Ideally, we would not need any security in our applications at all, instead having the luxury to focus all resources on performance. Timothy Stapko, in Practical Embedded Security, 2008 Hashing–Low Security, High Performance As traffic patterns change over time, the load distribution may become less uniform causing congestion points in the network. The key in networking applications is to find a hash algorithm that provides uniform distribution for common traffic patterns found in the network. Another nice feature is that frames belonging to the same flow (for example the same video stream) will always be hashed to the same output, maintaining in-order delivery. If a proper hash algorithm is chosen, and frames arrive with fairly random header fields, traffic will be uniformly distributed across the output ports. ![]() Instead of pointing to an entry in a table, the hash algorithm is used to select one of four possible output ports. For each frame coming into the switch, a header field or multiple header fields can be chosen to form a hash key. ![]() Let’s assume that we have a simple switch with one input and four outputs as shown in the figure. In a switch or router, a similar technique can be used to select a path for a packet to take based on information in the packet header as shown in Figure 7.12.
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