Nortel Web OS 10.0, Application Manual

Page: 283 / 482

Web OS 10.0 Application Guide
Chapter 11: High Availability
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212777-A, February 2002
Stateful Failover of Layer 4 and Layer 7
Persistent Sessions
Web OS provides stateful failover of content-intelligent persistent session state and Layer 7
persistent session state. This includes the following:
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SSL session state
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HTTP cookie state
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Layer 4 persistent
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FTP session state
Providing stateful failover enables network administrators to mirror their Layer 7 and Layer 4
persistent transactional state on the peer switch.
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Stateful failover does not synchronize all sessions, except persistent sessions. Make
sure Direct Access Mode (DAM) is enabled when you configure stateful failover for Layer 7
persistency (for example: SSL session ID persistence-based server load balancing, URL and
cookie-based server load balancing).
To provide stateful failover, the state of the connection and session table must be shared
between the switches in high-availability configurations. With Virtual Matrix Architecture
(VMA) enabled, all URL and cookie-parsing information is stored in the session table on port
9. Sharing this information between switches is necessary to ensure the persistent session goes
back to the same server.
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Stateful failover is only supported in active-standby mode with VMA enabled.