= The traversal subzone is a conceptual subzone that does not have any registered endpoints. Its sole purpose is to control the bandwidth that is used by traversal calls. Traversal calls are calls that pass through a firewall or a NAT device, using a pair of Expressways (one acting as a traversal client and the other as a traversal server). The traversal subzone allows theadministrator to set a limit on the total bandwidth that can be used by traversal calls, as well as the bandwidth per call. This helps to optimize the network resources and prevent congestion123 References := 1Concept of Zones Demystified On Cisco Expressway Series 2Cisco Expressway Administrator Guide (X14.3) - Clustering and Peers 3Cisco Expressway Administrator Guide (X14.0) - Bandwidth Control