From: Brian McGahan (bmcgahan@internetworkexpert.com)
Date: Wed May 25 2005 - 14:08:26 GMT-3
<cco>
Queueing on the transmit ring introduces a serialization delay that is
directly proportional to the depth of the ring. An excessive
serialization delay can impact latency budgets for delay-sensitive
applications such as voice. Thus, Cisco recommends reducing the size of
the transmit ring for VCs carrying voice. Select a value based on the
amount of amount of serialization delay, expressed in seconds,
introduced by the transmit ring. Use the following formula:
((P*8)*D)/S
P = Packet size in bytes. Multiply by eight to convert to bits.
D = Transmit-ring depth.
S = Speed of the VC in bps.
</cco>
http://www.cisco.com/warp/public/121/txringlimit_6142.html#topic6
HTH,
Brian McGahan, CCIE #8593
bmcgahan@internetworkexpert.com
Internetwork Expert, Inc.
http://www.InternetworkExpert.com
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> -----Original Message-----
> From: Andrew Lee Lissitz [mailto:alissitz@corvil.com]
> Sent: Wednesday, May 25, 2005 12:04 PM
> To: Brian McGahan; ccielab@groupstudy.com
> Cc: 'Mark Lasarko'
> Subject: RE: tx-?-limit
>
> For my question to the group; is there a doc that outlines and
answers:
>
> * For links with mostly Voice and small packets, with X speed,
configure
> the
> tx-ring to be X
> * For links with mostly IMIX, with X speed, configure the tx-ring to
be X
>
> Is there something simple out there or does one need to perform the
> calculations? Kindest regards all,
>
> Andrew Lee Lissitz
> 908.303.4762
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Brian McGahan
> Sent: Wednesday, May 25, 2005 12:07 PM
> To: ccielab@groupstudy.com
> Cc: Mark Lasarko
> Subject: RE: tx-?-limit
>
> Hi Mark,
>
> The TxR is the transmit ring of the interface. This is the
> hardware queue, and the last stop for a packet before it is
encapsulated
> on the interface. The size of the TxR will ultimately affect the
> serialization delay on the interface. This value would typically only
> needed to be modified if you have specific low latency requirements
out
> an interface.
>
> If you really want more information on this subject pick up the
> book "Inside Cisco IOS Software Architecture" from Cisco Press. Also
> don't be fooled by the size of the book, it is by far the most in
depth
> book published by Cisco Press ;)
>
> HTH,
>
> Brian McGahan, CCIE #8593
> bmcgahan@internetworkexpert.com
>
> Internetwork Expert, Inc.
> http://www.InternetworkExpert.com
> Toll Free: 877-224-8987 x 705
> Outside US: 775-826-4344 x 705
> 24/7 Support: http://forum.internetworkexpert.com
> Live Chat: http://www.internetworkexpert.com/chat/
>
>
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of
> > Mark Lasarko
> > Sent: Wednesday, May 25, 2005 10:51 AM
> > To: <Andrew Lee Lissitz; ccielab@groupstudy.com;
> Andrew.Diment@qwest.com
> > Subject: RE: tx-?-limit
> >
> > Greetings Andrew & Andy, respectively
> >
> > Unfortunately, the link offered was one of those that was not
helpful
> to
> > me.
> > Per my initial post, I already read all the ATM-PA stuff.
> >
> > My questions are:
> >
> > 1) Why is the tx-queue-limit command automagically added?
> > (translation: when you issue tx-ring-limit this phantom command
> > appears)
> >
> > 2) Why is the tx-queue-limit command unavailable directly?
> > (translation: it's not there in the command line)
> >
> > 3) What exactly do these commands do on non-PA interfaces?
> > (translation: I am a little slow and I still don't get it)
> >
> > Thanx!
> > ~M
> >
> > >>> "Diment, Andrew" <Andrew.Diment@qwest.com> 05/25/05 11:37 AM >>>
> >
> > I helps tweak QoS.
> >
> >
>
http://www.cisco.com/en/US/tech/tk39/tk824/technologies_tech_note09186a0
> 08
> > 00f
> > bafc.shtml
> >
> > Andy
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf
Of
> > Mark Lasarko
> > Sent: Wednesday, May 25, 2005 10:28 AM
> > To: 'GroupStudy'
> > Subject: tx-?-limit
> >
> >
> > Looking for other ways to tweak interfaces:
> >
> > Rack1R1(config-if)#tx?
> > tx-ring-limit
> > Rack1R1(config-if)#tx-ring-limit 123
> > Rack1R1(config-if)#end
> > Rack1R1#sh run | b interface Serial0/0
> > interface Serial0/0
> > no ip address
> > encapsulation frame-relay
> > tx-ring-limit 123
> > tx-queue-limit 123
> >
> > (note: tx-queue-limit is automagically added to the config)
> >
> > I tried looking this up only to find some ATM-PA references that did
> not
> > clarify.
> > ...Same commands (or lack thereof) appear to be true/available on
> > ethernet,
> > etc...
> > I hope am clear in thinking this has nothing to do with the
hold-queue
> in
> > |
> > out command
> > (which defines the maximum # of input and output queues as I
> understand
> > it)
> >
> > That said, I am curious just what this does, if anything
> > And why we cannot do just a queue-limit?
> > (since that command does not exist??)
> >
> > ~M
> >
> >
>
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