . . . . . . . . . . . . . . 29 11.3. ALTO Information . . . . . . . . . . . . . . . . . . . . . 30 11.4. ALTO Information Redistribution . . . . . . . . . . . . . 30 11.5. Denial of Service . . . . . . . . . . . . . . . . . . . . 31 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 31 12.1. Normative References . . . . . . . . . . . . . . . . . . . 31 12.2. Informative References . . . . . . . . . . . . . . . . . . 31 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 33 Appendix B. Authors . . . . . . . . . . . . . . . . . . . . . . . 33 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 34 Alimi, et al. Expires June 19, 2010 [Page 4] Internet-Draft ALTO Protocol December 2009 1. Introduction 1.1. Background and Problem Statement Today, network information available to applications is mostly from the view of endhosts. There is no clear mechanism to convey information about the network's preferences to applications. By leveraging better network-provided information, applications have potential to become more network-efficient (e.g., reduce network resource consumption) and achieve better application performance (e.g., accelerated download rate). The ALTO Service intends to provide a simple way to convey network information to applications. The goal of this document is to specify a simple and unified protocol that meets the ALTO requirements [5] while providing a migration path for Internet Service Providers (ISP), Content Providers, and clients that have deployed protocols with similar intentions (see below). This document is a work in progress and will be updated with further developments. 1.2. Design History and Merged Proposals The protocol specified here consists of contributions from o P4P [6], [7]; o ALTO Info-Export [8]; o Query/Response [9], [10]; o ATTP [ATTP]. o Proxidor [19]. See Appendix A for a list of people that have contributed significantly to this effort and the projects and proposals listed above. 1.3. Solution Benefits The ALTO Service offers many benefits to both end-users (consumers of the service) and Internet Service Providers (providers of the service). 1.3.1. Service Providers The ALTO Service enables ISPs to influence the peer selection process in distributed applications in order to increase locality of traffic, Alimi, et al. Expires June 19, 2010 [Page 5] Internet-Draft ALTO Protocol December 2009 improve user-experience, amongst others. It also helps ISPs to efficiently engineer traffic that traverses more expensive links such as backbone and transit links, thus allowing a better provisioning of the networking infrastructure. 1.3.2. Applications Applications that use the ALTO Service can benefit in multiple ways. For example, they may no longer need to infer topology information, and some applications can reduce reliance on measuring path performance metrics themselves. They can take advantage of the ISP's knowledge to avoid bottlenecks and boost performance. An example type of application is a Peer-to-Peer overlay where peer selection can be improved by including ALTO information in the selection process. 2. Architecture Two key design objectives of the ALTO Protocol are simplicity and extensibility. At the same time, it introduces additional techniques to address potential scalability and privacy issues. Below we start with an introduction to the terminology. Then we define the overall architecture and how the ALTO Protocol fits into the architecture. 2.1. Terminology We use the following terms defined in [11]: Application, Overlay Network, Peer, Resource, Resource Identifier, Resource Provider, Resource Consumer, Resource Directory, Transport Address, Host Location Attribute, ALTO Service, ALTO Server, ALTO Client, ALTO Query, ALTO Reply, ALTO Transaction, Local Traffic, Peering Traffic, Transit Traffic. We also use the following additional terms: Endpoint Address, ASN, and Network Location. 2.1.1. Endpoint Address An endpoint address represents the communication address of an end point. An endpoint address can be network-attachment based (IP address) or network-attachment agnostic. Common forms of endpoint addresses include IP address, MAC address, overlay ID, and phone number. Alimi, et al. Expires June 19, 2010 [Page 6] Internet-Draft ALTO Protocol December 2009 2.1.2. ASN An Autonomous System Number. 2.1.3. Network Location Network Location is a generic concept denoting a single endpoint or group of endpoints. Whenever we say Network Location, we refer to either a single endpoint or a group of endpoints. 2.2. ALTO Service and Protocol Scope An ALTO Server conveys the network information from the perspective of a network region. We say that the ALTO Server presents its "my- Internet View" [12] of the network region. A network region in this context can be an Autonomous System, an ISP, perhaps a smaller region, or perhaps a set of ISPs; the details depend on the deployment scenario and discovery mechanism. To better understand the ALTO Service and the role of the ALTO Protocol, we show in Figure 1 the overall system architecture. In this architecture, an ALTO Server prepares ALTO Information; an ALTO Client uses ALTO Service Discovery to identify an appropriate ALTO Server; and the ALTO Client requests available ALTO Information from the ALTO Server using the ALTO Protocol. The ALTO Information provided by the ALTO Server can be updated dynamically based on network conditions, or can be seen as a policy which is updated at a larger time-scale. More specifically, the ALTO Information provided by an ALTO Server may be influenced (at the operator's discretion) by other systems. Examples include (but are not limited to) static network configuration databases, dynamic network information, routing protocols, provisioning policies, and interfaces to outside parties. These components are shown in the figure for completeness but outside the scope of this specification. Alimi, et al. Expires June 19, 2010 [Page 7] Internet-Draft ALTO Protocol December 2009 +-------------------------------------------------------------------+ | ISP | | | | +-----------+ | | | Routing | | | +--------------+ | Protocols | | | | Provisioning | +-----------+ | | | Policy | | | | +--------------+\ | | | \ | | | \ | | | +-----------+ \+---------+ +--------+ | | |Dynamic | | ALTO | ALTO Protocol | ALTO | | | |Network |.......