This concept is the one who makes the routers such as Cisco have the excellent performance they have.

In the new Cisco IOS for example, the operating system as such is not the system that takes care of routing. In Cisco this is called the CFE or Cisco Forwarding Engine. The philosophy is that the Operating System is a program with the administration and configuration, but the handling of the complete package makes it the CFE.

When a Cisco router receives a packet the card generates an interrupt. If this is the first destination of a package on the table, IOS sends a call procesoel which revises the routing table (depends on the protocol) and based on this stored in memory fate and full-header Ethernet.

This makes sense because you know that after this package come thousands of more packages to the same destination, change the IP packet and routing.

The magic is to receive the second set onwards, where the same interrupt the network card query this table in memory, replacing the IP, add Ethernet headers and places the package into the buffers of the interface output. All in the same interrupt, and without intervention of IOS per se.

Obviously so far I have only spoken of software, but the algorithms and memory structures are optimized for very low level, the hardware that form a crucial part of design.
Examples of these are the buses designs exclusively for communication between network cards, in order to expedite the transfer of data, among others. That is why although the routers are much less
memory and a server processor that their performance is of high standard.

Likewise the ability of the device containing packages or backplain, which is an important criterion in the selection of equipment.

Another characteristic of hardware is the ability of cisco to reallocate memory (if needed memory to store packages, the same IOS-based resources) or buses.

A Cisco router has the ability to take control of other buses and giving it to transport data as a first priority, before any other interrupt. This is because their designs, as a cisco router often locks or freezes, and we have no access to console, but despite this the team continues ruteando packages. This is because the IOS is not the core of routing, but the CFE.

Now it has emerged a new generation of IOS high-level PSI or higher in each of these cards in the chassis has small threads or instances of IOS, which can cooperate with each other to
make more efficient routing.

Collaboration | Gerardo Amaya

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