Subject: RE: setting ER-LSPs

From: [email-masked]
Date: Fri, 28 Jan 2000 15:46:27 -0500

Panos Trimintzios wrote:
> As far as I have read about the ER-LSPs they reflect 
> the administrator's decisions/policies (right?) in 
> order (not only) to do TE.
> If that is true then could someone use a management
> protocol (eg. SNMP) to set an ER-LSP?

Yes, one could use SNMP to configure the ERLSP. Please see
http://www.ietf.org/internet-drafts/draft-ietf-mpls-te-mib-01.txt
and
http://www.ietf.org/internet-drafts/draft-ietf-mpls-lsr-mib-00.txt
for more details.

> If yes why do we prefer signalling (CR-LDP or extendent RSVP),
> If not why?

Even if you have decided on the path through the network, it
is easier to talk to the LSR at one end of the ERLSP (via
SNMP) and instruct it to set up the ERLSP via LDP/RSVP than
to talk SNMP to each switch along the path. BTW, the above
MIBs allow you to take both approaches.

Cheenu

---

From: Panos Trimintzios <[email-masked]>
Date: Fri, 28 Jan 2000 21:36:56 +0000 (GMT)

Hi again,

> MIBs allow you to take both approaches.

1. Why it is "easier" to talk to one end of ER-LSP (via SNMP)
   and then signal the setup, since the signaling requires
   (for both CR-LDP and ext-RSVP) to go all the way to the other 
   end of the ER-LSP and then back to where it began, and 
   possibly again notify (via SNMP) the administrator process.
   Is there any work that has been done to test this? 
   Isn't more complicated to use [SNMP + (LDPorRSVP)] than to
   use only [SNMP]?

2. Someone could argue against the above by giving details 
   about the "weaknesses" of SNMP (eg not suitable for real-time
   operations, unreliability(UDP) etc). Comming  back to 
   my original question we can see that I have asked if we
   could use a management protocol, not necessarily SNMP,
   but another more suitable, lets say XXXP (one example that 
   comes to my mind is COPS-PR).
   So I repeat my argument/questions in 1. , by replacing SNMP 
   with XXXP.

Regards,

Panos Trimintzios
Centre for Communication
Systems Research 
University of Surrey, UK

---

From: Petri Aukia <[email-masked]>
Date: Fri, 28 Jan 2000 17:02:49 -0500

>   and then signal the setup

   Some of the key issues for arguing for actual network protocols
   instead of just centralized control are 

   a) Atomicity. In controlling the network from the core it is
      not as obvious how to create a path in a way that is robust
      against different network and device failures. It is easy to
      see that a trivial implementation could leave the network in
      an unsuitable state, given one of many modalities of failure.

   b) The edge initiated protocols are naturally suitable for different
      configurations of control, not only directed from the core, but
      just as well initiated by the edge, a regional mid-level entity, 
      a protective local configuration in case of core failure, etc.
      For the alternative approaches, such as the regionalized control 
      the edge initiation seems to provide a cleaner trust model.

>   about the "weaknesses" of SNMP 

   Someone could, and not without merit.

Peba
-- 
Petri Aukia                               Room 4c-504 Lucent Technologies  
Tel: (732) 949 3697                       101 Crawfords Corner Road, 
Fax: (732) 834 5379                       Holmdel NJ  07733
email: [email-masked]