[ovs-dev] [PATCH v8] Implement OFPT_TABLE_STATUS Message.

[Saloni Jain]

Hi Ben,

As per the Openflow Specification-1.4, Section: 7.4.3.1 Modify Flow Table Message, Page:73,74:

"When the remaining space in the flow table increases to more than vacancy_up, and if vacancy up events are enabled, a vacancy up event must be generated to the controller using the OFPT_TABLE_STATUS message type with reason OFPTR_VACANCY_UP.

When enabling events, if the current vacancy is less than vacancy_up, vacancy up events must be enabled, and vacancy down events must be disabled."

If current vacancy is same as remaining space(free space), the two statements of the specifications are contradictory.

Please help me in clarifying my doubt regarding these statements.

Thanks and Regards,
Saloni Jain
Tata Consultancy Services
Mailto: saloni.jain at tcs.com
Website: http://www.tcs.com
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-----Ben Pfaff <blp at ovn.org> wrote: -----
To: Saloni Jain <saloni.jain at tcs.com>
From: Ben Pfaff <blp at ovn.org>
Date: 01/13/2016 10:42PM
Cc: dev at openvswitch.org, saloni.jain12 at gmail.com, Deepankar Gupta <deepankar.gupta at tcs.com>, Partha Datta <partha.datta at tcs.com>, rishi.bamba at tcs.com
Subject: Re: [ovs-dev] [PATCH v8] Implement OFPT_TABLE_STATUS Message.

On Wed, Jan 13, 2016 at 05:44:16PM +0530, Saloni Jain wrote:
>  Hi Ben,
> 
> Thanks for the review.
> Regarding the test case, I want to clarify few points :
> 
>  # OFPT_TABLE_STATUS, OFPTR_VACANCY_UP
>     if test X"$1" = X"OFPTR_VACANCY_UP"; then shift;
>         ovs-vsctl -- --id=@t1 create Flow_Table flow-limit=10 -- set bridge br0 flow_tables:1=@t1
>         ovs-ofctl -O OpenFlow14 mod-table br0 1 vacancy:20,80
>         ovs-ofctl -O OpenFlow14 add-flow br0 table=1,in_port=1,actions=2
>         ovs-ofctl -O OpenFlow14 add-flow br0 table=1,in_port=2,actions=2
>         ovs-ofctl -O OpenFlow14 add-flow br0 table=1,in_port=3,actions=2
>         ovs-ofctl -O OpenFlow14 add-flow br0 table=1,in_port=4,actions=2
>         ovs-ofctl -O OpenFlow14 add-flow br0 table=1,in_port=5,actions=2
>         echo >>expout "OFPT_TABLE_STATUS (OF1.4): reason=VACANCY_UP
> table_desc:-
>   table 1:
>    eviction=off eviction_flags=OTHER|IMPORTANCE|LIFETIME
>    vacancy=on vacancy_down=20% vacancy_up=80% vacancy=10%"
>     fi
> 
> The above test case is for OFPT_TABLE_STATUS message. OFPT_TABLE_STATUS consists of table_desc also.
> As per the specification, if the switch sends OFPT_TABLE_STATUS with reason VACANCY_UP then further messages with VACANCY_UP reasons are stopped until VACANCY_DOWN reason comes.
> In the above test case, table limit is set to be 10 and 5 flows are added, also values of vacancy down and vacancy up are 20% and 80% respectively. 
> So in this case  OFPT_TABLE_STATUS (OF1.4): reason=VACANCY_UP is sent when first flow is added as in this case current Vacancy is 10% which is less than Vacancy down threshold value 20%. Further TABLE_STATUS messages are stopped until VACANCY_DOWN reason comes up which will occur when the current vacancy is greater than or equal to vacancy up threshold value 80%.

The misunderstanding here is the definition of "vacancy".  Vacancy is
the amount of free space, so when the first flow is added, the vacancy
is 90%, not 10%.
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