[nsp] GSR engine types?

[Chris Whyte (GTS -- CONNECTIVITY SERV)]

A lot of the variability with the GSR, as with many products, is in how
packets are cellified (with extra overhead added) for transport across
the crossbar from LC to LC. It has much less to do with IFG as it does
with how efficiently the packet gets put into the fixed cell length in
which the GSR supports. In some cases you get lots of overhead and,
therefore, relatively poor overall throughput and in other cases you get
much better overall throughput. Clearly, the 4Mpps forwarding engine
creates an upper threshold. If I remember correctly, overall throughput,
depending on packet size mix and underlying L2 technology (eg GE vs
POS), throughput can vary from 2.4 to 3.1Gbps. This number also has a
tendency to change a bit depending of versions of IOS from my
experience.

Thanks,

Chris


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Rubens Kuhl Jr.
Sent: Monday, January 12, 2004 5:12 PM
To: Tom (UnitedLayer)
Cc: cisco-nsp at puck.nether.net
Subject: Re: [nsp] GSR engine types?


Engine 2 cards like 3-port Gig-E are not wire-speed at all packet sizes.
A
flood of small packets can't amount to 3 Gbps because of IFG (Inter
Frame
Gap) limitations, but at near 1.5Mpps from each Gig-E interface, the 4
Mpps
engine runs out of steam.

The 4-port SFP card that comes with Engine 3 presents the same design
choice. This doesn't mean the 2 extra ports are useless; if some
external
factor can limit the possible aggregate traffic, it's fine. Redundant
(active-standby, not active-active) connections usually presents such a
scenario.


Rubens


----- Original Message ----- 
From: "Tom (UnitedLayer)" <tom at unitedlayer.com>
To: "Rubens Kuhl Jr." <rubens at email.com>
Cc: <cisco-nsp at puck.nether.net>
Sent: Monday, January 12, 2004 8:39 PM
Subject: Re: [nsp] GSR engine types?


> On Sun, 11 Jan 2004, Rubens Kuhl Jr. wrote:
> > Too bad (if this document is complete) that so called "edge
features"
still
> > aren't available on 3-port GigE cards (with Engine 3, it could
support 2
> > GigE at wire speed), requiring one to buy a 10-port GigE card.
>
> So the 3 port GigE cards can't even do 3Gbps total?

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