US Robotics USR2410 Manual de usuario descargar pdf (Pagina 32)

were translated using that flow mapping. Packets would also be mapped based on if they matched

the reverse of that mapping, in order to return packets to their original sender.

Each pattern in the IPRewriter element had a corresponding input. For example, the first pattern

would accept packets on the first input. After the pattern, an output was defined for the forward

and reverse paths. For simplicity, in the configuration files created, the output for forward path of

the first input was the first output, and so forth. The reverse output would correspond to the

forward output of the other mapping pattern.

5.1.2

ICMPPingRewriter

This element is similar to the IPRewriter, but preformed NAT only on ICMP echo packets. It did

not have the same amount of flexibility as the IPRewriter. It was configured to change the source

address to correspond with that of the host router, and leave the destination address unchanged.

Requests were sent to the first output, replies were sent to the second output.

5.1.3

ICMPRewriter

This element was used to check mappings for ICMP error packets. It checked the patterns used in

the IPRewriter and ICMPPingRewriter elements. If a mapping existed, it was applied, and the

packet sent to output zero. If not, the packet was sent unchanged to output one.

5.1.4

GatewayDevice: Compound Element

This element manages packet flow between Click and a communication device. In the network

implemented, this communication device was the client wireless device or wired Ethernet device.

As shown in Figure 5-1, packets coming from the device were sent through to the next element

within the Click router. Packets destined for the external network were first sent to a queue, from

the queue packets were sent to the device. Since this element could not write to and read from the

device at the same time a schedule was created. The schedule was such that the packets where

sent to the device ten times more often than read from the device.

Figure 5-1: Gateway Device Interaction Diagram

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US Robotics USR2410 Manual de usuario Pagina 32