The%20Load%20Balancing%20Schemes%20Observations

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The Load Balancing Schemes Observations

• zhaisuping_at_huawei.com
• yanw_at_huawei.com
• IEEE802.17 WG
• Orlando, Florida USA
• March 1116, 2007

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This slide observes three existing load balancing
schemes from the different aspects, giving out
the pros and cons of these different load
balancing solutions.
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RPR based technology aspect

• For TTL load balancing scheme, its based on
  the RPR technology itself, using TTL to scope the
  frame transmission, avoid the frame duplication
  and data loop, using the interconnected RPR
  stations bidirectional flooding to realize the
  load balancing.
• For the Hash load balancing scheme and VLAN
  (or other specific RPR fields) load balancing,
  the extra information (i.e. hash value, vlan id
  or other value) is introduced into the RPR
  interconnected stations to decide the forwarding
  behavior, thus realizing the load balancing and
  avoiding the frame duplication and data loop.

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Service transmission deterministic aspect

• For TTL and Hash load balancing scheme, its
  possible that the same service flow would go
  through the different interconnected RPR
  stations, possibly inducing the service Qos
  inconsistency.
• For the VLAN (or other specific RPR fields)
  load balancing, the same service flow always go
  through the same interconnected RPR station,
  ensuring the service Qos consistency.

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The shortest path aspects

• For TTL load balancing scheme, to get the
  shortest path, the network must be carefully
  provisioned, the matched nodes are opposing on
  the ring. Or else for example when the matched
  node are co-located in one box or place, its not
  the shortest path. In the casual interconnected
  ring only the path on the destination ring can be
  shortest, the total path is usually not the
  shortest one.
• For the Hash load balancing scheme and VLAN
  (or other specific RPR fields) load balancing,
  its always possible that the path traffic go
  through are not the shortest one.

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Accidentally frame duplication

• For TTL load balancing scheme, if one node on
  the ring is changed to passthrough mode when the
  flooding traffic is in flight, the frame is
  duplicated.
• For the Hash load balancing scheme and VLAN
  (or other specific RPR fields) load balancing, in
  the above situation, its possible to avoid the
  frame duplication through the unidirectional
  flooding, the frame can be stripped off the ring
  by the source address. (If bidirectional
  flooding is used, the problem still exists.)

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The tributary interface support

• For TTL load balancing scheme, when the
  interconnected stations support the tributary
  interface, in order to fully communicate with all
  the nodes across the rings and prevent the frame
  duplication, there should be some specific
  mechanism to be used.

• For the Hash load balancing scheme and VLAN (or
  other specific RPR fields) load balancing,
  interconnected stations tributary interface is
  supported as it is for the any other rings
  stations tributary interface.

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Unexpected persistent flooding

• For TTL and VLAN (or other specific RPR
  fields) load balancing scheme, the traffic paths
  are determined by the bridge learning and are
  symmetrical, there is no persistent flooding.
• For the Hash load balancing scheme, its
  possible the path that bridge learns violates the
  path picked by the hash value, to result in the
  unexpected persistent flooding.

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Interaction with xSTP

• For TTL load balancing scheme and Hash load
  balancing, both interconnected stations are
  actively forwarding traffic, there should be some
  tweaks to spoof xSTP that there are no loop path.
• For VLAN (or other specific RPR fields) load
  balancing, the network topologies is conformance
  with xSTP.

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Load balancing extent

• For TTL load balancing scheme, to which extent
  the load is balanced is dependent on the
  interconnected ring topologies and the remote
  bridge numbers behind the RPR bridge.
• For the Hash load balancing, it depends on the
  specific hash algorithm to balance the traffic.
• For VLAN (or other specific RPR fields) load
  balancing, traffic can be distributed to the
  interconnected RPR bridges by different services
  through the reasonable configuration, load can be
  balanced between the interconnected RPR bridges,
  its independent of the RPR ring topologies and
  the remote bridge numbers behind the RPR bridge.

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Thank you