ZyXEL ZyWALL ATP700 User Guide - Page 346
Policy Routing Technical Reference, Routing Protocols Overview
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Chapter 10 Routing 10.4 Policy Routing Technical Reference Here is more detailed information about some of the features you can configure in policy routing. NAT and SNAT NAT (Network Address Translation - NAT, RFC 1631) is the translation of the IP address in a packet in one network to a different IP address in another network. Use SNAT (Source NAT) to change the source IP address in one network to a different IP address in another network. Assured Forwarding (AF) PHB for DiffServ Assured Forwarding (AF) behavior is defined in RFC 2597. The AF behavior group defines four AF classes. Inside each class, packets are given a high, medium or low drop precedence. The drop precedence determines the probability that routers on the network will drop packets when congestion occurs. If congestion occurs between classes, the traffic in the higher class (smaller numbered class) is generally given priority. Combining the classes and drop precedence produces the following twelve DSCP encodings from AF11 through AF43. The decimal equivalent is listed in brackets. Table 133 Assured Forwarding (AF) Behavior Group CLASS 1 CLASS 2 Low Drop Precedence AF11 (10) AF21 (18) Medium Drop Precedence AF12 (12) AF22 (20) High Drop Precedence AF13 (14) AF23 (22) CLASS 3 AF31 (26) AF32 (28) AF33 (30) CLASS 4 AF41 (34) AF42 (36) AF43 (38) Maximize Bandwidth Usage The maximize bandwidth usage option allows the Zyxel Device to divide up any available bandwidth on the interface (including unallocated bandwidth and any allocated bandwidth that a policy route is not using) among the policy routes that require more bandwidth. When you enable maximize bandwidth usage, the Zyxel Device first makes sure that each policy route gets up to its bandwidth allotment. Next, the Zyxel Device divides up an interface's available bandwidth (bandwidth that is unbudgeted or unused by the policy routes) depending on how many policy routes require more bandwidth and on their priority levels. When only one policy route requires more bandwidth, the Zyxel Device gives the extra bandwidth to that policy route. When multiple policy routes require more bandwidth, the Zyxel Device gives the highest priority policy routes the available bandwidth first (as much as they require, if there is enough available bandwidth), and then to lower priority policy routes if there is still bandwidth available. The Zyxel Device distributes the available bandwidth equally among policy routes with the same priority level. 10.5 Routing Protocols Overview Routing protocols give the Zyxel Device routing information about the network from other routers. The Zyxel Device stores this routing information in the routing table it uses to make routing decisions. In turn, the Zyxel Device can also use routing protocols to propagate routing information to other routers. ZyWALL ATP Series User's Guide 346