| Server | -------------------- | Client | | | |Information| +---------+ +--------+ | | +-----------+ / / | | / ALTO SD Query/Response / | | / / | | +----------+ +--------------+ | | | External | | ALTO Service | | | | Interface| | Discovery | | | +----------+ +--------------+ | | | | | | Figure 1: Basic ALTO Architecture. | | | | +-------------------------------------------------------------------+ | +------------------+ | Third Parties | | | | Content Providers| +------------------+ ALTO Architecture 3. Protocol Structure The ALTO Protocol uses a simple extensible framework to convey network information. In the general framework, the ALTO protocol will convey properties on both Endpoints and paths between network locations. In this document, we focus on a particular endpoint property to denote the location of an endpoint, and provider-defined costs for paths between pairs of network locations. The ALTO Protocol is built on a common transport protocol, messaging Alimi, et al. Expires June 19, 2010 [Page 8] Internet-Draft ALTO Protocol December 2009 structure and encoding, and transaction model. The protocol is subdivided into services of related functionality. ALTO-Core provides the Map Service. Other services can provide additional functionality. There are three such services defined in this document: the Map Filtering Service, Endpoint Property Service, and Ranking Service. Additional services may be defined in the future in companion documents. .-------------------------------------------------------------------. | | | .----------. .---------------. .---------------. .-------------. | | | | | Map Filtering | | Endpont Prop. | | Ranking | | | | | | Service | | Service | | Service | | | | | `---------------' `---------------' `-------------' | | | Server | .-------------------------------------------------. | | |Capability| | Map Service | | | | | | .-------------. .--------------. | | | | | | | Network Map | | Cost Map | | | | | | | `-------------' `--------------' | | | `----------' `-------------------------------------------------' | | | `-------------------------------------------------------------------' Figure 1: ALTO Protocol Structure 3.1. Server Capability The Server Capability Service lists the details on the information that can be provided by an ALTO Server and perhaps other ALTO Servers maintained by the network provider. The configuration includes, for example, details about the operations and cost metrics supported by the ALTO Server. The capability document can be downloaded by ALTO Clients or provisioned into devices. 3.2. Services 3.2.1. Map Service The Map Service provides batch information to ALTO Clients. Two maps are provided in this document. The Network Map (See Section 4) provides the full set of network location groupings defined by the ALTO Server and the endpoints contained with each grouping. The Cost Map (see Section 5) provides costs between the defined groupings. These two maps can be thought of (and implemented as) as simple files with appropriate encoding provided by the ALTO Server. Alimi, et al. Expires June 19, 2010 [Page 9] Internet-Draft ALTO Protocol December 2009 3.2.2. Map Filtering Service Resource constrained ALTO Clients may benefit from query results being filtered at the ALTO Server. This avoids an ALTO Client spending network bandwidth or CPU collecting results and performing client-side filtering. The Map Filtering Service allows ALTO Clients to query for ALTO Server maps based on additional parameters. 3.2.3. Endpoint Property Service This service allows ALTO Clients to look up properties for individual endpoints. An example endpoint property is its network location (its grouping defined by the ALTO Server) or connectivity type (e.g., ADSL, Cable, or FioS). 3.2.4. Ranking Service Some ALTO Clients may also benefit from querying for rankings and costs based on endpoints. The Ranking Service allows an ALTO Server to return either numerical costs or ordinal costs (rankings) for additional network locations types such as Endpoints. 4. Network Map In reality, many endpoints are very close to one another in terms of network connectivity, for example, endpoints on the same site of an enterprise. By treating a group of endpoints together as a single entity in ALTO, we can achieve much greater scalability without loosing critical information. The Network Location endpoint property allows an ALTO Server to group endpoints together to indicate their proximity. The resulting set of groupings is called the ALTO Network Map. The Network Map may also be used to communicate simple preferences. For example, an ISP may prefer that endpoints associated with the same PoP (Point-of-Presence) in a P2P application communicate locally instead of communicating with endpoints in other PoPs. Note that the definition of proximity varies depending on the granularity of the ALTO information configured by the provider. In one deployment, endpoints on the same subnet may be considered close; while in another deployment, endpoints connected to the same PoP may be considered close. Alimi, et al. Expires June 19, 2010 [Page 10] Internet-Draft ALTO Protocol December 2009 4.1. PID Each group can be identified by a provider-defined Network Location identifier called a PID. There can be many different ways of grouping the endpoints and assigning PIDs. A PID is a identifier providing an indirect and network-agnostic way to specify a network aggregation. For example, a PID may be defined (by the ALTO service provider) to denote a subnet, a set of subnets, a metropolitan area, a PoP, an autonomous system, or a set of autonomous systems. Aggregation of endpoints into PIDs can indicate proximity and can improve scalability. In particular, network preferences (costs) may be specified between PIDs, allowing cost information to be more compact and updated at a smaller time scale than the network aggregations themselves. 4.2. Example Network Map Figure 2 illustrates an example Network Map. PIDs are used to identify network-agnostic aggregations. .--------------------------------------------------------. | ALTO Network Map | | | | .--------------------------------. .---------------. | | | NetLoc: PID-1 | | NetLoc: PID-2 | | | | .---------------------------. | | ... | | | | | 128.36.0.0/16 | | `---------------` | | | | .-----------------------. | | | | | | | Endpoint: 128.36.9.8 | | | .---------------. | | | | `-----------------------` | | | NetLoc: PID-3 | | | | `---------------------------` | | ... | | | | .---------------------------. | `---------------` | | | | 130.132.0.0/16 | | | | | | .-----------------------. | | .