Hello Wendy,
Although (IMO) metrics cannot be used in a general traffic management
ALTO use-case, such an extension may be important for some deployments.
W dniu 2015-06-01 o 18:29, Wendy Roome pisze:
Thus a client which knows about the strict-mode extension will request
strict mode, and will supply the implicit costs. But a legacy client will
ignore the unknown mode, and will request the numerical mode instead. So
the legacy client still will get a valid geo-distance cost map, with all
the cost points. It just won't be as efficient.
RFC says:
A cost mode is encoded as a string. The string MUST have a value of
either "numerical" or "ordinal".
Thus, a legacy client may break down and discard whole IRD containing
"strict" cost-mode. Clients should ignore unknown fields, but not let
incorrect values go through. Something that may work is adding a new
field "strict-metric" field to CostType and forcing metric-enabled
clients to use cost map filtering service. E.g., IRD may say:
"meta" : {
"cost-types": {
"num-geo": {
"cost-mode" : "numerical",
"cost-metric": "priv:geodistance",
"strict-metric": true
}
}
Then, if a client (any one) GETs a cost map, it will get the full map.
If a legacy client POSTs for a cost map, it should not add
"strict-metric" field if it does not know its meaning. Thus, it will get
all cost pairs again. Finally, a metric-enabled client may POST
POST /costmap/filtered HTTP/1.1
Host: alto.example.com
Content-Type: application/alto-costmapfilter+json
Content-Length: ...
Accept: application/alto-costmap+json,application/alto-error+json
{
"cost-type" : {"cost-mode": "numerical",
"cost-metric": "routingcost",
"strict-metric": true
},
"pids" : { "srcs" : [], "dsts" : [] }
}
to request a reduced version of the full map. Of course, it may still
filter a map by providing PIDs.
Looking forward for further discussion on this topic :-)
Best regards,
Piotr 'GhosT' Wydrych
--
Piotr 'GhosT' Wydrych .. xmpp:wydrych//agh.edu.pl .. http://wydrych.net/
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?
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