Application-Layer Traffic Optimization Working Group Charter
The ALTO working group was established in 2008 to devise a request/response protocol for allowing a host to benefit from a server that is more cognizant of the network infrastructure than the host would be. The working group has developed an HTTP-based protocol (RFC-to-be) to allow hosts to benefit from the network infrastructure by having access to a pair of maps: a topology map and a cost map.
The origins of the ALTO protocol lie in peer-to-peer (P2P) applications, where the host is a peer in a P2P network and desires a rendezvous with other peers for file sharing, real-time communications, etc. It is a testament to the flexibility of the ALTO protocol that it is now being considered as a solution for problems outside the P2P domain, such as in datacenter networks and in content distribution networks (CDN) where exposing abstract topologies helps applications.
To support the emerging new uses of ALTO, certain extensions are being sought. These extensions can be classified as follows:
- (Standards Track) Protocol extensions for reducing the volume on-the-wire data exchange required to align the ALTO server and clients. Extensions under consideration are mechanisms for delivering server-initiated notifications and partial updates of maps. Efforts developed in other working groups such as Websockets and JSON-patch will be considered, as well as bespoke mechanisms specific to the ALTO protocol. - (Standards Track) Extensions to the base ALTO server discov mechanism (RFC-to-be) for deployment in heterogeneous network environments. Mechanisms under consideration are extensions for third-party and anycast-based server discovery. - (Standards Track) Protocol extensions to convey a richer set attributes to allow applications to determine not only "where" to connect but also "when" to connect. Such additional information will be related both to endpoints (e.g. conveying server load and cache geo-location information for CDN use cases) and to endpoint-to-endpoint costs (e.g. bandwidth calendaring to represent time-averaged cost values in datacenter networks). - The working group will specify such extension in coordination with other working groups that are also working on the related use cases (e.g. cdni, i2rs, lmap). - (Informational) A survey of techniques to formalize the struct of a network graph (that can derived from a set of related ALTO network and cost maps) in a format that would facilitate advanced graph computation. Such survey will cover both models used in popular open-source software (e.g. NetworkX, Blueprints) and models being considered in other working groups (e.g. netmod, i2rs). - (Informational) An document on deployment-related issues lessons learned from early implementation experiences.
When the WG considers standardizing information that the ALTO server
could provide, the following criteria are important to ensure real
After these criteria are met, the importance of the data will be considered for prioritizing standardization work, for example the number of operators and clients that are likely to be able to provide or use that particular data. In any case, this WG will not propose standards on how congestion is signaled, remediated, or avoided, and will not deal with information representing instantaneous network state.
Issues related to the specific content exchanged in systems that make
use of ALTO are also excluded from the WG's scope, as is the issue
dealing with enforcing the legality of the content.
Jul 2014 Working Group Last Call for third-party server discovery
Jul 2014 Working Group Last Call for anycast-based server discovery
Jul 2014 Working Group Last Call for partial updates document
Sep 2014 Submit third-party server discovery document
Sep 2014 Submit anycast-based server discovery document
Sep 2014 Submit partial updates document
Sep 2014 Working Group Last Call for deployment considerations
Sep 2014 Working Group Last Call for network graph format survey
Nov 2014 Submit deployment considerations document
Nov 2014 Submit network graph format survey document
Nov 2014 Working Group Last Call for server-initiated notifications
Jan 2015 Submit server-initiated notifications document
Jan 2015 Working Group Last Call for endpoint property extension
Jan 2015 Working Group Last Call for cost property extension document
Mar 2015 Submit endpoint property extension document
Mar 2015 Submit cost property extension document