From: Mike Bernico (mbernico@xxxxxxxxxxxx)
Date: Mon Sep 11 2000 - 19:22:00 GMT-3
Actually ABR is very much like non real time VBR. ABR does have one very
large advantage though. ABR uses closed loop feedback for control in the
form of VSVD (standard) or Foresight (cisco prop.) This allows it to burst
over MCR, up to PCR until foresight/vsvd detects congestion. VBR only
allows you to burst past MCR for a certain number of cells. If you had an
ATM network with PVCs connecting your data centers/POPs together ABR would
be the way to go. Unfortunately on StrataCom equipment ABR and UBR share
the same queue.
-----Original Message-----
From: Earl Aboytes [mailto:earl@linkline.com]
Sent: Monday, September 11, 2000 3:56 PM
To: shotcaller30; Scott F. Robohn
Cc: cciemail
Subject: Re: ubr+ vs. abr
> ----------
> From: Earl Aboytes[SMTP:EARL@LINKLINE.COM]
> Sent: Monday, September 11, 2000 3:55:38 PM
> To: shotcaller30; Scott F. Robohn
> Cc: cciemail
> Subject: Re: ubr+ vs. abr
> Auto forwarded by a Rule
>
UBR is a best effort service class that holds no guarantees. It has the
lowest priority of all the services.
ABR is a low priority service but not as low as ubr. It allows for the
specification for a minimum cell rate (mcr) which is not provided for in
ubr. UBR+ does allow for an MCR so the only difference becomes the
priority.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Earl Aboytes CCIE #6097
Senior Technical Consultant
Verizon Managed Solutions
805-381-8817
earl.aboytes@verizon.com
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
---------- Original Message ----------------------------------
From: "Scott F. Robohn" <sfr@mentortech.com>
Reply-To: "Scott F. Robohn" <sfr@mentortech.com>
Date: Mon, 11 Sep 2000 16:22:28 -0400
>Not quite sure about this, but I think UBR+ was a Cisco
>marketing-type phrase for an ABR-like traffic management
>category before ABR actually existed.
>
>FWIW,
>sfr
>
>> shotcaller30 wrote:
>>
>> I'm having trouble figuring out the difference between abr
>> and ubr+.
>>
>> The docs show this for ABR
>> In ABR transmission, the peak cell rate (PCR) specifies
>> the maximum value of the allowed cell rate (ACR), and
>> minimum cell rate (MCR) specifies the minimum
>> value for the ACR. ACR varies between the MCR and the PCR
>> and is dynamically controlled using congestion control
>> mechanisms.
>>
>> and this for ubr+
>> To select Unspecified Bit Rate (UBR) QOS and configure the
>> output peak cell rate and output minimum guaranteed cell
>> rate for an ATM PVC, SVC, or VC class,
>> use the ubr+ command in the appropriate command mode.
>
>--
>>> Scott F. Robohn, CCSI #20826/CCNP/CCDP ........ 703-623-3752 <<
>>> mentor technologies ..... Service Provider Engineering Group <<
>>> mailto:sfr@mentortech.com ........ http://www.mentortech.com <<
>>> ........... Formerly Chesapeake Network Solutions .......... <<
>
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