Subject: [Isis-wg] help needed for issues related to certain ISIS Mib Objects

From: "Dan Ye \(daye\)" <[email-masked]>
Date: Tue, 27 Feb 2007 10:30:36 -0800

Hi All:
   I'm a developer working on ISIS and  I found some problems when
implementing certain ISIS MIB objects. The definition for
ciiSysPollESHelloRate is as follows:
   ciiSysPollESHelloRate OBJECT-TYPE
        SYNTAX CiiUnsigned16TC (1..65535)
        UNITS "seconds"
        MAX-ACCESS read-write
        STATUS current
        DESCRIPTION
            "The value, in seconds, to be used for the suggested ES
             configuration timer in ISH PDUs when soliciting the ES
             configuration."
        REFERENCE "{ISIS.aoi pollESHelloRate (13)}"
        DEFVAL { 50 }
    ::= { ciiSysObject 6 }

The valid range for ciiSysPollESHelloRate is defined as 1..65535.
However, by default, this timer is disabled and no timer tlv is inserted
into the hello packet. I wonder if the valid range for
ciiSysPollESHelloRate shall be changed to 0..65535 and 0 means this
timer option is disabled. If we keep valid range as 1..65535, then we
may need another field to indicate whether this timer option is disabled
or not. Various vendor implementations disable this timer option by
default and no timer tlv is inserted into hello packet. If we return a
default value of 50 when this timer option is in fact disabled, it can
be somewhat misleading to customers. But if we return a value of 0, the
snmp agent reports out-of-range value because 0 is not considered a
valid value for ciiSysPollESHelloRate. Your comments about how to
resolve this issue is welcome.
 
Another issue is related to CiiSysLevelMinLSPGenInt. Current definition
of this object is as follows:
isisSysLevelMinLSPGenInt OBJECT-TYPE
        SYNTAX Unsigned16TC (1..65535)
        UNITS "seconds"
        MAX-ACCESS read-create
        STATUS current
        DESCRIPTION
            "Minimum interval, in seconds, between successive generation
             of LSPs with the same LSPID at this level by this instance
             of the protocol.  This object follows the resettingTimer
             behavior."
        REFERENCE "{ISIS.aoi minimumLSPGenerationInterval (11)}"
        DEFVAL { 30 }
    ::= { isisSysLevelEntry 3 }

The unit for CiiSysLevelMinLSPGenInt is seconds.  Various
implementations use milliseconds instead of seconds as units for
CiiSysLevelMinLSPGenInt  to support fast convergence.  However, current
mib uses seconds as units, then we have to round up to 1 seconds if the
value configured is less than 1 second. Will you consider change the
UNITS from seconds to milliseconds in the future as the demand for
faster convergence in the network requires sub-second timing precision?
 
Your input regarding to the above issues of ISIS MIB definition will be
greatly appreciated.
 
Thanks
 
Dan Ye 
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---

From: "Parker, Jeff" <[email-masked]>
Date: Tue, 27 Feb 2007 16:57:24 -0500

Dan 
     I read this to be controlling how often an IS regenerates an LSPs describing itself. 
State may be changing quickly on a router, but excess generation of new LSPs would lead to thrashing.  A bit of hysteresis will help fast convergence.  

- jeff parker

 
 
Thanks
 
Dan Ye