Cisco Cisco Web Security Appliance S170 사용자 가이드

If the connection between the FTP Proxy and the FTP server is slow, uploading a large file may take a long 
time, particularly when Cisco Data Security Filters are enabled. This can cause the FTP client to time out 
before the FTP Proxy uploads the entire file and you may get a failed transaction notice. The transaction 
does not fail, however, but continues in the background and will be completed by the FTP Proxy.

You can workaround this issue by increasing the appropriate idle timeout value on the FTP client.

FTP clients create a zero byte file on FTP servers when the FTP Proxy blocks an upload due to outbound 
anti-malware scanning.

Chrome browsers do not include a user-agent string in FTP-over-HTTP requests; therefore, Chrome 
cannot be detected as the user agent in those requests.  

The WSA is designed to handle thousands of client and server connections in parallel, and the sizes of 
the send and receive buffers are configured to deliver optimal performance, without sacrificing stability. 
Generally, actual usage is browse traffic, consisting of numerous short-lived connections for which we 
have receive-packet-steering (RPS) and receive-flow-steering (RFS) data, and for which the WSA has 
been optimized.

However, at times you may experience a noticeable reduction in upload or download speeds; for 
example, when transferring large files via proxy. To illustrate: assuming a 10-Mbps line, downloading a 
100-MB file that passes through a WSA can be approximately seven to eight times slower than 
downloading the file directly from its server.

In non-typical environments that include a larger proportion of large-file transfers, you can use the 

networktuning

 command to increase send and receive buffer size to alleviate this issue, but doing so can 

also cause network memory exhaustion and affect system stability. See 

 for details of the 

networktuning

 command. 

Exercise care when changing the TCP receive and send buffer control points and other TCP buffer 
parameters. Use the 

networktuning 

command only if you understand the ramifications.

Here are examples of using the 

networktuning

 command on two different appliances:

networktuning 

sendspace = 131072

recvspace = 131072

send-auto = 1 [Remember to disable miscellaneous > advancedproxy > send buf auto tuning]

recv-auto = 1 [Remember to disable miscellaneous > advancedproxy > recv buf auto tuning]

mbuf clusters = 98304 * (X/Y)  where is X is RAM in GBs on the system and Y is 4GB.

sendbuf-max = 1048576

recvbuf-max = 1048576