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

[medrees]

Dear Chris

      Thanks a lot for your reply, in cisco they by default allow 75% from
the configured bandwidth value under the interface, and it can be changed to
100% also it can support oversubscription by increasing the bandwidth value
under interface to value larger than the actual interface bandwidth (x2, x3
..)

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)

Thanks

Best Regards,
Mohamed Edrees

-----Original Message-----
From: Chris Kawchuk [mailto:juniperdude at gmail.com] 
Sent: Tuesday, September 13, 2011 11:02 AM
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? !!


1. RSVP reservations are just that - reservations. They don't actually
police/shape/take away available bandwidth on the interface for other
traffic.

LSPs ask for bandwidth reservations so that further/additional LSPs don't
attempt to book their bandwidth on this interface if it's full. (See
RSVP-TE)

2. Given no CoS on the LSP, and using the default JunOS Shapers; Network
Control traffic (Queue 3 or Queue 7 depending on your device) will always
have 5% of the available bandwidth/buffer space, regardless of the traffic
on the LSP. This is the Juniper default.

In other words, you can book the interface to 100% of line rate without
having to worry about network control traffic getting starved. In fact,
using the 'oversubscription' flag under RSVP, you can overbook the interface
as much as you want (i.e. 400% = Sell 4Gig of services down a single 1G
interface - and hope that all 4 LSPs don't try to use it at the same time).

I don't see the advantage in keeping 2.5 Gigabit/sec of bandwidth for
"control plane" traffic on a 10G link. =)

- Chris.


On 2011-09-13, at 3:42 PM, medrees wrote:

> Dear Experts
> 
> 
> 
>       I'm wondering from the default behavior of RSVP in Juniper 
> routers (By default, RSVP allows 100 percent the bandwidth for a class 
> type to be used for RSVP reservations.) while other vendors like Cisco 
> by default reserve only 75% and keeps 25% for the control plane 
> traffic (routing, L2 protocols messages..) giving them the highest 
> priorities (Priority 6, or 7) and that is logic.
> 
> 
> 
> so that what will juniper routers do for the control plane traffic if 
> the RSVP consumed the full 100% of the links?
> 
> 
> 
> Thanks in advance
> 
> 
> 
> Best Regards,
> 
> Mohamed Edrees
> 
> 
> 
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