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Versions: 00 01 Draft is active
In: IS-review
INTERNET-DRAFT                     Haresh Khandelwal & Sushrut Deshpande
Intended Status: Experimental                              Cisco systems
Expires:                                                   February 2012


     MIB Classification based use of SNMP cache or shared database
               draft-haresh-sushrut-mib-classification-00


Abstract

   This memo defines classification of MIBs to use SNMP cache or shared
   database mechanism to reduce high CPU usage while SNMP MIBs are
   polled or GET operations performed from MIB browser.


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
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   The list of current Internet-Drafts can be accessed at
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Copyright and License Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors. All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document. Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document. Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.



Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1  Terminology . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  MIB classification . . . . . . . . . . . . . . . . . . . . . .  3
     2.1 MIB Classification . . . . . . . . . . . . . . . . . . . . .  3
     2.2 SNMP Cache and Shared database . . . . . . . . . . . . . . .  3
   3  Security Considerations . . . . . . . . . . . . . . . . . . . .  5
   4  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  5
   5  References  . . . . . . . . . . . . . . . . . . . . . . . . . .  5
     5.1  Normative References  . . . . . . . . . . . . . . . . . . .  5
     5.2  Informative References  . . . . . . . . . . . . . . . . . .  5
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  5
































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1  Introduction

   Continuous SNMP polling or GET operations on managed device results
   into high CPU usage. This is due to high process interactions between
   SNMP and requested OID's process. This draft suggests way to reduce
   process interactions in order to reduce CPU usage.

1.1  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].


2.  MIB classification

   When SNMP PDUs are received by SNMP on managed device (router, switch
   etc...), SNMP will look into ODI and fetch its value either from
   cache table or shared data base based on its MIB category.

2.1 MIB Classification

       i) Dynamic MIBs - Whose values change frequently (for example
   ifMIB counters). Value of object falls under this MIB category will
   be fetched from shared Database by SNMP

       ii) Relatively Static MIBs - Whose values change occasionally
   (for example VLAN MIB). Value of object falls under this MIB category
   will be fetched from SNMP cache table

2.2 SNMP Cache and Shared database

   In case of shared database, component or process who falls under
   "Dynamic MIBs" have to populate SDB (shared database) for SNMP. This
   particular process is completely responsible for those SDB table
   values. So, if it is ifMIB counter process for interface then it will
   be responsible for interfaces counters value in SDB. SNMP will pickup
   relevant values for asked OIDs from SDB and will send it to MIB
   browser.

   In case of SNMP Caching Mechanism, component or process who falls
   under "Relatively Static MIBs", SNMP will interact with those
   processes when OID requested 1st time and SNMP will form its own
   cache table which in turn, stores values of all processed ODIs. So
   when next time same OID will be requested, SNMP can response from its
   own Cache table. Here, if value of OID from "Relatively Static MIBs"
   changes, that process or component has to inform SNMP regarding its
   event and new values. This is similar to internal trap



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   communications. SNMP will accordingly update its Cache table.

   SNMP cache table can be flushed in event of SNMP
   restart/crash/enable-disable. Cache table will be formed again after
   recovery with 1st poll cycle.

   shared database will be handled by individual process and should be
   populated again in event of process crash/restart. This way, we can
   reduce interaction messages between SNMP and other processes and so
   does CPU usage.









































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3  Security Considerations

   This design is not changing SNMP packets. It does not apply on SNMP
   SET operation. Communication between SNMP manager and agent is also
   un changed, only internal process interaction changes are proposed
   based on MIB classification in network managed device. so, this
   design does not exhibit any security threat.


4  IANA Considerations


5  References

5.1  Normative References



5.2  Informative References




Authors' Addresses


   Name
   Haresh Khandelwal
   Sushrut Deshpande

   EMail: hkhandel@cisco.com, susdeshp@cisco.com




















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