Intra-NE/Inter-FE Topology Discovery (draft-ansari-forces-discovery-01.txt)

1
Intra-NE/Inter-FE Topology Discovery(draft-ansari
-forces-discovery-01.txt)
Furquan Ansari (Lucent) Hormuzd Khosravi
(Intel) Jamal Hadi Salim (Znyx)
2
Overview

• ForCES Element Discovery
• Provides the topology/layout of the ForCES
  elements in the NE
• Operates in the Post-Association phase of the
  ForCES protocol
• Useful for certain optimizations
• Path/Route selection from the ingress to egress
  FE
• Primary/Backup handover by FE without aid from CE
• Can be implemented as a Topology LFB on the FE

3
Discovery Mechanism

• Two distinct operational components
• FE side component that collects the FE neighbor
  information
• CE side component that collects neighbor
  information from FEs to compute complete NE
  topology
• The operation at the FE component can be divided
  into two phases
• The initial topology discovery phase
• Neighbor information is discovered/collected and
  neighbor relationships are maintained
• The topology maintenance phase
• Changes to the topology during normal operation
  are reported back to the CE

4
Assumptions and Requirements

• Each element has been configured by its
  respective PEID (CEID or FEID)
• ForCES protocol association exists between the CE
  and FE
• Discovery operates only during the
  post-association phase of the ForCES protocol
• Discovery is enabled on specified interfaces
• Probe/Hello component used for maintaining
  neighbor relationships is a pluggable component
• Can be substituted with any other mechanism such
  as BFD or proprietary, if desired

5
Topology Discovery and Maintenance Operation

• CE activates the topology LFB/component on the FE
  to initialize on specific ports
• FE topology LFB/component sends and receives
  neighbor probe/Hello messages
• FE builds a neighbor relationship table (partial
  topology)
• CE queries each FE for its neighbor table
• CE build complete topology from individual
  neighbor tables by each FE
• FE continues to send probe/Hello and updates CE
  asynchronously any new changes
• All exchanges between the CE and FE with respect
  to topology discovery are carried over the ForCES
  protocol

6
Discovery and Maintenance
CE
Neighbor Table Update
ForCES Protocol
FE1
Probe/Hello Recv
FE2
Probe/Hello Txmit
7
Example
One port LFB/interface can have multiple parallel
links between FEs
8
Conclusion

• ForCES architecture requires following services
• Inter-FE topology discovery
• Inter-FE topology maintenance (updates) during
  normal operation
• ForCES discovery mechanism presented achieves
  these services
• Currently missing piece in the ForCES
  Architecture
• Accept as Working Group Item?

9
BACKUPS
10
Inter-FE Topology Discovery and Maintenance

• CE requires consistent, real-time view of
  inter-FE topology
• Topology impacted by changes in PE or link status
• Each PE maintains neighbor relationship database
• Provides only partial topology information
• Partial topology construction at each PE
• Partial topology exchange between FE and CE
  occurs only after ForCES association is complete
• Uses the ForCES protocol (using event driven
  topology query/response messages)
• CE aggregates all partial topologies and
  constructs the complete inter-FE topology
• Installs appropriate FIB entries (on FE) for
  packet forwarding within the NE