ALTO WG W. Roome Internet-Draft Alcatel-Lucent Intended status: Standards Track April 10, 2015 Expires: October 12, 2015 Resource Attributes for ALTO Protocol draft-roome-alto-resource-attr-01 Abstract This document extends the Application-Layer Traffic Optimization (ALTO) Protocol [RFC7285] by defining additional descriptive attributes for the resources offered by an ALTO Server. Status of this Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on October 12, 2015. Copyright Notice Copyright (c) 2015 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 (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. Roome Expires October 12, 2015 [Page 1] Internet-Draft Resource Attributes for ALTO Protocol April 2015 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Attributes Versus Capabilities . . . . . . . . . . . . . . 3 2. Changes To ALTO Protocol . . . . . . . . . . . . . . . . . . . 4 2.1. IRD Entries . . . . . . . . . . . . . . . . . . . . . . . 4 3. Resource Attributes . . . . . . . . . . . . . . . . . . . . . 5 3.1. Attribute Names . . . . . . . . . . . . . . . . . . . . . 5 3.2. Attribute Values . . . . . . . . . . . . . . . . . . . . . 6 3.3. Proposed Resource Attributes . . . . . . . . . . . . . . . 6 3.4. Authoritative Endpoint Sets . . . . . . . . . . . . . . . 7 4. Impact On Existing Clients . . . . . . . . . . . . . . . . . . 8 5. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 8 6. Alternatives And Discussion (Delete if draft is published) . . 9 7. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10 Roome Expires October 12, 2015 [Page 2] Internet-Draft Resource Attributes for ALTO Protocol April 2015 1. Introduction In the ALTO Protocol [RFC7285], the Information Resource Directory (IRD) defines the resources, or services, offered by an ALTO server. An IRD contains one entry for each resource. Each entry provides the information a client needs to use that resource: the URI for the resource, the type of data the server returns, the type of data the client sends (if any), the identifiers of any resources on which this resource depends, and optional capabilities for the resource. However, resources have many additional attributes. For example, a Network Map resource maps PID (Provider-defined Identifier) names to network address prefixes. A small Network Map resource might define 20 PIDs and a total of 100 prefixes, while a large Network Map might have 5,000 PIDs and 500,000 prefixes. A client would like to know the size of the Network Map before retrieving it, but the IRD gives no hint. Also, an ALTO Server might have detailed cost data for a set of network addresses, but only approximate costs (or no cost data at all) for other network addresses. If an ALTO Client wants cost data for a particular network address, and the client knows about several different ALTO Servers, the client would prefer to use the ALTO Server with the best data for that address. But the IRD entries give no hint as to the best server; the client would have to try each server and guess as to which has the most accurate data. This document defines a framework for declaring such attributes in IRD entries, and defines an initial set of attributes. 1.1. Attributes Versus Capabilities The ALTO Protocol already defines a "capabilities" section for IRD entries, so one alternative is simply to define additional capabilities. We prefer not to do that for several reasons: o Capabilities are always defined; the ALTO protocol either requires the IRD entry to specify a value, or else defines a default. Attributes are optional, and do not have defaults. o Capability names are defined by the ALTO protocol; adding a new capability requires a new RFC. Attribute names are managed by IANA, so new attributes can be added without extending the protocol. o Attribute values are approximate, and/or may change frequently. Capabilities are accurate, and should not change unless the resource is redefined. For example, if a capability says a Cost Roome Expires October 12, 2015 [Page 3] Internet-Draft Resource Attributes for ALTO Protocol April 2015 Maps returns a "routingcost" cost metric, it is an error if the resource returns a "hopcount" instead. But the size of a Cost Map may vary from time to time. So if a Cost Map attribute says the map has 500 cost points, a client should interpret that as a guideline, and not be surprised of the actual map has 550 costs. 2. Changes To ALTO Protocol 2.1. IRD Entries Resources attributes are defined by a new field, named "attributes", at the same level as the existing "uri" and "media-type" fields in IRD entries. That is, in [RFC7285] Sec. 9.2.2, IRDResourceEntry is revised as: object { JSONString uri; JSONString media-type; [JSONString accepts;] [Capabilities capabilities;] [ResourceID uses<0..