---------------. | | | | | Endpoint: 130.132.1.2 | | | | NetLoc: PID-4 | | | | | `-----------------------` | | | ... | | | | `---------------------------` | `---------------` | | `--------------------------------` | | | `--------------------------------------------------------` Figure 2: Example Network Map Alimi, et al. Expires June 19, 2010 [Page 11] Internet-Draft ALTO Protocol December 2009 5. Cost Map An ALTO Server indicates preferences amongst network locations in the form of Path Costs. Path Costs are generic costs and can be internally computed by a network provider according to its own needs. An ALTO Cost Map defines Path Costs pairwise amongst sets of source and destination network locations. 5.1. Cost Attributes Path Costs have attributes: o Type: identifies what the costs represent; o Mode: identifies how the costs should be interpreted (numerical or ordinal). Certain queries for Cost Maps allow the ALTO Client to indicate the desired Type and Mode. 5.1.1. Cost Type The Type attribute indicates what the cost represents. For example, an ALTO Server could define costs representing air-miles, hop-counts, or generic routing costs. Cost types are indicated in protocol messages as alphanumeric strings. An ALTO Server MUST at least define the routing cost type denoted by the string 'routingcost'. Note that an ISP may internally compute routing cost using any method it chooses (including air-miles or hop-count). If an ALTO Client requests a Cost Type that is not available, the ALTO Server responds with an error as specified in Section 7.2.2.2. 5.1.2. Cost Mode The Mode attribute indicates how costs should be interpreted. For example, an ALTO Server could return costs that should be interpreted as numerical values or ordinal rankings. It is important to communicate such information to ALTO Clients, as certain operations may not be valid on certain costs returned by an ALTO Server. For example, it is possible for an ALTO Server to return a set of IP addresses with costs indicating a ranking of the IP addresses. Arithmetic operations, such as summation, that would Alimi, et al. Expires June 19, 2010 [Page 12] Internet-Draft ALTO Protocol December 2009 make sense for numerical values, do not make sense for ordinal rankings. ALTO Clients may want to handle such costs differently. Cost Modes are indicated in protocol messages as alphanumeric strings. An ALTO Server MUST at least define the modes 'numerical' and 'ordinal'. If an ALTO Client requests a Cost Mode that is not supported, the ALTO Server MUST reply with costs having Mode either 'numerical' or 'ordinal'. Thus, an ALTO Server must implement at least one of 'numerical' or 'ordinal' Costs, but it may choose which to support. ALTO Clients may choose how to handle such situations. Two particular possibilities are to use the returned costs as-is (e.g., treat numerical costs as ordinal rankings) or ignore the ALTO information altogether. 5.2. Cost Map Structure A query for a Cost Map either explicitly or implicitly includes a list of Source Network Locations and a list of Destination Network Locations. (Note that a Network Location can be an endpoint address or a PID.) Specifically, assume that a query has a list of multiple Source Network Locations, say [Src_1, Src_2, ..., Src_m], and a list of multiple Destination Network Locations, say [Dst_1, Dst_2, ..., Dst_n]. The ALTO Server will return the Path Cost for each communicating pair (i.e., Src_1 -> Dst_1, ..., Src_1 -> Dst_n, ..., Src_m -> Dst_1, ..., Src_m -> Dst_n). We refer to this structure as a Cost Map. If the Cost Mode is 'ordinal', the Path Cost of each communicating pair is relative to the m*n entries. 5.3. Network Map and Cost Map Dependency If a Path Cost query contains any PID in the list of Source Network Locations or the list of Destination Network Locations, we say that the Path Costs are generated based on a particular Network Map (which defines that PID). Version Tags are introduced to ensure that ALTO Clients are able to use consistent information even though the information is provided in two maps. One advantage of separating ALTO information into a Network Map and a Cost Map is that the two components can be updated at different time scales. For example, Network Maps may be stable for a longer time while Cost Maps may be updated to reflect dynamic network conditions. Alimi, et al. Expires June 19, 2010 [Page 13] Internet-Draft ALTO Protocol December 2009 6. Protocol Overview 6.1. Design Approach The ALTO Protocol design uses a RESTful interface with the goal of leveraging current HTTP [2] [3] implementations and infrastructure. ALTO messages are denoted with HTTP Content-Type "application/alto". Message encodings use a structured, text-based format. The exact encoding will be documented in a future revision, as the current focus is overall protocol architecture and operations. These design decisions make the protocol easier to understand and debug, and allows for flexible ALTO Server implementation strategies. More importantly, however, this enables use of existing implementations and infrastructure, and allows for simple caching and redistribution of ALTO information to increase scalability. 6.1.1. Use of Existing Infrastructure An important design consideration for the ALTO Protocol is easy integration with existing applications and infrastructure. As outlined above, HTTP is a natural choice. In particular, this ALTO Protocol design leverages: o the huge installed base of infrastructure, including HTTP caches, o mature software implementations, o the fact that many P2P clients already have an embedded HTTP client, and o authentication and encryption mechanisms in HTTP and SSL. 6.1.2. ALTO Information Reuse and Redistribution ALTO information may be useful to a large number of applications and users. Distributing ALTO information must be efficient and not become a bottleneck. Therefore, the ALTO Protocol specified in this document integrates with existing HTTP caching infrastructure to allow reuse of ALTO information by ALTO Clients and reduce load on ALTO servers. ALTO information may also be cached or redistributed using application-dependent mechanisms, such as P2P DHTs or P2P file- sharing. For example, a full Network Map may be reused by all ALTO Clients using the ALTO Server. Alimi, et al. Expires June 19, 2010 [Page 14] Internet-Draft ALTO Protocol December 2009 6.2. Message Format The ALTO Protocol uses a RESTful design operating over HTTP. Both Query and Response follow the standard format for HTTP Request and Response messages [2] [3]. This section provides an overview of the components of a Query message sent from an ALTO Client to an ALTO Server, as well as the components of a Response message returned by an ALTO Server. Note that if caching or redistribution is used, the Response message may be returned from another (possibly third-party) entity. Reuse and Redistrubution is further discussed in Section 11.4. 