[j-nsp] RSVP reserve 100% of interface BW in Juniper while 75% in Cisco? !!

[medrees]

Dear Chris 

  Thanks a lot for your clear and professional support.

Best Regards,
Mohamed Edrees

-----Original Message-----
From: Chris Kawchuk [mailto:juniperdude at gmail.com] 
Sent: Tuesday, September 13, 2011 6:46 PM
To: medrees
Cc: juniper-nsp at puck.nether.net
Subject: Re: [j-nsp] RSVP reserve 100% of interface BW in Juniper while 75%
in Cisco? !!

> Please clarify more this statement (have 5% of the available 
> bandwidth/buffer space) as I understood if the interface is completely 
> utilized using LSP traffic the buffer will be utilized and may 
> starving the control traffic (please correct me)


You need to understand the difference between an RSVP bandwidth booking, and
a CoS Queue.
JunOS always has 2 forwarding classes (and hence HW queues) per interface as
a default.

JunOS CoS Queue defaults:
	Network Control - High Priority - 5%
	Everything Else - Low Priority  - 95% (i.e. Your LSP)

In your case - the best-effort queue buffer will be fully utilized.

When traffic is queued for egress on an interface, the default schedulers
always service the Network control traffic first, regardless of your RSVP
LSP size, or how busy it is. An Interface "completely utilized using LSP
traffic", will always be able to send network control traffic. 

A low priority CoS Queue (The RSVP LSP) cannot starve a High Priority CoS
Queue (Network Control Traffic).

- Chris.