Subject: [Diffserv] mib 14

From: Ronen Tausi <[email-masked]>
Date: Thu, 11 Oct 2001 17:43:14 +0200

hello

i have 2 question regarding the draft of mib 14 :

1. in the mib in regard to row pointer it states that if we try to config a
row pointer that does not point to a valid entry we must return
inconsistentvalue error , but if config
 a valid rowpointer and than that entry becomes non valid we simply treat it
as if it has zero dot zero value,
 if we save configuration ( snap ) and try to use it to reconfigure the
device we will get inconssitent value because the entry is non valid , is
that aa acceptable situation ?

2. in the action table the interface field was added that hold the if index
but it states that the ifindex can be derived from the datapath and
following the row pointer,  
  what if the interface is not one of the data path ifindex ? .
 if we have multiple data path that point to the same action , how can we
determine the right value ? , and if we five the interface the value 0 ,
will that mean we can use 
all the derived ifindexs ?

thanks 

gain

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From: Harrie Hazewinkel <[email-masked]>
Date: Thu, 11 Oct 2001 11:26:04 -0700

> that aa acceptable situation ?

I am not sure if I get this. I try to explain.

When you want to configure a RowPointer you need to create the row to
which it points before. Otherwise you get the 'inconsistentvalue' returned.

If later the configuration is changed and the row to which the RowPointer
pointed is deleted the RowPointer will be treated as if it were '0.0'.

However, if you want to have the same RowPointer used later you cannot.
That row to which it pointed is deleted (not avaialble) and thus you have
the same  situation as in the very first use of the RowPointer pointing to a
non-existant row.

Is this what you are asking??

> what if the interface is not one of the data path ifindex ? .

In that case the value is indeterminate. The agent cannot determine
the 'single' ifIndex the action belongs to. Thus, indeterminate and the
value is '0' (as specified in the description clause).

> determine the right value ? ,

> and if we five the interface the value 0 ,

If the action is from a datapath that merges from 5 interfaces the
management application can make note of it. If the management application
builds its own internal structures for the datapath representations.

Harrie

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From: Juergen Schoenwaelder <[email-masked]>
Date: Fri, 12 Oct 2001 12:54:08 +0200

>>>>> Ronen Tausi writes:

Ronen> 1. in the mib in regard to row pointer it states that if we try
Ronen> to config a row pointer that does not point to a valid entry we
Ronen> must return inconsistentvalue error , but if config a valid
Ronen> rowpointer and than that entry becomes non valid we simply
Ronen> treat it as if it has zero dot zero value, if we save
Ronen> configuration ( snap ) and try to use it to reconfigure the
Ronen> device we will get inconssitent value because the entry is non
Ronen> valid , is that aa acceptable situation ?

I think the text implies that an application which read the DiffServ
MIB and later tries to restore it via a sequence of SNMP set
operations must be able to detect and handle dangling pointers. Note
also that such an application has to be smart enough to create the
rows in the right order.

I expect that this is actually not too hard to do - but since I have
not coded this myself yet, surprises might be possible. ;-)

BTW, the PIB puts even stronger requirements on the PDP. The PIB
requires that number of rows is kind of minimal (see the UNIQUENESS
clauses in the DiffServ PIB).

/js