*>;] [Attributes attributes;] // Added } IRDResourceEntry; object { ... } Attributes; // Added Here is an example of an IRD with attributes: Roome Expires October 12, 2015 [Page 4] Internet-Draft Resource Attributes for ALTO Protocol April 2015 ... "resources" : { "my-default-network-map" : { "uri" : "http://alto.example.com/networkmap", "media-type" : "application/alto-networkmap+json", "attributes" : { "pid-count-current" : 50, "prefix-count-current" : 150, "authoritative-prefixes" : { "ipv4": [ "1.2.0.0/16", "3.4.0.0/16" ] }, "authoritative-exclusions" : { "ipv4": [ "1.2.1.0/25" ] } } }, "numerical-routing-cost-map" : { "uri" : "http://alto.example.com/costmap/num/routingcost", "media-type" : "application/alto-costmap+json", "capabilities" : { "cost-type-names" : [ "num-routing" ] }, "uses" : [ "my-default-network-map" ], "attributes" : { "cost-count-current" : 500, "cost-count-range" : [ 250, 750 ] } }, ... 3. Resource Attributes 3.1. Attribute Names An attribute name is encoded as a string. The string MUST be no more than 32 characters, and it MUST NOT contain characters other than US- ASCII alphanumeric characters (U+0030-U+0039, U+0041-U+005A, and U+0061-U+007A), the hyphen ('-', U+002D), the colon (':', U+003A), the low line ('_', U+005F), or the '.' separator (U+002E). The '.' separator is reserved for future use and MUST NOT be used unless specifically indicated by a companion or extension document. Identifiers prefixed with "priv:" are reserved for Private Use [RFC5226] without a need to register with IANA. All other identifiers MUST be registered in the "ALTO Resource Attribute Registry" (see Section 8). For an identifier with the "priv:" Roome Expires October 12, 2015 [Page 5] Internet-Draft Resource Attributes for ALTO Protocol April 2015 prefix, an additional string (e.g., company identifier or random string) MUST follow (i.e., "priv:" only is not a valid identifier) to reduce potential collisions. Section 3.3 defines an initial set of Resource Attributes. 3.2. Attribute Values The type of an attribute value depends on the attribute. When registering an attribute with IANA, the JSON value type MUST be specified. 3.3. Proposed Resource Attributes We propose the following Resource Attributes: pid-count-current: Resource type: Network Map Value type: JSON Number Semantics: The number of PIDs in the current Network Map. prefix-count-current: Resource type: Network Map Value type: JSON Number Semantics: The total number of prefixes in the current Network Map. pid-count-range: Resource type: Network Map Value type: JSON Array with two JSON Numbers Semantics: Low and high values for the number of PIDs in the Network Map. This range SHOULD cover the expected size of the map for the foreseeable future. prefix-count-range: Resource type: Network Map Value type: JSON Array with two JSON Numbers Semantics: Low and high values for the total number of prefixes in the Network Map. This range SHOULD cover the expected size of the map for the foreseeable future. authoritative-prefixes: Resource types: Network Map and Endpoint Cost Map Value type: A JSON Object of type NetworkMapData (Section 11.2.1.6 of [RFC7285]) This resource is authoritative (see Section 3.4) for all endpoints which are covered by a prefix in this set, and which are not covered by a prefix in the "authoritative-exclusions" Roome Expires October 12, 2015 [Page 6] Internet-Draft Resource Attributes for ALTO Protocol April 2015 set. authoritative-exclusions: Resource types: Network Map and Endpoint Cost Map Value type: A JSON Object of type NetworkMapData (Section 11.2.1.6 of [RFC7285]) See the "authoritative-prefixes" resource, above. cost-count-current: Resource type: Cost Map Value type: JSON Number Semantics: The number of cost points in the current Cost Map. Note that although a Cost Map is an NxN matrix, where N is the number of PIDs, a Cost Map is not required to define a cost for every {source,destination} pair. cost-count-range Resource type: Cost Map Value type: JSON Array with two JSON Numbers Semantics: Low and high values for the total number of cost points in the Cost Map. This range SHOULD cover the expected size of the map for the foreseeable future. 3.4. Authoritative Endpoint Sets The set of endpoints defined by the "authoritative-prefixes" and "authoritative-exclusions" attributes are the endpoints for which a resource provides authoritative data. For an ALTO Server provided by an ISP, this will usually be the endpoints of the ISP's customers. While we do not rigorously define "authoritative", in general if a resource is authoritative for a set of endpoints, then: o No other ALTO Server has more accurate data for those endpoints. However, other servers may have equally accurate data. o The ALTO Server SHOULD fully specify the costs for those endpoints. That is, for every endpoint EA in the authoritative set and every other endpoint EX, the associated cost map service(s) SHOULD define the costs from EA to EX and from EX to EA. o PIDs covering endpoints in the authoritative set SHOULD be more detailed (smaller, finer-grained, etc.) than PIDs for other endpoints. We define