Subject: [Sigtran] SCTP MIB

From: Eiband Ernst <[email-masked]>
Date: Fri, 8 Mar 2002 15:18:07 +0100

Hi,

I have some proposals for updating the SCTP MIB:

(1) sctpAssocId

    This object has the following DESCRIPTION clause:

       "Association Identification. Value identifying the association
       (typically the Initiate Verification Tag).

        Value zero is reserved to indicate no association."

    The verification tag is usually a random value which is not
    necessarily unique. In many SCTP implementations the verification
    tag cannot be used to identify an association. Therefore, I suggest
    to delete the remark in brackets. It is a matter of implementation
    which values are provided as association identifiers.

    I think the meaning of value zero should be clarified, e.g.
       "Value zero is not allowed, it may be used in other MIBs to
        indicate no association."

    Additionally, the SYNTAX of sctpAssocId should be changed to
       Unsigned32(1..4294967295)
    to exclude index 0.

(2) Statistics

    The statistics objects sctpAssocT1expireds, sctpAssocT2expireds,
    and sctpAssocRtxChunks should be moved to the sctpStatGroup.

    It might be useful to have global as well association specific
    statistics counters (the TCP MIB has only global counters). In
    many systems SCTP associations may be active for a long period
    of time, e.g. when used for signalling purposes. Furthermore, an
    association entry may exist in the MIB even if the association
    is not active (sctpAssocState set to closed). In both cases
    association specific counters make sense. Therefore, I suggest
    to modify the SCTP MIB as described below.

    Add the following global statistics counters:
     - sctpT1expireds
     - sctpT2expireds
     - sctpRtxChunks

    Include a new table for association specific statistics
    (sctpAssocStatsTable) containing the following objects:
     - sctpAssocOutCtrlChunks
     - sctpAssocOutOrderChunks
     - sctpAssocOutUnorderChunks
     - sctpAssocInCtrlChunks
     - sctpAssocInOrderChunks
     - sctpAssocInUnorderChunks
     - sctpAssocFragUsrMsgs
     - sctpAssocReasmUsrMsgs
     - sctpAssocOutSCTPPacks
     - sctpAssocInSCTPPacks
     - sctpAssocT1expireds
     - sctpAssocT2expireds
     - sctpAssocRtxChunks

    The remote address table contains only one statistics counter,
    sctpAssocRemAddressRtx. Other counters are also path specific,
    e.g. OutOrderChunks and OutUnorderChunks. However, I don't
    think that it is worth to count chunks and packets separately
    for every path. In my opinion, sctpAssocRemAddressRtx should be
    removed.

    As the statistics group is optional, some implementations may
    support both global and association specific statistics, others
    may support only one set of counters.

Best regards,
E. Eiband

---

From: Juergen Schoenwaelder <[email-masked]>
Date: Fri, 8 Mar 2002 16:01:26 +0100

>>>>> Eiband Ernst writes:

Eiband> I have some proposals for updating the SCTP MIB:

Eiband> (1) sctpAssocId

Eiband>     This object has the following DESCRIPTION clause:

Eiband>        "Association Identification. Value identifying the
Eiband> association (typically the Initiate Verification Tag).

Eiband>         Value zero is reserved to indicate no association."

Eiband>     The verification tag is usually a random value which is
Eiband> not necessarily unique. In many SCTP implementations the
Eiband> verification tag cannot be used to identify an
Eiband> association. Therefore, I suggest to delete the remark in
Eiband> brackets. It is a matter of implementation which values are
Eiband> provided as association identifiers.

Eiband>     I think the meaning of value zero should be clarified,
Eiband> e.g.  "Value zero is not allowed, it may be used in other MIBs
Eiband> to indicate no association."

Eiband>     Additionally, the SYNTAX of sctpAssocId should be changed
Eiband> to Unsigned32(1..4294967295) to exclude index 0.

Perhaps it is worth to introduce two TCs to capture the semantics and
to allow other MIB modules to refer to SCTP associations (1:1 or
1:0-1):

SctpAssocIndex ::= TEXTUAL-CONVENTION
    STATUS	curent
    DESCRIPTION
	"A unique value, greater than zero, which identifies an 
	 SCTP association."
    SYNTAX	Unsigned32(1..4294967295)

SctpAssocIndexOrZero ::= TEXTUAL-CONVENTION
    STATUS	current
    DESCRIPTION
        "This textual convention is an extension of the SctpAssocIndex
	 convention. This extension permits the additional value of
         zero. The value zero is object-specific and must therefore be
         defined as part of the description of any object which uses
         this syntax."
    SYNTAX	Unsigned32

This follows IF-MIB and ENTITY-MIB experiences where things over time
went into this direction.

/js

-- 
Juergen Schoenwaelder    <http://www.informatik.uni-osnabrueck.de/schoenw/>

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