Re: [RPRWG] MAC Question
Harry,
with my Cisco Hat on,
I beg to differ with you, the jitter difference between
store and forward and cut-through (my definition is partial
store and foward, i.e. cut-through if not injecting a packet, storing
transit data while injecting (no segmentation) is not
as significant as the jitter introduced by the queueing
mechanisms at the ingress point.
But this smells more like good fodder for presentations
at the next meeting.
mike
> Harry Peng wrote:
>
> 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]
> 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
> >(919) 865-2735
> >
> >
>
> Steven Wood,
> Manager, Hardware Engineering
>
> Cisco Systems Co.
> 365 March Rd.
> Kanata, Ontario
> CANADA K2K 2C9 | |
> Phn: (613) 271-3450 :|: :|:
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> http://www.cisco.com C i s c o S y s t e m s
--
Michael Takefman tak@xxxxxxxxx
Manager HW Engineering, Cisco Systems
Chair IEEE 802.17 Stds WG
2000 Innovation Dr, Ottawa, Canada, K2K 3E8
voice: 613-271-3399 fax: 613-271-4867