Multi-Cost ALTO

The information below is for an old version of the document
Document Type Expired Internet-Draft (alto WG)
Authors Sabine Randriamasy  , Wendy Roome  , Nico Schwan 
Last updated 2016-04-21 (latest revision 2015-10-19)
Replaces draft-randriamasy-alto-multi-cost
Stream Internet Engineering Task Force (IETF)
Expired & archived
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This Internet-Draft is no longer active. A copy of the expired Internet-Draft can be found at


The ALTO (Application Layer-Traffic Optimization) Protocol ([RFC7285]) defines several services that return various metrics describing the costs between network endpoints. For example, when downloading a file that is mirrored on several sites, a user application may use these ALTO cost metrics to determine the most efficient mirror site. An ALTO Server may offer a variety of cost metrics, based on latency, bandwidth, hop count, jitter, or whatever else the ALTO Server deems useful. When selecting a mirror site, a client may consider more than one metric, perhaps trading bandwidth for latency. While the base ALTO Protocol allows a client to use more than one cost metric, to do so, the client must request each metric separately. This document defines a new service that allows a client to retrieve several cost metrics with one request, which is considerably more efficient. In addition, this document extends the ALTO constraint tests to allow a user to specify an arbitrary logical combination of tests on several cost metrics.


Sabine Randriamasy (
Wendy Roome (
Nico Schwan (

(Note: The e-mail addresses provided for the authors of this Internet-Draft may no longer be valid.)