6.2.1. Query Message A Query message is generated by an ALTO Client and sent to an ALTO Server. The ALTO Protocol employs the following components of the HTTP request message: Method: Indicates operation requested by the ALTO Client (along with URI Path). URI Path: Indicates the operation requested by the ALTO Client (along with Method). URI Query String Parameters: Indicates parameters for the requested operation. Note that in the messaging specification in Section 7, we abbreviate these as 'URI QS Params'. Order of query string parameters is not specified. Some parameters are restricted in how many times they appear. We use the notation 'min..max' to denote the the minimum and maximum times they may appear, where 'max' may be '*' to denote unbounded. If no parameters are defined for a particular ALTO request message, the query string MUST be empty (and there MUST be no '?' included in the URI Path). Headers: Indicates encoding of the Body. If the HTTP body of the request is non-empty, the Content-Type header MUST be set to "application/alto". Body: Indicates additional request parameters that are not concisely representable as Query String parameters. If no Body is defined for a particular ALTO request message, the HTTP request body MUST be empty. 6.2.2. Response Message A Response message is generated by an ALTO Server, which corresponds to a particular Query message. The ALTO Protocol employs the following components of the HTTP Response message: Alimi, et al. Expires June 19, 2010 [Page 15] Internet-Draft ALTO Protocol December 2009 Status Code: Indicates either success or an error condition. Headers: Indicates encoding of the Body and caching directives. If the HTTP body of the response is non-empty, the Content-Type header MUST be set to "application/alto" Body: Contains data requested by the ALTO Client. 6.2.3. Query and Response Body Encoding When the Body of a Query or Response message is not empty, it MUST contain a properly-encoded message. This section will be updated to include common requirements when an encoding format is decided. 7. Protocol Messaging This section specifies client and server processing, as well as messages in the ALTO Protocol. Details common to ALTO Server processing of all messages is first discussed, followed by details of the individual messages. Note that the primary focus of the current draft is the architecture and protocol operations, and only the structure of messages is specified (without actual message encoding). Additionally, the following details have been omitted for clarity: o protocol version number o transaction ID o map version tags o HTTP URL encoding This section will be updated as revisions are made to protocol details and encodings. 7.1. Client Processing 7.1.1. General Processing The protocol is structured in such a way that, independent of the query type, there are a set of general processing steps. The ALTO Client selects a specific ALTO Server with which to communicate, establishes a TCP connection, and constructs and sends query messages which MUST conform to Section 7.3. In response to query messages, an ALTO Server constructs and sends response messages which also MUST Alimi, et al. Expires June 19, 2010 [Page 16] Internet-Draft ALTO Protocol December 2009 conform to Section 7.3. An ALTO Server MAY support SSL/TLS to implement server and/or client authentication. An ALTO Server also MAY support HTTP Digest authentication. Cookies MUST NOT be used. ALTO Clients and ALTO Servers MUST additionally follow any TCP transport and HTTP processing and encoding considerations. 7.1.2. General Error Conditions In the case that the client does not receive an appropriate response from the server it can choose another server to communicate or fall back to a default behavior (e.g., perform peer selection without the use of ALTO information). 7.2. Server Processing 7.2.1. Successful Responses If a Query message is successfully processed and an ALTO response is generated, the HTTP status code in the response MUST be set to 200. 7.2.2. General Error Conditions This section specifies ALTO Server behavior when it recevies a Query message that cannot be processed due to a problem with processing the Query message itself. 7.2.2.1. Invalid Query Format If any component of the Query message is formatted incorrectly (i.e., it does not follow the formats in Section 7.3), the ALTO Server MUST return HTTP Status Code 400. 7.2.2.2. Unsupported Query If an ALTO Server does not support the operation indicated in the Query message, the ALTO Server MUST return HTTP Status Code 501. 7.2.3. Caching Parameters If the response generated by the ALTO Server is cachable, the ALTO Server MAY include 'Cache-Control' and 'Expires' HTTP headers, enabling it to be cached by intermediary HTTP Caches or the ALTO Client itself. Alimi, et al. Expires June 19, 2010 [Page 17] Internet-Draft ALTO Protocol December 2009 7.3. ALTO Queries 7.3.1. Server Capability The Server Capability query allows an ALTO Client to determine the available operations of a particular ALTO Server This query MUST be supported. 7.3.1.1. Query Method : 'GET' URI Path : '/capability' 7.3.1.2. Example Response Structure { "instance-name": "alto.example.com", "uri": "http:\/\/alto.example.com:6671", "cost": [ {"type":"latency", "units":"ms"}, {"type":"pDistance","units":"scalar"}, {"type":"bandwidth","units":"kbps"} ], "constraint-support": false } 7.3.2. Map Service The Map Service provides batch information to ALTO Clients in the form of two maps: a Network Map and Cost Map. All queries in the Map Service MUST be supported. 7.3.2.1. Network Map The full Network Map is an instantiation of the Reverse Property Lookup where the ALTO Server lists for each PID, the network locations (endpoints) within the PID. 7.3.2.1.1. Query Method : 'GET' URI Path : '/prop/pid/map' Alimi, et al. Expires June 19, 2010 [Page 18] Internet-Draft ALTO Protocol December 2009 7.3.2.1.2. Example Response Structure { "PID1" : [ "128.36.1.0/24", "132.130.1.0/24", "132.130.2.0/24" ], "PID2" : [ "130.132.3.0/24" ], "PID3" : [ "0.0.0.0/0" ] } 7.3.2.2. Cost Map The Map Service Cost Map query is a batch operation in which the ALTO Server returns the Path Cost for each pair of source/destination PID defined by the ALTO Server. The ALTO Server provides costs using the default Cost Type ('routingcost') and default Cost Mode ('numerical'). 