the authoritative set with two lists of prefixes, one ("authoritative-prefixes") to include a set of endpoint addresses, Roome Expires October 12, 2015 [Page 7] Internet-Draft Resource Attributes for ALTO Protocol April 2015 and the other ("authoritative-exclusions") to exclude some of those addresses. We chose that approach because it is a simple and efficient way to represent the addresses of an ISP's customers. An ISP starts by being granted various address blocks by the appropriate authority. These prefixes form the "authoritative-prefixes" list. Over time, some customers might migrate to other ISPs, and take their addresses with them. Those prefixes form the "authoritative- exceptions" list. This two-level model provides an efficient way to represent a large block of addresses with a few exceptions, and seems to be a good balance between efficiency and simplicity. The prefixes in "authoritative-prefixes" do not necessarily appear directly in the Network Map. As an example, suppose an ISP were allocated 1.0.0.0/8. For the Network Map, the ISP would almost certainly break that large set of addresses into a number of different PIDs, to reflect the ISP's network structure (or at least as much as the ISP wishes to reveal). over 4. Impact On Existing Clients [RFC7285] says that clients MUST ignore any fields they do not recognize. Hence this extension should have no impact on existing ALTO Clients; they should simply ignore the resource attributes. 5. Use Cases Here are brief descriptions of several ways in which clients can take advantage of Resource Attributes: o Advance knowledge of the size of a network or cost map allows an ALTO client to allocate sufficient space to hold the map, or to select the appropriate way to store it. For example, a Cost Map is an NxN matrix, where N is the number of PIDs. But it may be sparse. If the number of costs in the Cost Map is considerably less than the square of the number of PIDs in the associated Network Map, then the client knows in advance that the Cost Map is likely to be sparse, and can use sparse matrix techniques. On the other hand, if the number of costs is close to the square of the number of PIDs, the client knows that there is no advantage in using a sparse matrix. o If an ALTO Server offers several different Network Maps, a client can use the network map size and/or authoritative sets to select the appropriate Network Map. Roome Expires October 12, 2015 [Page 8] Internet-Draft Resource Attributes for ALTO Protocol April 2015 o A client such as a P2P tracker can use the authoritative sets to select the appropriate ALTO Server. For example, suppose the tracker has obtained the IRDs for a number of ALTO Servers, each providing accurate data for a subset of the overall network. When a peer requests a set of peers, the tracker would locate the Network Map (or Endpoint Cost Service) whose authoritative set includes the requesting peer's address. The tracker uses that ALTO resource to evaluate costs between the requestor and the other peers, and returns the peers with the lowest costs. 6. Alternatives And Discussion (Delete if draft is published) Here a few points for which I welcome discussion: o Can anyone suggest a better name than "attributes"? I considered "properties", but that conflicts with Endpoint Properties. Another possibility is "meta", but we have overloaded that name. o I don't like the term "authoritative" to describe the endpoints on which a Network Map is centered. However, I can't think of anything better, and it does seem to accurately reflect the intent. Can anyone suggest an alternative? 7. Security Considerations The attribute mechanism described in this document does not introduce any security considerations not already present in the ALTO Protocol. The attributes defined in Section 3.3 provide information which a client can (with effort, perhaps) deduce from the underlying ALTO resources, and hence they do not introduce any new security considerations either. Other attributes might introduce security issues. If so, those issues should be discussed when the attributes are registered with IANA. 8. IANA Considerations This document defines a registry for ALTO Resource Attributes. When a new ALTO Resource Attribute is defined and accepted by the ALTO working group, requests for IANA registration MUST include the identifier, applicable resource type(s), JSON type and intended semantics. Section 3.3 defines the initial set of Resource Attributes. Roome Expires October 12, 2015 [Page 9] Internet-Draft Resource Attributes for ALTO Protocol April 2015 9. References [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", RFC 5226, BCP 26, May 2008. [RFC7285] Almi, 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. Author's Address Wendy Roome Alcatel-Lucent/Bell Labs 600 Mountain Ave, Rm 3B-324 Murray Hill, NJ 07974 USA Phone: +1-908-582-7974 Email: w.roome@alcatel-lucent.com Roome Expires October 12, 2015 [Page 10]