+ requirements: draft-kiesel-alto-reqs was discussed during the last two
meetings, but it seems there is still no fundamental agreement in the
WG about the approach the requirements document should adopt. The
situation has now been stale since Minneapolis: if you want to
contribute to this work and have an opinion, this is the very right
time to let the group hear it;
The draft takes mainly the P2P system point of view. A peer/tracker
accesses the ALTO service and gets some info that can enhance peer
selection. This is good for a P2P system, but what's in this for the
provider of the ALTO service? In the current draft, info seems to flow
only from the ALTO service to the P2P system. I feel that there is (or
should be) a reverse flow of info as well: the P2P system informs the
provider of the ALTO service (realistically, a network operator) about
P2P system traffic, so that the operator can do efficient traffic
management. This might be the missing, complementary incentive that will
make deployment and use of an ALTO service logical for both players: P2P
systems and operators.
Also, to reflect the varying needs of P2P systems and their users, I
think there must be a way for an ALTO client to signal to the ALTO
service preferences regarding rating criteria to be used in calculating
recommendations. (I think this has been already proposed by various
people on the list).
Finally, neighboring domains might agree it makes business sense to
optimize P2P traffic in collaboration. An interface between ALTO
services that would facilitate the exchange of (summarized) topological
info to increase the optimization scope of either, would be helpful in
this case.
Specific changes to the draft that reflect the above are:
- Abstract: replace "The goal of Application-Layer Traffic Optimization
(ALTO) is to provide guidance to applications, which have to select one
or several hosts from a set of candidates, that are able to provide a
desired resource. These recommendations shall be based on parameters
that affect performance and efficiency of the data transmission between
the hosts, e.g., the topological distance." with "Lack of network
information at the application layer makes replica selection inefficient
and suboptimal. At the same time, lack of application traffic
information at the network layer makes network resource management
difficult and expensive. The goal of Application-Layer Traffic
Optimization (ALTO) is to guide applications in selecting hosts from a
set of resource-providing candidates, while providing network entities
with information about application traffic."
- sec#2, par#3, add after 1st sentence: "At the same time, ALTO aims in
providing the network with information about P2P traffic, which is
normally hard to attain, in order to help traffic management."
- sec#2, par#4, add after last sentence: "Similarly, it would be
difficult for network entities to acquire application information by
other mechanisms (e.g. Deep Packet Inspection), because of increased
cost or obfuscation of application flows."
- sec#2, par#5, in 1st sentence: replace "provide the ALTO service" with
"facilitate the exchange of information between the application and the
network".
- REQ. 1: replace "queried" with "accessed".
- sec#4.1, add after REQ. 1 and re-number accordingly: "REQ. 2: An ALTO
service MAY implement a well-defined interface, which can be used by
other ALTO Services to extend their scope of optimization."
- sec#4.1, add after REQ. 2 and re-number accordingly: "REQ. 3: The ALTO
clients MUST be able to submit to the ALTO service information that can
be used by network operators to optimize network resource consumption."
- REQ. 4, par#3: remove duplicate "a" before "host".
- REQ. 5: replace "as well as protocol versioning support to clearly
distinguish between incompatible major versions of the protocol." with
"protocol versioning support to clearly distinguish between incompatible
major versions of the protocol, as well as additional modes of operation."
- REQ. 6: replace "MUST" with "SHOULD"; otherwise the ALTO service MUST
preclude non-complying applications.
- REQ. 12: replace "to discard" with "discarded".
- sec#4.2, add after REQ 13 and re-number accordingly: "REQ. 13: The
ALTO protocol MAY have a mechanism by which the ALTO service can specify
the level and precision of application information required from the
ALTO client."
- sec#4.2, add before REQ 14 and re-number accordingly: "REQ. 13: The
ALTO protocol MAY have a mechanism by which the ALTO client can specify
preferences and relative importance of rating criteria to be used by the
ALTO service in calculating recommendations for resource provider
selection."
- sec#5, par#1: replace "The goal of ALTO is to provide guidance to
resource consumers that have to select resource providers." with "The
goal of ALTO is to provide guidance to application resource consumers
that have to select application resource providers, while assisting
network operator in optimizing network resource consumption."
Thanks,
Spiros
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