The document evaluates the worst case switching delay for a unidirectional signal fail in a 16 node ring network with a maximum length of 1200 km. It considers the processing delays at switching and pass-through nodes, message validation time, and transmission delay over fiber. The total switching delay is calculated as the sum of the processing delays at nodes A through F, the intermediate node pass-through delays, and the long transmission delay over the fiber path, which is estimated as (15/16)*1200*0.005.

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3.  The switching delay for the unidirectional signal fail in the
worst case can be evaluated for a 16 nodes ring with a
maximum length of 1200 Km.
 Let Dp be the processing delay in a pass-through node, J*Dp
the processing delay in a switching node, 0,375 ms the time it
takes to validate a new message (three frames) and
assuming that transmission
 delay over a fiber system be 5 ms/Km the contributions to the
delay are:
 Consider A link between A-B-C-D-E-F
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4.  Time it takes to node F to generate first request: J*Dp
 Time it takes to the intermediate nodes to move to pass-through:
14*(Dp+0,375)
 Time it takes to node E to process the request: J*Dp+0,375
 Time it takes to node E to generate the acknowledgement request:
J*Dp
 Time it takes to the intermediate nodes to pass-through the message
from E (see note): 14*Dp
 Time it takes to node F to process the request from node E: J*Dp+0,375.
 The transmission delay over the fiber is (long path) : (15/16)*1200*0.005
 Then the total switching delay Sd is:
Sd = 4 *J* Dp + 28* Dp +16* 0.375+ 2*(15/16)* 1200*0.005
 NOTE: A node in pass-through state is supposed not to check the
incoming K-bytes for three
frames before relaying them on the outgoing signal.
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