<p><a href="http://www.osa-jon.org/virtual_issue.cfm?vid=16">Feature Issue on High Availability in Optical Networks</a></p>In generalized multiprotocol label switching (GMPLS) architecture, the control channels between each pair of optical nodes are not forced to use the same physical link as the data/transport channels. The problem arises when, due to the fact of allowing the control channels to be physically diverse from the associated data links, there may not be any active control channels available while data channels are still in use. Control-channel faults should not have a service impact on the existing connections; that is, a link that is carrying data traffic must not be torn down because the control channel is no longer available. But, due to the lack of the control channel, the active traffic that is using the data link may no longer be guaranteed with the same level of recovery service (protection or restoration). Under these circumstances the link must be considered to be in a degraded state. This means that routing and signaling should be notified that new connections are not accepted and the link is advertised with no unreserved resources. For this purpose, here we propose a control-channel multifailure management mechanism involving routing, signaling, and link management with extended GMPLS-based protocol extensions to keep the same level of service (in terms of provisioning and recovery) when a link is in the degraded state.
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