7.3.2.2.1. Query Method : 'GET' URI Path : '/cost/pid/map' 7.3.2.2.2. Example Response Structure { "Type": "routingcost", "Mode": "numerical", "Map" : { "PID1": { "PID1": 1, "PID2": 5 , "PID3": 10 }, "PID2": { "PID1": 5 , "PID2": 1 , "PID3": 15 }, "PID3": { "PID1": 20, "PID2": 15, "PID3": 1 } } } 7.3.3. Map Filtering Service The Map Filtering Service allows ALTO Clients to specify filtering criteria to return a subset of the full maps available in the Map Service. The services defined in this section are OPTIONAL. Alimi, et al. Expires June 19, 2010 [Page 19] Internet-Draft ALTO Protocol December 2009 7.3.3.1. Network Map ALTO Clients can query for a subset of the full network map (see Section 7.3.2.1). 7.3.3.1.1. Query Method : 'POST' URI Path : '/prop/pid/filter' 7.3.3.1.2. Example Request Structure POST /prop/pid/filter ... [ "PID1", "PID2" ] 7.3.3.1.3. Example Response Structure { "PID1" : [ "128.36.1.0/24", "132.130.1.0/24", "132.130.2.0/24" ], "PID2" : [ "130.132.3.0/24" ], "PID3" : [ "0.0.0.0/0" ] } 7.3.3.2. Cost Map ALTO Clients can query for the Cost Map (see Section 7.3.2.2) based on additional parameters. 7.3.3.2.1. Query Method : 'POST' URI Path : '/cost/pid/filter' URI QS Params : 'type=[costtype]' (multiplicity: 0..1) 'mode=[costmode]' (multiplicity: 0..1) 'constraint=[constraint]' (multiplicity: 0..*) The 'constraint' parameter is optional and is to be used only if the ALTO service supports it. It allows a client to specify a target numerical cost. The constraint contains two entities: (1) an operator either 'gt' for greater than , 'lt' for less than or 'eq' for equal to with 10 percent on either side, (2) a target numerical cost. The numerical cost is a number that MUST be defined in the units specified in the ALTO service configuration document obtained Alimi, et al. Expires June 19, 2010 [Page 20] Internet-Draft ALTO Protocol December 2009 from ALTO service discovery. If multiple 'constraint' parameters are specified, the ALTO Server assumes they are related to each other with a logical AND. If the query does not specify the 'type' and 'mode' query string parameters, then the server assumes the type to be 'routingcost' and the mode to be 'numerical'. A Query MUST contain no more than one 'type' parameter, and no more than one 'mode' parameter. The request body MAY specify a list of source PIDs, and a list of destination PIDs. If a list is empty, it is interpreted by the ALTO Server as the full set of PIDs. The ALTO Server returns costs between each pair of source/destination PID. 7.3.3.2.2. Example Request Structure POST /cost/pid/filter { "src": [ "PID1" ], "dst": [ "PID1", "PID2", "PID3" ] } 7.3.3.2.3. Example Response Structure { "Type": "routingcost", "Mode": "numerical", "Map" : { "PID1": { "PID1" : 1, "PID2": 5 , "PID3": 10 }, } } 7.3.4. Endpoint Property Service The Endpoint Property Lookup query allows an ALTO Client to query for properties of Endpoints known to the ALTO Server. If the ALTO Server provides the Endpoint Property Service, the ALTO Server MUST define at least the 'pid' property for Endpoints. Additional supported properties can be defined in the Server Capability response. The services defined in this section are OPTIONAL. 7.3.4.1. Query Method : 'POST' URI Path : '/endpoint/m' URI QS Params : 'prop=[propertyname]' (multiplicity: 1..*) Alimi, et al. Expires June 19, 2010 [Page 21] Internet-Draft ALTO Protocol December 2009 The request body includes a list of Endpoints for which the property value should be returned. If the request body is empty, the ALTO Server implicitly assumes that the request contains a single-element list with the Endpoint address of the requesting client. Also note that the 'prop' parameter may be specified multiple times to query for multiple properties simultaneously. For example, the query string could be 'prop=pid&prop=bandwidth'. 7.3.4.2. Example Request Structure POST /endpoint/m?prop=pid ... [ "ipv4:128.36.1.34" ] 7.3.4.3. Example Response Structure { "ipv4:128.36.1.34" : { "pid": "PID1" } } 7.3.5. Ranking Service The Ranking Service allows ALTO Clients to directly supply endpoints to an ALTO Server. The ALTO Server replies with costs (numerical or ordinal) amongst the endpoints. In particular, this service allows lists of Endpoint addresses to be ranked (ordered) by an ALTO Server. The services defined in this section are OPTIONAL. 7.3.5.1. Ranking Query 7.3.5.1.1. Query Method : 'POST' URI Path : '/cost/endpoint/ranking' URI QS Params : 'type=[costtype]' (multiplicity: 0..1) 'mode=[costmode]' (multiplicity: 0..1) 'constraint=[constraint]' (multiplicity: 0..*) The request body includes a list of source and destination endpoints that should be assigned a cost by the ALTO Server. The 'type', 'mode', and 'constraint' parameters behave as specified in Section 7.3.3.2. The request body MUST specify a list of source Endpoints, and a list Alimi, et al. Expires June 19, 2010 [Page 22] Internet-Draft ALTO Protocol December 2009 of destination Endpoints. If the list of source Endpoints is empty (or it is not included), the ALTO Server MUST treat it as if it contained the Endpoint address of the requesting client. The list of destination Endpoints MUST NOT be empty. The ALTO Server returns costs between each pair of source/destination Endpoint. 7.3.5.1.2. Example Request Structure POST /cost/endpoint/ranking?mode=ordinal ... { "src": "ipv4:128.30.24.2" "dst": [ "ipv4:128.30.24.89", "ipv4:12.32.67.3", "ipv4:130.132.33.4" ] } 7.3.5.1.3. Example Response Structure { "Type": "routingcost", "Mode": "ordinal", "Ranking" : { "ipv4:128.30.24.2": { "ipv4:128.30.24.89" : 1, "ipv4:130.132.33.4" : 2, "ipv4:12.32.67.3" : 3 } } } 8. Use Cases The sections below depict typical use cases. 