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LLQ and Bandwidth reservation

Hey everyone,

I have a question about Low-latency queuing. The following is configured on my branch routers to handle VoIP traffic.

!

class-map match-all VOICE

match ip dscp ef

class-map match-any CALL-SETUP

match ip dscp af31

match ip dscp cs3

!

!

policy-map LLQ

class CALL-SETUP

bandwidth percent 4

class VOICE

priority 256

class class-default

fair-queue

!

!

!

interface Serial0/0.105 point-to-point

description Primary_Frame_To_RCC-FRAME-R1

bandwidth 768

ip address XXX.XXX.XXX.XXX XXX.XXX.XXX.XXX

no ip redirects

no ip unreachables

no ip proxy-arp

frame-relay interface-dlci XXX

class BUR_TO_RCC

crypto map OutsideInterface

!

map-class frame-relay BUR_TO_RCC

frame-relay cir 1544000

frame-relay bc 15440

frame-relay be 0

frame-relay mincir 1544000

service-policy output LLQ

!

!

Now how I understand it above, it says that any packet that matches a DSCP code of EF gets placed in the class/queue VOICE that has a guaranteed and reserved (or at least I thought) bandwidth of 256K.

The reason I say "I thought" above is because recently we backed up one of our servers at night and noticed that the transfer rate was maxed (1.5 Mbps). But if the bandwidth is supposed to be reserved for the VOICE class/queue, should my transfer rate have risen past 1.28 Mbps???

Please let me know if I am interpreting this incorrectly. Thanks much guys!!

-Lloyd

1 REPLY
Bronze

Re: LLQ and Bandwidth reservation

The reason is very simple. In your case "priority 256" tells that it can reserve bandwidth up to 256k for ACTIVE voice traffic. If there is no voice traffic, then other classes can use it or if voice traffic for eg only using 128k, then other 128k can be used by other classes.And also please note that if voice traffic presents itself more than 256k, then that excess voice traffic will be dropped.

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