Cisco ASR 5000 Series, Обзор продукта

Страница: 708 / 992

Content Filtering Support Overview
▀ URL Blacklisting Support
▄ Cisco ASR 5000 Series Product Overview
OL-22938-02
Step 3
The blacklist file is auto-detected by the Session Controller (SessCtrl), which verifies the integrity of the Blacklist
database using checksums, and then loads it.
The new blacklist is loaded only if it has been received properly. If the full Blacklist database is not found,
corrupted, or if the loading fails, traps are generated. Correspondingly clear traps are also generated on a valid
Blacklist database being available, and after a successful load.
Step 4 The SessMgrs read the file and load the blacklisted URLs in a local in-memory database.
Important:
The URL Blacklisting feature is enabled only if the url-blacklisting action is set in any of
the rulebases. Thus, the automatic detection of the Blacklist database, storing it in memory, and loading onto
the SessMgrs will happen only if the url-blacklisting action is set in any of the rulebases.
Step 5
The Blacklist database is loaded on each SessMgr as and when they come up (if URL Blacklisting is set in any
rulebase) or when URL Blacklisting gets set in any of the rulebases.
When the SessMgrs start for the first time or after recovery, if URL Blacklisting is set in any of the rulebases,
the stored Blacklist database at SessCtrl is loaded onto the SessMgrs. This holds true for standby managers as
well i.e., when standby managers come up the Blacklist database is loaded onto them.
Whenever a SessMgr is killed, standby manager which already has the Blacklist database loaded takes its
place, and a new standby manager is created which loads the Blacklist database as part of SessMgr getting
started for the first time.
If SessCtrl is killed, while recovering it checks if URL Blacklisting is set in any of the rulebases, if set it will
store the Blacklist database onto itself and load all the SessMgrs as well.
Step 6
When a new Blacklist database is loaded on to the SessMgrs, the new database (and any stored versions that have rolled
over) are synced to the other SPC so that after switchover, the proper Blacklist database can be accessed.
URL Blacklisting Action
The following steps describe how the URL Blacklisting feature works:
Step 1
When an initial HTTP/WAP request comes for ECS processing and is processed by the ECS subsystem, a check is
made to see if the URL Blacklisting support is enabled.
Step 2
If enabled, the URL is extracted from the incoming request and is matched with the local in-memory Blacklist database.
If a match is found for the URL in the Blacklist database, the packets are treated as per the blacklisting action
configured—Discard, Redirect, or Terminate flow.
In case of multiple HTTP requests in the same TCP packet, if any of the URLs match the packet is treated as
per the blacklisting action configured.
If a match is not found, the request is allowed to pass through.