8.1. ALTO Client Embedded in P2P Tracker Many P2P currently-deployed P2P systems use a Tracker to manage swarms and perform peer selection. P2P trackers may currently use a variety of information to perform peer selection to meet application- specific goals. By acting as an ALTO Client, an P2P tracker can use ALTO information as an additional information source to enable more network-efficient traffic patterns and improve application performance. Alimi, et al. Expires June 19, 2010 [Page 23] Internet-Draft ALTO Protocol December 2009 A particular requirement of many P2P trackers is that they must handle a large number of P2P clients. A P2P tracker can obtain and locally store ALTO information (the Network Map and Cost Map) from the ISPs containing the P2P clients, and benefit from the same aggregation of network locations done by ALTO Servers. .---------. (1) Get Network Map .---------------. | | <----------------------> | | | ALTO | | P2P Tracker | | Server | (2) Get Cost Map | (ALTO Client) | | | <----------------------> | | `---------' `---------------' ^ | (3) Get Peers | | (4) Selected Peer | v List .---------. .-----------. | Peer 1 | <-------------- | P2P | `---------' | Client | . (5) Connect to `-----------' . Selected Peers / .---------. / | Peer 50 | <------------------ `---------' Figure 3: ALTO Client Embedded in P2P Tracker Figure 3 shows an example use case where a P2P tracker is an ALTO Client and applies ALTO information when selecting peers for its P2P clients. The example proceeds as follows: 1. The P2P Tracker requests the Network Map covering all PIDs from the ALTO Server using the Network Map query. The Network Map includes the IP prefixes contained in each PID, allowing the P2P tracker to locally map P2P clients into a PIDs. 2. The P2P Tracker requests the Cost Map amongst all PIDs from the ALTO Server. 3. A P2P Client joins the swarm, and requests a peer list from the P2P Tracker. 4. The P2P Tracker returns a peer list to the P2P client. The returned peer list is computed based on the Network Map and Cost Map returned by the ALTO Server, and possibly other information sources. Note that it is possible that a tracker may use only the Network Map to implement hierarchical peer selection by preferring peers within the same PID and ISP. Alimi, et al. Expires June 19, 2010 [Page 24] Internet-Draft ALTO Protocol December 2009 5. The P2P Client connects to the selected peers. Note that the P2P tracker may provide peer lists to P2P clients distributed across multiple ISPs. In such a case, the P2P tracker may communicate with multiple ALTO Servers. 8.2. ALTO Client Embedded in P2P Client: Numerical Costs P2P clients may also utilize ALTO information themselves when selecting from available peers. It is important to note that not all P2P systems use a P2P tracker for peer discovery and selection. Furthermore, even when a P2P tracker is used, the P2P clients may rely on other sources, such as peer exchange and DHTs, to discover peers. When an P2P Client uses ALTO information, it typically queries only the ALTO Server servicing its own ISP. The my-Internet view provided by its ISP's ALTO Server can include preferences to all potential peers. .---------. (1) Get Network Map .---------------. | | <----------------------> | | | ALTO | | P2P Client | | Server | (2) Get Cost Map | (ALTO Client) | | | <----------------------> | | .---------. `---------' `---------------' <- | P2P | .---------. / | ^ ^ | Tracker | | Peer 1 | <-------------- | | \ `---------' `---------' | (3) Gather Peers . (4) Select Peers | | \ . and Connect / .--------. .--------. .---------. / | P2P | | DHT | | Peer 50 | <---------------- | Client | `--------' `---------' | (PEX) | `--------' Figure 4: ALTO Client Embedded in P2P Client Figure 4 shows an example use case where a P2P Client locally applies ALTO information to select peers. The use case proceeds as follows: 1. The P2P Client requests the Network Map covering all PIDs from the ALTO Server servicing its own ISP. 2. The P2P Client requests the Cost Map amongst all PIDs from the ALTO Server. The Cost Map by default specifies numerical costs. Alimi, et al. Expires June 19, 2010 [Page 25] Internet-Draft ALTO Protocol December 2009 3. The P2P Client discovers peers from sources such as Peer Exchange (PEX) from other P2P Clients, Distributed Hash Tables (DHT), and P2P Trackers. 4. The P2P Client uses ALTO information as part of the algorithm for selecting new peers, and connects to the selected peers. 8.3. ALTO Client Embedded in P2P Client: Ranking It is also possible for a P2P Client to offload the selection and ranking process to an ALTO Server. In this use case, the ALTO Client gathers a list of known peers in the swarm, and asks the ALTO Server to rank them. As in the use case using numerical costs, the P2P Client typically only queries the ALTO Server servicing its own ISP. .---------. .---------------. | | | | | ALTO | (2) Get Endpoint Ranking | P2P Client | | Server | <----------------------> | (ALTO Client) | | | | | .---------. `---------' `---------------' <- | P2P | .---------. / | ^ ^ | Tracker | | Peer 1 | <-------------- | | \ `---------' `---------' | (1) Gather Peers . (3) Connect to | | \ . Selected Peers / .--------. .--------. .---------. / | P2P | | DHT | | Peer 50 | <---------------- | Client | `--------' `---------' | (PEX) | `--------' Figure 5: ALTO Client Embedded in P2P Client: Ranking Figure 5 shows an example of this scenario. The use case proceeds as follows: 1. The P2P Client discovers peers from sources such as Peer Exchange (PEX) from other P2P Clients, Distributed Hash Tables (DHT), and P2P Trackers. 2. The P2P Client queries the ALTO Server's Ranking Service, including discovered peers as the set of Destination Endpoints, and indicates the 'ordinal' Cost Mode. The response indicates the ranking of the candidate peers. Alimi, et al. Expires June 19, 2010 [Page 26] Internet-Draft ALTO Protocol December 2009 3. The P2P Client connects to the peers in the order specified in the ranking. 9. Discussions 9.1. Discovery The particular mechanism by which an ALTO Client discovers its ALTO Server is an important component to the ALTO architecture and numerous techniques have been discussed [13] [14]. However, the discovery mechanism is out of scope for this document. Some ISPs have proposed the possibility of delegation, in which an ISP provides information for customer networks which do not wish to run Portal Servers themselves. A consideration for delegation is that customer networks may wish to explicitly configure such delegation. 