Hi Jensen,
Thank you for your response.
see comments inline.
On 11.08.2016 19:16, Jensen Zhang wrote:
Hi Hans,
Is it possible to compress the cost map by using routing state
abstraction? I think it is a potential solution.
As far as I understand the routing state abstraction draft, it can be
used to eliminate links e.g. from path-vectors regarding client defined
conditions to reduce the size of the cost-map.
However, I see two potential limitations of routing state abstraction in
full cost maps.
1. Assuming a full mesh cost map where costs from every PID to every PID
are provided, so we have a flow from every PID to every PID. The more
flows, the more fine grained is the routing state abstraction, since the
number of shared links among different flows increases. If no
information should be lost, I think the number of links that could be
eliminated decreases with the number of flows. So, having many flows
will result in little to no size reduction. Please correct me, if I got
this wrong.
2. The computation effort for a large number of PIDs in large networks
might exceed an acceptable limit.
Another solution may be to add a proxy layer to compress and
decompress ALTO protocol messages. It will reduce the communication
time and not change the implementation of ALTO servers and clients.
But compression and decompression will increase extra processing time.
Yes, compression is a way to reduce the size at the cost of extra
processing. It reduces the map size to 3.7MB without and 11MB with
path-vector but keeps the size ratio at 1:3.
Hans
We haven't test such large-scale networks, but it is indeed a problem
which need to be handled.
Best,
Jensen
On Thu, Aug 11, 2016 at 9:08 PM, Hans Seidel <[email protected]
<mailto:[email protected]>> wrote:
Hi Richard, all,
after the ALTO session in Berlin, we shortly talked with Ingmar
about the impact of path-vector on the size of cost maps
especially in large-scale networks.
I carried out some tests with path-vector cost maps based on our
data. Our cost maps are already very large but path-vector maps
are about three times larger (~50 MB vs. ~150 MB in uncompressed
state). In average we have round about 4 hops between two PIDs
which leads to an average path-vector of the same length. ECMP was
not considered in the test but it will certainly further increase
the size of the map.
Our idea to reduce cost map size is to provide topology
information, e.g. with the property map presented in the
unified-props draft, and let the client carry out the path
determination. This means, the ALTO server provides the network,
cost and property map to enable clients to get their desired level
of detail for the path costs.
I also think this approach can coexist with path-vector cost maps.
An ALTO server can provide both cost maps with and without path
vector and a property map providing the topology. This way it is
up to the client whether it wants to save bandwidth and invests
some processing time to perform path determination by itself or it
fetches the full path-vector cost map.
Any thoughts on this?
Cheers
Hans
On 01.08.2016 23:37, Vijay K. Gurbani wrote:
Folks: As the (draft) minutes [1] of IETF 96 reflect, there
was general
consensus on adoption of path vector and routing state abstraction
documents towards the charter deliverable of graph representation
formats in ALTO.
The chairs will like to start a call for adoption of the two
documents
--- https://tools.ietf.org/html/draft-yang-alto-path-vector-03
<https://tools.ietf.org/html/draft-yang-alto-path-vector-03> and
https://tools.ietf.org/html/draft-gao-alto-routing-state-abstraction-03
<https://tools.ietf.org/html/draft-gao-alto-routing-state-abstraction-03>
--- as deliverables towards the charter item.
Note that there remains some ambiguity (in the chair's mind)
on whether,
once adopted, these will proceed as two drafts or whether they
will be
merged in one. The authors of these drafts are urged to provide
clarity on the evolution of these documents.
The call for adoption runs for two weeks, from Mon Aug 1, 2016
to Mon
Aug 15, 2016. This will be a good time to comment on the list and
inform the working group of any issues with adopting these
items, or
whether the working group was remiss in considering other
documents.
Please post to the list. (Even a simple "I support these
documents
towards charter deliverable" is a good indication.)
Thanks,
[1]
https://www.ietf.org/proceedings/96/minutes/minutes-96-alto
<https://www.ietf.org/proceedings/96/minutes/minutes-96-alto>
- vijay
_______________________________________________
alto mailing list
[email protected] <mailto:[email protected]>
https://www.ietf.org/mailman/listinfo/alto
<https://www.ietf.org/mailman/listinfo/alto>
_______________________________________________
alto mailing list
[email protected]
https://www.ietf.org/mailman/listinfo/alto
