[ovs-dev] Query regarding OF1.5 Egress tables (EXT-306)

niti Rohilla niti1489 at gmail.com
Mon Aug 17 11:46:42 UTC 2015


We are working on implementation of OF1.5 Egress tables (EXT 306). Kindly
answer the following queries:-

1) In OFPMP_TABLE_FEATURES request two new parameters "command" and
"features" are to be introduced. As per the current implementation of table
features in ovs, only empty request body is supported and the switch
returns an array of "ofp_table_features" structures containing the
capabilities of the currently configured flow tables as reply and for
non-empty requests switch returns an ofp_error_msg with

But for implementing Egress tables we need to send non-empty request body
to configure "command" and "features" of the tables. Can we now modify the
ovs code to process the non-empty table features request and not send the
permission error?

2) Page no. 145 of Openflow Specification 1.5.1.
The command OFPTFC_REPLACE configures the entire pipeline, and the set of
flow tables in the pipeline must match the set in the request, or an error
must be returned (see The capability of all flow tables included
in the request must be updated. In particular, if the requested
configuration does not contain an ofp_table_features structure for one or
more flow tables that the switch supports, these flow tables are to be
removed from the pipeline if the configuration is successfully set.

Kindly explain the above mentioned paragraph. As per our understanding,
pipeline is configured based on the flow table entries (using instruction
goto-table table_id), can you please explain how does OFPTFC_REPLACE
configures or replaces the entire pipeline associated with tables or we are
missing something regarding pipeline processing in ovs?

3) For a table to be a part of pipleline processing is it necessary to
configure either of these flags(OFPTFF_INGRESS_TABLE and
OFPTFF_EGRESS_TABLE). In other words, if none of the flag is set then table
cannot be part of pipeline processing? Please validate this understanding.

Niti Rohilla

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