Dynamic Bandwidth Allocation on Cisco Routers

[Steven van Jaarsveld]

Hi Forum

I am busy investigating this but am currently coming up with no solutions other than additional appliances that need to be installed. What I am trying to achieve is the following:

I have a Subscriber based connection (users connect with DSL links) and they are authenticated against my Radius Server. IP Addresses are assigned dynamically as well. This is done using the Cisco ISG functionality on the Cisco ASR. What I need to be able to do now is to allow the router to dynamically allocate QoS templates/bandwidth allocation based on a contention ratio of 10:1 across the access link so across a 10Mb link I can have 10 users accessing the link at 10Mb but when the 11th user connects the bandwidth needs to be dynamically increased on the interface (underlying physical link has enough bandwidth capacity) and so on. When a user disconnects the bandwidth needs to be dynamically decreased again so that the contention ratio always remains at 10:1

This is a very brief overview of what I am trying to achieve. Is there anyone here that can help me by pointing me in the right direction to achieve this even if it means by using an additional appliance-based or software-based system

Regards

Steven

[tariq83]

Hello Mr. Steven,

Did you find the solution?

If yes please share it.

Best regards,

Tariq

[Georg Pauwen]

Hello,

not sure if this is what you are looking for, but maybe an alternative would be to a parent/child shaper that limits the bandwidth to 1MB per user, and in case it is not used, the other users get all remaining bandwidth. Below is an example for two users:

class-map match-all CLASS_1

match access-list 101

!

class-map match-all CLASS_2

match access-list 102

!

access-list 101 permit ip host 192.168.1.2 any

access-list 101 permit ip host 192.168.1.3 any

policy-map CHILD_SHAPER
class CLASS_1
priority 1024
class CLASS_2
priority 1024
class class-default
fair-queue
!
policy-map PARENT_SHAPER
class class-default
shape average 10240000
service-policy CHILD_SHAPER

[tariq83]

Hello Georg,

I have Cisco BRAS 7206VXR configured for PPPoE sessions.

interface GigabitEthernet0/2
no ip address
pppoe enable group global
!

RADIUS is pushing the following:

BRAS-Access:PPP,
Cisco-AVpair=lcp:interface-config#1=rate-limit output $O:cBWOut$ conform-action continue exceed-action drop,
Cisco-AVpair=lcp:interface-config#1=rate-limit input $O:cBWIn$ conform-action continue exceed-action drop,

cBWOut=20000000 3750000 7500000

cBWIn=10000000 1875000 3750000

When the PPPoE user authenticated it has a virtual interface.

-bras#sh users
Interface User Mode Idle Peer Address
Vi3 user1 PPPoE 03:35:24 192.168.5.25

-bras#sh int vi3 configuration
Virtual-Access3 is a PPP over Ethernet link (sub)interface

Derived configuration : 437 bytes
!
interface Virtual-Access3
ip unnumbered GigabitEthernet0/1
rate-limit input 10000000 1875000 3750000 conform-action continue exceed-action drop
rate-limit output 20000000 3750000 7500000 conform-action continue exceed-action drop
no logging event link-status
timeout absolute 480 0
no snmp trap link-status
peer default ip address pool insta
ppp authentication pap chap
ppp ipcp address required
ppp ipcp address unique
end

We are selling a 20 Mbps plan to customers with a contention ratio of 1:10.
This means that the parent speed-limit of 20 Mbps and under this parent, a user maximum speed-limit will be 20Mbps.
if the line is free and one user starts to download, this user will get the full 20 Mbps throughput.
In the case that a second user starts actively downloading, they will receive 10 Mbps each.
When all 10 users are simultaneously downloading they will share the parent bandwidth - each should get 2Mbps minimum speed.
Where minimum value makes sure that any heavy downloading user must not take over all 20Mb and left other users with no bandwidth.

I am not able to find a configuration in Cisco how to achieve the above.

best regards,

Tariq