Michael MelliarSmith

1
AFOSR Multidisciplinary University Research
ProgramProtocol Engineering Research Center
Performance ofMulticast Protocols for CORBA

Michael
Melliar-SmithDepartment of Electrical
Computer EngineeringUniversity of California,
Santa BarbaraJon Sjogren, Program Manager
2
Group Multicast Protocols

• Typical group multicast protocols are designed
  for
• Complex applications
• Many concurrent activities
• High message traffic
• Performance is determined by time spent in queues
• Time spent in queues is determined by throughput
• Our Totem protocol is designed for throughput
• Flow control
• No collisions on the Ethernet, allows high
  utilization
• Collects several messages to transmit in a batch
• Must wait for the token keep the ring small

3
Embedded Applications

• Typical embedded applications
• Simple with fewer messages
• Impose low load on the network
• Message delivery latency is critical
• Message order is determined by priorities
• Totem is not designed for embedded applications
• Waiting for the token increases the latency
• Extra Totem process increases the latency
• Message order ignores priorities

4
Experimental Testbed

• Pluggable FT Infrastructure with Totem
• Three-way replicated server, unreplicated client
• 1KByte payload in request and reply messages
• Four Pentium III PCs, single 1GHz CPU, 256 RAM,
  Linux Mandrake 7.2 OS
• 100 Mbps FastEthernet LAN
• eOrb from Vertel

5
Latency Measurements
Latency in ?seconds
6
Latency for a Simple Request/Reply
7
Sending Delay
Semi-Active Replication
8
Fault Detection and Recovery Time

• Crash fault detection time 3 ms
• Recovery time 100 ms

9
Performance
Three-Tier Application
Stores Records
for Account A
Account A
G1
G2
Gateway
Gateway
AccountManager
OTS Server
Backup
Backup
Backup
Backup
Primary
Primary
Stores Records
for Account B
Account B
Client
Application Server
Database
10
End-to-End Performance Three-Tier Application
Latency
Throughput
11
Performance
Three-Tier Application
Application Logic Processing Time
2PC Processing Time
12
Summary

• Group multicast protocols, such as our
  Totem protocol, are designed for complex
  applications and achieve high throughput
• For applications that require low latency,
  such as real-time embedded applications,
  a different
  approach is required