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RE: [RPRWG] MAC Question




I agree with Harry although at the appropriate link speeds, the difference
between store-and-forward and cut-through is not material.
 
 
Kevin

-----Original Message-----
From: Harry Peng [mailto:hpeng@xxxxxxxxxxxxxxxxxx]
Sent: Thursday, March 22, 2001 7:37 AM
To: stds-802-17@xxxxxxxx
Subject: RE: [RPRWG] MAC Question



All: 

On the ring, whether a packet is store and forward or cut through does
affect the delay/jitter 
performance. Especially the ring is a frame based with variable frame size.
The transit path is 
also the shared medium so it affects every packet in flight. 

I beg to differ that it is a trade-off between the ingress path or the
transit path. 

Regards, 


Harry 


-----Original Message----- 
From: Steven Wood [ mailto:swood@xxxxxxxxx <mailto:swood@xxxxxxxxx> ] 
Sent: Thursday, March 22, 2001 10:05 AM 
To: Ray Zeisz 
Cc: stds-802-17@xxxxxxxx 
Subject: Re: [RPRWG] MAC Question 



Ray, 

This is a design choice and is currently the subject of much 
debate within RPR.  My view is that the latency/jitter issues 
will be there in either a store & fwd or cut-through design. 

It is simply a question of where you introduce the jitter, 
on the ingress path or the transit path. 

In the next couple of meetings, I'm sure we will be seeing 
some concrete results to compare the two approaches. 

At 09:02 AM 3/22/01 , Ray Zeisz wrote: 
> 
>I am following the .17 group from afar, but I have a question: 
> 
>Is it acceptable for each node in the ring to buffer up an entire packet 
>before forwarding it to its neighbor?  Would the latency be to great if
this 
>were done?  Or is the .17 direction more along the lines of 802.5 where
only 
>a few bits in each ring node are buffered...just enough to detect a token 
>and set a bit to claim it. 
> 
>Ray 
> 
>Ray Zeisz 
>Technology Advisor 
>LVL7 Systems 
> http://www.LVL7.com <http://www.LVL7.com>  
>(919) 865-2735 
> 
> 

Steven Wood, 
Manager, Hardware Engineering 

Cisco Systems Co.                      
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