Co-operative Server Pool for Hotspot Rescue Service

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Co-operative Server Pool for Hotspot Rescue
Service

• Weibin Zhao
• Henning Schulzrinne

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Outline

• Problem space for hotspot
• Alleviating hotspot
• Co-operative server pool
• Previous experience

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Problem space for hotspot
Place
network
server
Object
Small web
Large file
Stored media
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Alleviating hotspot
Load Balancing
Hotspot Rescue
Hotspot Avoidance
Co-operative Server Pool
Smart Client
P2P
Server Selection
Caching
Service Migration
Client Redirection
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Co-operative server pool (CSP)

• ? MASH (mutual aid society for hotspots)
• Form server pool ()
• Server pool architecture ()
• Rescue vs. local service
• Monitor servers in the pool ()
• Predict and detect hotspot
• Select candidate for migration ()
• Client re-direction ()

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Form server pool

• Membership service
• Static configuration
• DHCP
• Dynamic membership via advertisement
• Overlap server pool
• Multiple scopes

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Server pool architecture

• Full mesh
• Autonomous, peer to peer
• Simple, reliable
• Scalability O(10)
• Other topology
• Spanning tree
• Two-level tree mesh

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Monitor server in the pool

• What to do?
• Aliveness
• Load information
• How?
• Direct for neighbors in mesh/tree
• Indirect for tree

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Migration

• Select candidate
• Available resources at candidate
• Network path to candidate
• Migration cost
• Potential performance gains

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Client re-direction

• Mechanisms
• Refer ()
• Tunnel
• DNS
• Evaluation

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Previous experience

• mSLP
• Mesh-enhanced service location protocol
• Remote SLP discovery
• DNS SRV
• Gateway selection for IP telephony

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mSLP

• Full mesh server pool
• Membership service
• Data exchange
• Update forwarding
• Initial data exchange
• Multi-scope server pool
• Use scopes for scalability
• Flexible for different purposes

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Full-mesh multi-scope server pool
Server1 (E,B)
(E)
(B)
(L)
Server3 (L,E)
Server2 (B,L)
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Remote SLP discovery

• Three configurations
• Small only SAs
• Medium DAs in one scope
• Large DAs in multiple scopes
• DNS SRV
• All servers should be equivalent
• Gateway DAs for small/large configurations

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Gateway DAs
SA1
SA2
DA1 (Sa)
SA3
SA4
DA2 (Sb)
Gateway DA
Gateway DA
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Gateway selection for IP telephony

• Service template
• Total capacity, remaining capacity, prefix list
  (destination), cost list, ASR (answer-seizure
  ratio) list
• Location server gateways
• Gateway register
• Location server directory service
• Direct client call to gateway

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Gateway selection
Gateway1
Location Server
Incoming call
Gateway2
Gateway3
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Big Picture

• Where to put the intelligence
• In front of servers
• With server
• _at_ client
• In the middle directory server

Server1
Directory
Client
Server2