802.17c Protected Inter-Ring Connection

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802.17cProtected Inter-Ring Connection

• Rafi Ram - Corrigent Systems
• January 2007

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802.17c Proposed Requirements

• Backwards compatible with non-802.17c stations
• Support rings interconnect through dual-station
  homing
• Provide sub 50msec protection
• Allow for hash based load balancing using both
  stations
• The load balancing shall allow unicast forwarding
  (prevent persistent flooding)
• Support for local tributary interfaces in
  interconnecting stations
• Prevent loops in normal and protection states,
  and during the transient process between the
  states

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802.17c Proposed Requirements (cont)

• Support both point-to-point and
  multi-point-to-multi-point services
• Support network topology of collector ring with
  multiple subtending rings
• Support for efficient selective MAC table flush
• Attend the MAC table scalability issue
• Provide maintenance commands (e.g. manual
  switch-over)
• Allow implementation of interconnecting station
  as two separate stations with back-to-back
  connections

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Network Topology of Collector Ring with
Subtending Rings
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Suggested Solution

• Backwards compatible with non-802.17c stations
• Transparent for non-interconnecting stations
• Minimal overhead of provisioning, protocol
  messages, database and state-machines
• The basic suggestion resolve all proposed
  requirements (with the exception of static MAC
  entries)
• An additional enhancement can be suggested to
  addresses the MAC table scalability issue

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Definitions

• Stations A B are members of a protection group
  (PG) for interconnect in ring 1 with ring 2
• Stations A B are members of a (different)
  protection group for interconnect in ring 1 with
  ring 3
• Each protection group is provisioned with a ring
  wide unique identifying index PGI
• One of the stations in a PG is provisioned as the
  0 member, and the other as the 1 member

PGM protection group member
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Provisioning Example

• PGI 101 is provisioned in ring 1 for interconnect
  with ring 2
• station A is provisioned in ring 1 as PGI member
  101.0
• station B is provisioned in ring 1 as PGI member
  101.1
• PGI 102 is provisioned in ring 1 for interconnect
  with ring 3
• station A is provisioned in ring 1 as PGI member
  102.0
• station B is provisioned in ring 1 as PGI member
  102.1

There is no need to provision stations A B as
PG in ring 2 or 3
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Frame Forwarding

• The forwarding of frames between the rings
  through the interconnect shall be based on the
  switching method implemented by the station
  client (layer 2 or layer 3)
• For example, in case of layer 2 switching
• MAC table learning shall be done in the
  inter-connecting station on frames forwarded
  between the rings
• Multicast and broadcast shall be forwarded though
  interconnect
• Unicast frames with relevant matching entries in
  the MAC table shall also be forwarded though the
  interconnect

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Load Balancing

• To allow for load balancing, the protection group
  members shall use hash function to distribute the
  inter-connecting traffic between them
• The hash function should be flow based
• For example, if both inter-connecting member
  stations are active then
• the 0 member station shall not forward
  (discard) frames with odd hash result
• the 1 member station shall not forward frames
  with even hash result

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PGM Status Message

• Protection group member status messages are used
  to advertises the state of the interconnect
  functionality to the mate PG member
• The PGM status message is a broadcast frame. The
  message can be a new control type or a new OAM
  type
• The frame shall contains multiple entries, an
  entry per protection group that the station
  participates
• A message entry consists of the PG index, 0 or
  1 configuration and interconnect functionality
  state