Cisco TelePresence Administrator's Manual page 229

Bandwidth control
About subzones
A traversal call between two endpoints within the same subzone must, like all traversal calls, pass through
the Traversal Subzone. This means that such calls consume an amount of bandwidth from the originating
subzone's total concurrent allocation that is equal to twice the bandwidth of the call – once for the call from
the subzone to the Traversal Subzone, and again for the call from the Traversal Subzone back to the
originating subzone. In addition, as this call passes through the Traversal Subzone, it will consume an
amount of bandwidth from the Traversal Subzone equal to that of the call.
Cisco VCS Administrator Guide (X8.1.1) Page 229 of 507