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Cisco ONS 15310-MA SDH Reference Manual, Release 9.1 and Release 9.2
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Chapter 7 Circuits and Tunnels
Server Trails
The server trail link is bidirectional and can be VC3, VC11, VC12, VC4, VC4-2c, VC4-3c, VC4-4c,
VC4-6c, VC4-8c, VC4-12c, VC4-16c, VC4-32c, and VC4-64c; you cannot change an existing server
trail to another size. It must be deleted and recreated. A circuit provisioned over a server trail must match
the type and size of the server trail it uses. For example, an VC4-3c server trail can carry only VC4-3c
circuits and not three VC4 circuits.
Note There is no OSPF or any other management information exchange between NEs over a server trail.
7.12.1 Server Trail Protection Types
The server trail protection type determines the protection type for any circuits that traverse it. A server
trail link can be one of the following protection types:
• Preemptible—PCA circuits will use server trails with the Preemptible attribute.
• Unprotected—In Unprotected Server Trail, CTC assumes that the circuits going out from that
specific port will not be protected by provider network and will look for a secondary path from
source to destination if you are creating a protected circuit.
• Fully Protected—In Fully Protected Server Trail, CTC assumes that the circuits going out from that
specific port will be protected by provider network and will not look for a secondary path from
source to destination.
Note Only SNCP protection is available on server trails. MS-SPRing procection is not available on server trail.
7.12.2 VCAT Circuit Routing over Server Trails
An VC4-3c server trail can be used to route VC4-3c circuits and an VC4 server trail can be used to route
VC4 circuits. Similarly, a VC3 server trail can be used to route VC3 circuits.
For example, to route a VC4-3c-2v circuit over a server trail, you must enable split fiber routing and
create two VC4-3c server trails and route each member manually or automatically over each server trail.
To route a VC4-12c-2v circuit over a server trail, you must enable split fiber routing and create two VC4
server trails and route each member manually or automatically over each server trail.
Note Server trails can only be created between any two optical ports or STM-1E ports.
VCAT circuities can be created over server trails in the following ways:
• Manual routing
• Automatic routing
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Diverse routing: This method enables VCAT circuit routing over diverse server trail links.
Note When creating circuits or VCATs, you can choose a server trail link during manual circuit routing. CTC
may also route circuits over server trail links during automatic routing. VCAT common-fiber automatic
routing is not supported.
