10-31-2003 08:52 AM - edited 03-02-2019 11:23 AM
We have 2 ATM connected hub 3662 routers with RS8234 SAR ATM DS3 module, each with a PVC connecting remote sites using 2621 router with FRX over 384Kbps frac T-1.
Each PVC has 192 CIR and 384 burst. Running VOIP and will use LFI and FRTS. Do not want to exceed CIR at any time to prevent packet loss for voice.
Trying to do the math to determine the best value for PCR SCR and MBS. To restrict exceeding my CIR, research says to make SCR=PCR, but the formula to determine MBS is T = (burst cells x 424 bits per cell)/(PCR-SCR). Should my MBS be 0?
The frame relay research indicates Be should be 0. Do the MBS and Be paramaters operate similarly under these circumstances?
3662 config
interface ATMA/0.ab point-to-point
ip directed-broadcast
pvc A/abc
protocol ip (ip address) broadcast
vbr-nrt 192 192 16
encapsulation aal5snap
protocol ppp Virtual-TemplateZ
interface Virtual-TemplateZ
bandwidth 192
ip address X Y
service-policy output XYZ
ppp multilink
ppp multilink fragment-delay 10
ppp multilink interleave
Frame Relay Config
interface Serial0/0.X point-to-point
no cdp enable
frame-relay interface-dlci AB ppp Virtual-TemplateX
class frts-192kbps
interface Virtual-TemplateX
bandwidth 192
ip address (IP Address)
ip mroute-cache
service-policy output ABC
ppp multilink
ppp multilink fragment-delay 10
ppp multilink interleave
map-class frame-relay frts-192kbps
frame-relay cir 192000
frame-relay bc 1920
frame-relay be 0
frame-relay mincir 192000
10-31-2003 09:15 AM
the way you have it configured is correct , when PCR is equal to SCR you will not be able to burst . you should remove the 16 it is ignoring that number
11-04-2003 10:24 PM
ATM has about 15-20% of the overhead than the Frame-relay side. So you usually config 15-20% more on the parameter for the ATM traffic shaping compare to the FRTS side.
http://www.cisco.com/warp/customer/121/frf8_shaping.html
Regards,
Bessie
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