How to use Child Equalization to Share Bandwidth between VLANs

How to use Child Equalization to Share Bandwidth between VLANs


Child Equalization Description 

At times there are requirements to distribute bandwidth equally among objects other than hosts.
 
A clear example here is in the hospitality industry where hotels designate a unique VLAN to each room, by doing this there needs to be a way to share bandwidth between rooms before any host or user caps get applied allowing ALL rooms by default to share the available bandwidth. 

This feature will allow this and as always when a room does not use its allocated bandwidth it will be instantly shared to those rooms/VLANs that can use the bandwidth ensuring that maximum use is made of the available bandwidth at all times.

To enable this, a new feature has been added to policies found in Egress Policy Maps, known as “Child Equalisation”.which when set and used by multiple other objects will cause the bandwidth to be shared equally between the sharing objects.

So how does this work, basically a VLAN is a sub-interface which always belongs to a parent physical interface and as such shares bandwidth from that interface. As a sub-interface it has a “Parent EFC” parameter which in the past has been left blank which causes the STM to use the “default” EFC associated with the physical interface, which is actually loaded with the Rate configured to the physical interface. This enables the STM to recognize who should be in control, the physical interface rate or the vlan sub-interface rate or an Egress Policy entry in the Egress Policy Map associated with the VLAN. Viewed in diagram form the old method would have paths as shown below:


To change this to fairly share bandwidth across ALL VLANs it would be necessary to add a VLAN policy to the Physical Interfaces Egress Policy Map give it the rate it is allowed to share and set the “Child Equalization” option, then once added configure the parent_efc field for each VLAN sub-interface to use the VLAN policy in the Physical Interfaces EMAP as shown next:



Configuration Example

To use this new feature it is necessary to explain using a practical example, we will assume that a set of ACLs, EFCs and IFCs exist to classify traffic for all-ip and layer2 traffic and this example will add the components required to configure child equalization for use with multiple VLAN sub-interfaces.

While it is always possible to use the same Egress Policy Map on ALL interfaces and sub-interfaces it is best for this example to create separate Egress Policy Maps, one for the Physical Interfaces and a separate and different one for the VLAN sub-interfaces.

WARNING: - DO NOT host equalize any policies in the VLAN Egress Policy Map directly below the child equalized policy – if host equalization is require contact support for help with your configuration.

The minimal Egress Flow Class list would therefore be:


  • all-ip – which will form a bandwidth partition for ALL IPv4 and IPv6 traffic
  • layer2 – carries ALL traffic that is not encapsulated with an IP header
  • vlan-partition – this forms the bandwidth pool which will be child equalized for all VLANs
Using REST these could be created with the following commands:
  • /opt/stm/target/c.sh POST efcs/ name all-ip
  • /opt/stm/target/c.sh POST efcs/ name layer2
  • /opt/stm/target/c.sh POST efcs/ name vlan-partition
Using the CLI the commands would be:
  • egress_flow_classes all-ip description 'EFC for ALL IPv4 and IPv6 data'
  • egress_flow_classes layer2 description 'EFC for non-ip traffic'
  • egress_flow_classes vlan-partition description 'EFC that ALL VLAN sub-interfaces can share'
The next step would be to create the needed Egress Policy Maps, one for the physical interfaces and one for the VLAN sub-interfaces, for the this example we will use interface-epm and vlan-epm with the interface-epm containing the bandwidth partition that is used by the VLAN sub-interfaces to obtain their share of the available bandwidth which is then further shared between all hosts using the VLAN according to the VLANs Egress Policy Maps rules.

The interface-epm can be created with the following REST commands: -
  • /opt/stm/target/c.sh POST epms/ name interface-epm
  • /opt/stm/target/c.sh POST epms/interface-epm/policies/ name all-ip rate 1000000 host_eq true
  • /opt/stm/target/c.sh POST epms/interface-epm/policies/ name vlan-partition rate 1000000 child_eq true
  • /opt/stm/target/c.sh POST epms/interface-epm/policies/ name layer2 rate 100000 ass true
Using the CLI the commands would be:
  • egress_policy_map interface-epm exit
  • egress_policy_map interface-epm policies vlan-partition rate 1000000 child_equalisation
  • egress_policy_map interface-epm policies all-ip rate 1000000 host_equalisation
  • egress_policy_map interface-epm policies layer2 rate 100000 assured
Notice that the vlan-partition policy entry is configured for child equalization and is in the Egess Policy Map associated with the parent interface of the VLAN sub-interfaces below. Prior to this enhancement a sub-interface was always a chile of the physical interface and the bandwidth was shared automatically without equalization. 