9.2. Network Address Translation Considerations At this day and age of NAT v4<->v4, v4<->v6 [15], and possibly v6<->v6[16], a protocol should strive to be NAT friendly and minimize carrying IP addresses in the payload, or provide a mode of operation where the source IP address provide the information necessary to the server. The protocol specified in this document provides a mode of operation where the source network location is computed by the ALTO Server (via the Endpoint Property Lookup interface) from the source IP address found in the ALTO Client query packets. This is similar to how some P2P Trackers (e.g., BitTorrent Trackers - see "Tracker HTTP/HTTPS Protocol" in [17]) operate. The ALTO client SHOULD use the Session Traversal Utilities for NAT (STUN) [4] to determine a public IP address to use as a source NL-ID. If using this method, the host MUST use the "Binding Request" message and the resulting "XOR-MAPPED-ADDRESS" parameter that is returned in the response. Using STUN requires cooperation from a publicly accessible STUN server. Thus, the ALTO client also requires configuration information that identifies the STUN server, or a domain name that can be used for STUN server discovery. To be selected for this purpose, the STUN server needs to provide the public reflexive transport address of the host. Alimi, et al. Expires June 19, 2010 [Page 27] Internet-Draft ALTO Protocol December 2009 9.3. Mapping IPs to ASNs It may be desired for the ALTO Protocol to provide ALTO information including ASNs. Thus, ALTO Clients may need to identify the ASN for a Resource Provider to determine the cost to that Resource Provider. Applications can already map IPs to ASNs using information from a BGP Looking Glass. To do so, they must download a file of about 1.5MB when compressed (as of October 2008, with all information not needed for IP to ASN mapping removed) and periodically (perhaps monthly) refresh it. Alternatively, the Network Map query in the Map Filtering Service defined in this document could be extended to map ASNs into a set of IP prefixes. The mappings provided by the ISP would be both smaller and more authoritative. For simplicity of implementation, it's highly desirable that clients only have to implement exactly one mechanism of mapping IPs to ASNs. 9.4. Endpoint and Path Properties An ALTO Server could make available many properties about Endpoints beyond their network location or grouping. For example, connection type, geographical location, and others may be useful to applications. The current draft focuses on network location and grouping, but the protocol may be extended to handle other Endpoint properties. 9.5. P2P Peer Selection This section discusses possible approaches to peer selection using ALTO information (Network Location Identifiers and associated Costs) from an ALTO Server. Specifically, the application must select which peers to use based on this and other sources of information. With this in mind, the usage of ALTO Costs is intentionally flexible, because: Different applications may use the information differently. For example, an application that connects to just one address may have a different algorithm for selecting it than an application that connects to many. Though initial experiments have been conducted [18], more investigation is needed to identify other methods. In addition, the application might account for robustness, perhaps using randomized exploration to determine if it performs better Alimi, et al. Expires June 19, 2010 [Page 28] Internet-Draft ALTO Protocol December 2009 without ALTO information. 9.5.1. Client-based Peer Selection One possibility is for peer selection using ALTO costs to be done entirely by a P2P client. The following are some techniques have been proposed and/or used: o Prefer network locations with lower ordinal rankings (i.e., higher priority) [19] [8]. o Optimistically unchoking low-cost peers with higher probability [8]. 9.5.2. Server-based Peer Selection Another possibility is for ALTO costs to be used by an Application Tracker (e.g., BitTorrent Tracker) when returning peer lists. The following are techniques that have been proposed and/or used: o Using bandwidth matching (e.g., at an Application Tracker) and choosing solution (within bound of optimal) with minimal network cost [18]. 10. IANA Considerations This document request the registration of a new media type: "application/alto" 11. Security Considerations 11.1. ISPs ISPs must be cognizant of the network topology and provisioning information provided through ALTO Interfaces. ISPs should evaluate how much information is revealed and the associated risks. In particular, providing overly fine-grained information may make it easier for attackers to infer network topology. On the other hand, revealing overly coarse-grained information may not provide benefits to network efficiency or performance improvements to ALTO Clients. 11.2. ALTO Clients Applications using the information must be cognizant of the possibility that the information is malformed or incorrect. Other considerations (e.g., relating to application performance) can be Alimi, et al. Expires June 19, 2010 [Page 29] Internet-Draft ALTO Protocol December 2009 found in Section 6 of [11]. ALTO Clients should also be cognizant of revealing Network Location Identifiers (IP addresses or fine-grained PIDs) to the ALTO Server, as doing so may allow the ALTO Server to infer communication patterns. One possibility is for the ALTO Client to only rely on Network Map for PIDs and Cost Map amongst PIDs to avoid passing IP addresses of their peers to the ALTO Server. 11.3. ALTO Information An ALTO Server may optionally use authentication and encryption to protect ALTO information. SSL/TLS can provide encryption as well as authentication of the client and server. HTTP Basic or Digest authentication can provide authentication of the client (combined with SSL/TLS, it can additionally provide encryption and authentication of the server). ISPs should be cognizant that encryption only protects ALTO information until it is decrypted by the intended ALTO Client. Digital Rights Management (DRM) techniques and legal agreements protecting ALTO information are outside of the scope of this document. 