From: Scott Morris (smorris@ipexpert.com)
Date: Mon Feb 25 2008 - 12:39:56 ARST
Are we talking about real life here, or the lab?
In real life, I would assume that the math I'm making the router to has
something to do with real packets and real ratios, so I'd suggest the 1536.
In the lab, I honestly don't think anyone really cares about that 8k
difference from the Cisco default of 1544 to the realistic usable amount of
1536.
Watch the lab for any wording to the contrary, but if nothing is asked, I'd
leave well enough alone. Better to not mess with anything you weren't
expected to mess with!
HTH,
Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, JNCIE-M
#153, JNCIS-ER, CISSP, et al.
CCSI/JNCI-M/JNCI-ER
VP - Technical Training - IPexpert, Inc.
IPexpert Sr. Technical Instructor
A Cisco Learning Partner - We Accept Learning Credits!
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-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of Greg
Wendel
Sent: Sunday, February 24, 2008 1:05 PM
To: mgreenlee@ipexpert.com
Cc: Todd, Douglas M.; Radioactive Frog; Cisco certification; ccie forum
Subject: Re: Frame-relay trafic shaping
Marvin,
Thanks for the good info. Could you tell me your opinion on whether to use
int serial x/x
bandwidth 1536
or
int serial x/x
bandwidth 1544
when asked to specify T1 speeds on a QOS task?
Thanks,
On Fri, Feb 22, 2008 at 9:38 PM, <mgreenlee@ipexpert.com> wrote:
> Slight correction
>
> 1. Applying QoS to a circuit doesn't "take" 75% of the bandwidth.
>
> The limitation of the max-reserved is to prevent someone from applying
> a policy that is asking for a value higher than the max-reserved
> value. The max-reserved value only affects whether or not your policy
> can be applied to the interface, it doesn't affect the calculation.
>
> So if you have a policy asking for 20%, and someone set your max
> reserved to 30%, the 30% is not used in the calculation, and only
> comes into play if your policy was asking for more than 30%, in which
> case, the router gives you a nice message, and doesn't take the
> command when you try to apply the policy to the interface.
>
> (Also, to be specific, bandwidth is reserved in policy-map statements,
> not class-map statements)
>
> The value could be from CIR, or it could be from line rate, I would
> expect them to tell you in the question.
>
> As mentioned before, make sure that your interface bandwidth matches
> the bandwidth of the circuit. With a serial line default of 1544, if
> the actual circuit is only 128k, then a reservation of 10% can
> overwhelm the circuit, as the router "thinks" that 154k is 10%
>
> However, the answer also is "it depends". There were some IOS
> versions between 12.1t and 12.2 / 12.2T where they changed things
> around a bit, and some versions actually did the calculations based on the
'max-reserved'
> value, so asking for 20% with max-reserved set to 75% would really
> allocate 15%. So if you're on a device with an older IOS version, the
> results may vary a bit from what the newer code will do. Make sure to
> take a close look at your show commands - show policy-map int, etc. to
> see what the router is telling you.
>
>
>
>
>
>
>
>
>
> Marvin Greenlee, CCIE #12237 (R&S, SP, Sec) Senior Technical
> Instructor - IPexpert, Inc.
> A Cisco Learning Partner - We Accept Learning Credits!
> Telephone: +1.810.326.1444
> Fax: +1.810.454.0130
> Mailto: mgreenlee@ipexpert.com
>
> IPexpert - The Global Leader in Self-Study, Classroom-Based, Video On
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>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Todd, Douglas M.
> Sent: Thursday, February 21, 2008 12:56 PM
> To: Radioactive Frog; Cisco certification
> Cc: ccie forum
> Subject: RE: Frame-relay trafic shaping
>
> Hmm -- some light heading your way I hope and not a dark spot...
>
>
> Some correct me if I'm incorrect:
>
> When you apply QoS to a circuit it takes 75% of the bandwidth, 25% is
> set for control and IGP (etc). If you need to reserve %20 percent, I
> would assume that it's 20% of the interface bandwidth, thus a
> max-bandwidth statement must be applied. Then you are taking %20 of
> the interface bandwidth and not %20 of
> %75
> of the interface bandwidth.
>
> Thus you are working with 75% of the interface bandwidth (sh int | i
> BW) (no max-bandwidth statement).
>
> Q2: If you are not using max-bandwidth then its %20 of the %75
> interface BW.
> CIR
> is just the threshold of where you want the DE bit to be set. But
> obviously it's part of the Bc/Be formulas.
>
> Douglas
>
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
> Of Radioactive Frog
> Sent: Wednesday, February 20, 2008 7:13 PM
> To: Cisco certification
> Cc: ccie forum
> Subject: Frame-relay trafic shaping
>
> FRTS question folks,
>
> Q1. in QoS class-map statement, if we have to reserve 20% bandwidth -
> will that be calculated from Frame-relay CIR???? (CIR=95% of BW). I am
> not sure....
>
> Q2. Also if we have to allocate 20% bandwidth for signaling traffic -
> will that be calculated from CIR? or Total Bandwidth?
>
> can someone shed some light on this please....
>
>
> Frog
>
>
> interface Serial6/0
> description Parent FR Link for BRANCH#60 no ip address encapsulation
> frame-relay frame-relay traffic-shaping !
>
>
> interface Serial6/0.60 point-to-point
> description FR Sub-Interface for BRANCH#60 bandwidth 256
>
> frame-relay interface-dlci 60 ppp Virtual-Template60 ! Enables MLPoFR
> class FRTS-256kbps ! Binds the map-class to the FR DLCI
>
>
>
> !
> interface Virtual-Template60
> bandwidth 256
> ip address 10.200.60.2 255.255.255.252 service-policy output WAN-EDGE
> ! Attaches MQC policy to map-class ppp multilink ppp multilink
> fragment-delay 10 ! Enables MLP fragmentation ppp multilink interleave
> ! Enables MLP interleaving !
>
> !
> map-class frame-relay FRTS-256kbps
> frame-relay cir 243200 ! CIR is set to 95% of FR DLCI rate frame-relay
> bc
> 2432 !
> Bc is set to CIR/100 frame-relay be 0 ! Be is set to 0 frame-relay
> mincir 243200 ! MinCIR is set to CIR
>
>
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