The vlan-epm would be can be configured with the following REST commands:
  • /opt/stm/target/c.sh POST epms/ name vlan-epm
  • /opt/stm/target/c.sh POST epms/vlan-epm/policies/ name all-ip rate 1000000
  • /opt/stm/target/c.sh POST epms/vlan-epm/policies/ name layer2 rate 100000 ass truu
Using the CLI the commands would be:
  • egress_policy_map vlan-epm exit
  • egress_policy_map vlan-epm policies all-ip rate 1000000 host_equalisation
  • egress_policy_map vlan-epm policies layer2 rate 100000 assured
Physical interfaces are configured as normal in that you merely associate an Egress Policy Map with each interface, so if we are using system interfaces stm2 and stm3 the REST commands for configuration would be:
  • /opt/stm/target/c.sh POST interfaces/ name stm2 type eth egress_policy_map interface-epm rate 1000000
  • /opt/stm/target/c.sh POST interfaces/ name stm3 type eth egress_policy_map interface-epm rate 1000000 internal true
Using the CLI the commands would be: -
  • interface stm2 rate 1G egress_policy_map interface-epm
  • interface stm3 rate 1G egress_policy_map interface-epm
As you can see these are a standard pair of configuration entries. Now for the VLAN sub-interfaces which have a parent_efc field that is used to point to the vlan-partition contained in the parent interfaces Egress Policy Map, for this example we will consider VLAN tags 100 and 200 are in use making the configuration commands for REST to be:
  • /opt/stm/target/c.sh POST interfaces/ name stm2.100 type vlan parent_efc vlan-parition egress_policy_map vlan-epm rate 1000000
  • /opt/stm/target/c.sh POST interfaces/ name stm3.100 type vlan parent_efc vlan-parition egress_policy_map vlan-epm rate 1000000 internal true
  • /opt/stm/target/c.sh POST interfaces/ name stm2.200 type vlan parent_efc vlan-parition egress_policy_map vlan-epm rate 1000000
  • /opt/stm/target/c.sh POST interfaces/ name stm3.200 type vlan parent_efc vlan-parition egress_policy_map vlan-epm rate 1000000 internal true
Using the CLI the commands would be:
  • interface stm2.100 type vlan parent_efc vlan-partition egress_policy_map vlan-epm 
  • interface stm3.100 type vlan parent_efc vlan-partition egress_policy_map vlan-epm internal true
  • interface stm2.200 type vlan parent_efc vlan-partition egress_policy_map vlan-epm 
  • interface stm3.200 type vlan parent_efc vlan-partition egress_policy_map vlan-epm internal true
Thus the above commands using the parent_efc redirect bandwidth allocation from the interface rate associated with the physical interface to an Egress Policy Map Policy included in the parent interfaces Egress Policy Map.

Full Example REST Configuration

#!/bin/bash
shopt -s expand_aliases
alias zz=/opt/stm/target/c.sh
# Create required Access Control Lists - one for non IP traffic
# and a second for ALL IP traffic
zz POST acls/ name layer2
zz POST acls/layer2/entries/ name layer2 ethertype 0
zz POST acls/ name all-ip
zz POST acls/all-ip/entries/ name all-ip
# Create the Egress Flow Classes used as Bandwidth paritions in the Egress Policy Map
zz POST efcs/ name all-ip
zz POST efcs/ name layer2
zz POST efcs/ name vlan-partition
# Create the Ingress Flow Classes or Classifiers
zz POST ifcs/ name all-ip acl all-ip efc all-ip
zz POST ifcs/ name layer2 acl layer2 efc layer2
# Create the Egress Policy Map and add the policies to create the bandwidth partitions
zz POST epms/ name interface-epm
zz POST epms/interface-epm/policies/ name all-ip rate 1000000 host_eq true
zz POST epms/interface-epm/policies/ name vlan-partition rate 1000000 child_eq true
zz POST epms/interface-epm/policies/ name layer2 rate 100000 ass true
zz POST epms/ name vlan-epm
zz POST epms/vlan-epm/policies/ name all-ip rate 1000000
# Create the Ingress Policy Map and add the classification policies to handle all traffic
zz POST ipms/ name ipm 
zz POST ipms/ipm/policies/ name all-ip sequence 10000 reverse 1
zz POST ipms/ipm/policies/ name layer2 sequence 11000
# Now create the Interfaces, link to the policy maps and enable
zz POST interfaces/ name stm2 type eth egress_policy_map interface-epm rate 1000000
zz POST interfaces/ name stm3 type eth egress_policy_map interface-epm rate 1000000 internal true
zz PUT interfaces/stm2 ingress_policy_map ipm
zz PUT interfaces/stm3 ingress_policy_map ipm
zz PUT interfaces/stm2 peer stm3
zz PUT interfaces/stm2 state enabled
zz PUT interfaces/stm3 state enabled # Create sub interfaces to carry vlan tagged packets
zz POST interfaces/ name stm2.100 type vlan parent_efc vlan-partition egress_policy_map vlan-epm rate 1000000
zz POST interfaces/ name stm3.100 type vlan parent_efc vlan-partition egress_policy_map vlan-epm rate 1000000 internal true
zz PUT interfaces/stm2.100 ingress_policy_map ipm
zz PUT interfaces/stm3.100 ingress_policy_map ipm
zz PUT interfaces/stm2.100 peer stm3.any
zz PUT interfaces/stm2.100 state enabled
zz PUT interfaces/stm3.100 state enabled
zz POST interfaces/ name stm2.200 type vlan parent_efc vlan-partition egress_policy_map vlan-epm rate 1000000
zz POST interfaces/ name stm3.200 type vlan parent_efc vlan-partition egress_policy_map vlan-epm rate 1000000 internal true
zz PUT interfaces/stm2.200 ingress_policy_map ipm
zz PUT interfaces/stm3.200 ingress_policy_map ipm
zz PUT interfaces/stm2.200 peer stm3.any

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