11.4. ALTO Information Redistribution It is possible for applications to redistribute ALTO information to improve scalability. Even with such a distribution scheme, ALTO Clients obtaining ALTO information must be able to validate the received ALTO information to ensure that it was actually generated by the correct ALTO Server. Further, to prevent the ALTO Server from being a target of attack, the verification scheme must not require ALTO Clients to contact the ALTO Server to validate every set of information. Note that the redistribution scheme must additionally handle details such as ensuring ALTO Clients retrieve ALTO information from the correct ALTO Server. See [20] and [21] for further discussion. Details of a particular redistribution scheme are outside the scope of this document. To fulfill these requirements, ALTO Information meant to be redistributable contains a digital signature which includes a hash of the ALTO information signed by the ALTO Server's private key. The corresponding public key should either be part of the ALTO information itself, or it could be included in the server capability response. The public key SHOULD include the hostname of the ALTO Server and it SHOULD be signed by a trusted authority. Alimi, et al. Expires June 19, 2010 [Page 30] Internet-Draft ALTO Protocol December 2009 11.5. Denial of Service ISPs should be cognizant of the workload at the ALTO Server generated by certain ALTO Queries, such as certain queries to the Map Filtering Service and Ranking Service. Therefore ISPs should employ security measures such as firewalls to prevent queries originating from unauthorized networks. ISPs should also leverage the fact that the the Map Service allows ALTO Servers to pre-generate maps that can be useful to many ALTO Clients. 12. References 12.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Berners-Lee, T., Fielding, R., and H. Nielsen, "Hypertext Transfer Protocol -- HTTP/1.0", RFC 1945, May 1996. [3] Fielding, R., Gettys, J., Mogul, J., Frystyk, H., Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. [4] Rosenberg, J., Mahy, R., Matthews, P., and D. Wing, "Session Traversal Utilities for (NAT) (STUN)", draft-ietf-behave-rfc3489bis-18 (work in progress), July 2008. 12.2. Informative References [5] Kiesel, S., Popkin, L., Previdi, S., Woundy, R., and Y. Yang, "Application-Layer Traffic Optimization (ALTO) Requirements", draft-kiesel-alto-reqs-01 (work in progress), November 2008. [6] Alimi, R., Pasko, D., Popkin, L., Wang, Y., and Y. Yang, "P4P: Provider Portal for P2P Applications", draft-p4p-framework-00 (work in progress), November 2008. [7] Wang, Y., Alimi, R., Pasko, D., Popkin, L., and Y. Yang, "P4P Protocol Specification", draft-wang-alto-p4p-specification-00 (work in progress), March 2009. [8] Shalunov, S., Penno, R., and R. Woundy, "ALTO Information Export Service", draft-shalunov-alto-infoexport-00 (work in progress), October 2008. Alimi, et al. Expires June 19, 2010 [Page 31] Internet-Draft ALTO Protocol December 2009 [9] Das, S. and V. Narayanan, "A Client to Service Query Response Protocol for ALTO", draft-saumitra-alto-queryresponse-00 (work in progress), March 2009. [10] Das, S., Narayanan, V., and L. Dondeti, "ALTO: A Multi Dimensional Peer Selection Problem", draft-saumitra-alto-multi-ps-00 (work in progress), October 2008. [11] Seedorf, J. and E. Burger, "Application-Layer Traffic Optimization (ALTO) Problem Statement", RFC 5693, October 2009. [12] Yang, Y., Popkin, L., Penno, R., and S. Shalunov, "An Architecture of ALTO for P2P Applications", draft-yang-alto-architecture-00 (work in progress), March 2009. [13] Garcia, G., Tomsu, M., and Y. Wang, "ALTO Discovery Protocols", draft-wang-alto-discovery-00 (work in progress), March 2009. [14] Song, H., Even, R., Pascual, V., and Y. Zhang, "Application- Layer Traffic Optimization (ALTO): Discover ALTO Servers", draft-song-alto-server-discovery-00 (work in progress), March 2009. [15] Baker, F., Li, X., and C. Bao, "Framework for IPv4/IPv6 Translation", draft-baker-behave-v4v6-framework-02 (work in progress), February 2009. [16] Wasserman, M. and F. Baker, "IPv6-to-IPv6 Network Address Translation (NAT66)", draft-mrw-behave-nat66-02 (work in progress), March 2009. [17] "Bittorrent Protocol Specification v1.0", http://wiki.theory.org/BitTorrentSpecification, 2009. [18] H. Xie, YR. Yang, A. Krishnamurthy, Y. Liu, and A. Silberschatz., "P4P: Provider Portal for (P2P) Applications", In SIGCOMM 2008. [19] Akonjang, O., Feldmann, A., Previdi, S., Davie, B., and D. Saucez, "The PROXIDOR Service", draft-akonjang-alto-proxidor-00 (work in progress), March 2009. [20] Yingjie, G., Alimi, R., and R. Even, "ALTO Information Redistribution", draft-gu-alto-redistribution-01 (work in progress), October 2009. [21] Stiemerling, M., "ALTO Information Redistribution Considered Alimi, et al. Expires June 19, 2010 [Page 32] Internet-Draft ALTO Protocol December 2009 Harmful", draft-stiemerling-alto-info-redist-00 (work in progress), August 2009. Appendix A. Acknowledgments First, we would like to thank the following people whose input and involvement was indispensable in achieving this merged proposal: Obi Akonjang (DT Labs/TU Berlin), Saumitra M. Das (Qualcomm Inc.), Syon Ding (China Telecom), Doug Pasko (Verizon), Laird Popkin (Pando Networks), Satish Raghunath (Juniper Networks), Albert Tian (Ericsson/Redback), Yu-Shun Wang (Microsoft), David Zhang (PPLive), Yunfei Zhang (China Mobile). We would also like to thank the following additional people who were involved in the projects that contributed to this merged document: Alex Gerber (AT&T), Chris Griffiths (Comcast), Ramit Hora (Pando Networks), Arvind Krishnamurthy (University of Washington), Marty Lafferty (DCIA), Erran Li (Bell Labs), Jin Li (Microsoft), Y. Grace Liu (IBM Watson), Jason Livingood (Comcast), Michael Merritt (AT&T), Ingmar Poese (DT Labs/TU Berlin), James Royalty (Pando Networks), Damien Saucez (UCL) Thomas Scholl (AT&T), Emilio Sepulveda (Telefonica), Avi Silberschatz (Yale University), Hassan Sipra (Bell Canada), Georgios Smaragdakis (DT Labs/TU Berlin), Haibin Song (Huawei), Oliver Spatscheck (AT&T), See-Mong Tang (Microsoft), Jia Wang (AT&T), Hao Wang (Yale University), Ye Wang (Yale University), Haiyong Xie (Yale University). Appendix B. Authors [[Comment.1: RFC Editor: Please move information in this section to the Authors' Addresses section at publication time.]] Alimi, et al. Expires June 19, 2010 [Page 33] Internet-Draft ALTO Protocol December 2009 Stefano Previdi Cisco Email: sprevidi@cisco.com Stanislav Shalunov BitTorrent Email: shalunov@bittorrent.com Richard Woundy Comcast Richard_Woundy@cable.comcast.com Authors' Addresses Richard Alimi (editor) Yale University Email: richard.alimi@yale.edu Reinaldo Penno (editor) Juniper Networks 1194 N Mathilda Avenue Sunnyvale, CA USA Email: rpenno@juniper.net Y. Richard Yang (editor) Yale University Email: yry@cs.yale.edu Alimi, et al. Expires June 19, 2010 [Page 34]