RE: COPS vs. SNMP

["Durham, David" <david.durham@intel.com>]

Hi Tricha,

I think I forgot to address your second question. Yes, resource reservation
in a network can be achieved via COPS. Its primary advantage over SNMP is
that it was designed with this specific purpose in mind. Specifically:

* COPS-PR supports a completely transactional model:
	o Messages represent atomic transactions. 
	o All parts of a transaction either succeed or fail.
	o On failure, the device automatically rolls-back to its last
operational state.
	o The server can also quickly switch between provisioned contexts
(eg. from day policies to night policies).
	o Failures and errors are very precisely reported PEP to PDP.
	o Supports large transactions.
	o Implementations do not worry about caching random attributes
waiting for a complete transaction (as is a problem for SNMP), everything in
the transaction comes at once in one message.
* COPS-PR supports structured row-level access:
	o A row represents an atomic unit for data communication.
	o There is no need for rowstatus, owner strings and the like.
	o A row is essentially an indivisible structured data type.
	o OID data is sent only once per row, representing a 10x gain in
on-the-wire efficiency over SNMP for e.g. a packet classifier filter w/ 10
fields.
* COPS-PR supports multi-manager control without the danger of corruption:
	o Each PDP has its own data instance space on the PEP which cannot
be manipulated by other PDPs.
	o PDPs data instances are isolated by the message-level client-type
field.
* Completely event-driven:
	o There is no polling in COPS-PR. 
	o PEPs notify PDPs only when there is something to report and vice
versa.
	o Persistent TCP connection means no 3-way handshake overhead for
messages.
	o TCP heartbeat verifies aggregate communication over the connection
and confirms operational status.
* Multiple Levels of security:
	o COPS intrinsically provides message-level integrity with PEP and
PDP authentication.
	o COPS over TLS provides additional level of authentication and
private communication.
	o IPSec provides yet another level of authentication and privacy. 
	o ... All communication is secure before the first COPS-PR message
is even exchanged. 	
* Object-Oriented Data Model and Data Definition Language.
	o COPS-PR via the SPPI improves the state of the art over the SNMP
SMI.
		- Allows inheritance of data structures.
		- Allows typed references.
		- Allows structured containment.
		- Allows typed associations.
		- Allows typed groupings.
		- Adds support for Integer64 and other basic data types.
		- Maximizes reuse of data definitions.
	o Via the framework PIB provides a data model that can be
reused/shared across PIBs for common/redundant policy functions and
definitions.
	o All new PIB definitions can integrate with existing PIB
definitions to add features and capabilities.
	o Common data-path theme throughout COPS-PR PIBs.
* Capabilities Reporting:
	o COPS-PR via the framework PIB provides a mechanism by which the
PEP clearly yet generically describes what PIBs and parts of PIBs it
supports.
	o Both semantic and syntactic capabilities are generically
communicated PEP to PDP.
* COPS-PR integrates event outsourcing and provisioning:
	o Eg. when an RSVP message is signaled & outsourced PEP-PDP, a
diffserv provisioning policy can be pushed down.
	o Integrated provisioning and outsourcing can be accomplished over
one message RTT.
	o Policy usage information can be used to signal a policy change.
* COPS provides built-in synchronization and failover:
	o PEP automatically moves to backup PDPs on failure.
	o PDP quickly synchronizes state with PEP after communication
failure.
		- Quick last transaction ID verifies PEP state.
		- PDP can resynchronize all or any selected state.
	o Enables quick TCP session recovery.
* COPS-PR inherently was designed to run over reliable transport via TCP.


Well, anyway, these are some of the main reasons for COPS-PR that come to my
mind.

Cheers,
-Dave



> -----Original Message-----
> From: Tricha Anjali [mailto:tricha@ece.gatech.edu]
> Sent: Monday, February 25, 2002 9:38 AM
> To: rap@ops.ietf.org
> Cc: Ian F. Akyildiz
> Subject: COPS vs. SNMP
> 
> 
> 
> Hello,
> 
> We have been following the IETF activities concerning the 
> ongoing work in
> the fields of SNMP and COPS. It seems that at the meeting in 
> March 2000 in
> Adelaide, the snmpconf working group was formed for issues 
> dealing with
> policy-based network management after the BOF about network 
> management in
> Dec 1999. However, now the group seems to have accomplished 
> its charter
> and finished. Does this mean that the discussion has been resolved?
> 
> We would like to know if the resource reservation in a 
> network can/should
> be achieved via COPS? If yes, how is it advantageous over SNMP?
> 
> Any help will be appreciated!
> 
> Thanks in advance,
> 
> Tricha
> 
> -------------------------------
> Tricha Anjali
> Broadband & Wireless Networking Lab
> School of Electrical and Computer Engineering
> Georgia Institute of Technology
> http://users.ece.gatech.edu/~tricha/
> 
> 
> 
>