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The difference between L1 and L2 cache of Web Content Filter (WCF)

Web Content Filter (WCF) is a feature that allows network administrator to block or pass websites by category.When WCF is used, router sends query to WCF server to ask about the category of the URL which LAN clients are trying to access, then determine whether they should be accepted or not according to the Firewall/CSM rule. And when the router done a category checking, it caches the results of the queries. There are two types of WCF cache: L1 cache and L2 cache.

WCF cache

 

What is L1 cache?

L1 cache stores the category of the URL which has been accessed previously, so that the router won’t need to send a query again if the URL has already been checked. Vigor Router is able to store category for up to 5,000 URL. L1 cache has no expiring time, entries will be deleted only when the cache is full; however, it can be deleted manually by telnet command “csm wcf flush”.

 

What is L2 cache?

Usually a webpage contains several URL for the contents and images, and it is unnecessary to check all the categories of every URL in the same webpage, this is when L2 cache comes into play. When the first URL of a webpage request has been checked and passed, router caches the source IP and destination IP, and pass all the traffic from the same source IP to the same destination IP for about one second, which is approximately the time for a webpage to be fully loaded. After that, L2 cache will be cleared.

 

Summary

In summary, L1 cache stores the category of URL previously visited until the cache is full; L2 cache stores the IP address that has passed by firewall rules for about one second. Disable both of them ensures more accurate URL categorization; however, It is recommended to enable both of them to have the fastest web-browsing processing. 

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