Using Quality of Service
222
Netscape Enterprise Server Administrator’s Guide • November 2001
❍
If chunked encoding is enabled in either or both directions, the chunking
layer removes the chunk headers and they are not counted in the traffic.
Other headers or protocol items are counted.
•
The quality of service features cannot accurately measure traffic from
PR_TransmitFile
calls. For basic I/O operations such as
PR_Send()/net_write
or
PR_Recv()/net_read
, the data transferred can be
quickly accounted for by the bandwidth manager, since the number of bytes
transferred in one system call is usually the size of a buffer and the I/O call
returns quickly. This works very well to measure the instantaneous bandwidth
of dynamic content applications. However, because the amount of data
transferred from
PR_TransmitFile
is only known at the end of the transfer, it
can’t be measured before it completes.
If the
PR_TransmitFile
is short, then the quality of service features will
perform adequately. However, If the
PR_TransmitFile
is long, such as in the
case of a long file downloaded by a dialup user, the whole amount of data
transferred will be counted at completion time. When the bandwidth manager
recomputes bandwidth after the next recompute interval period starts, the
bandwidth computed will go up significantly because of that recent large
PR_TransmitFile
. This case could cause the server to deny all requests until
the next metric interval, when the bandwidth manager will "expire" the
transmit file operation, since it is too old, and thus the bandwidth value will go
back down. If your site has a lot of very long static file downloads , the you
should increase the metric interval from the default 30 seconds.
•
The bandwidth computed is always an approximation because it is not
measured instantaneously, but is recomputed at regular intervals and over a
certain period. For example, if the metric interval is the default 30 seconds and
the server is idle for 29 seconds, then the next second, a client could potentially
use 30 times the bandwidth limit in one second.
•
The quality of service bandwidth statistics are lost whenever the server is
reconfigured dynamically. In addition, the quality of service limitations are not
enforced in threads that have connections on an older, inactive configuration,
because the bandwidth manager thread only computes bandwidth statistics for
the active configuration. Potentially, a client that doesn’t close its socket for a
long time and remains active so that the server doesn’t time it out would not be
subject to the quality of service limitations after a server dynamic
reconfiguration.
Summary of Contents for NETSCAPE ENTREPRISE SERVER 6.0 - ADMINISTRATOR
Page 1: ...Administrator s Guide Netscape Enterprise Server Version6 0 November 2001...
Page 18: ...18 Netscape Enterprise Server Administrator s Guide November 2001...
Page 26: ...26 Netscape Enterprise Server Administrator s Guide November 2001...
Page 48: ...Migrating a Server 48 Netscape Enterprise Server Administrator s Guide November 2001...
Page 50: ...50 Netscape Enterprise Server Administrator s Guide November 2001...
Page 146: ...146 Netscape Enterprise Server Administrator s Guide November 2001...
Page 242: ...242 Netscape Enterprise Server Administrator s Guide November 2001...
Page 294: ...294 Netscape Enterprise Server Administrator s Guide November 2001...
Page 332: ...Deleting a Virtual Server 332 Netscape Enterprise Server Administrator s Guide November 2001...
Page 378: ...378 Netscape Enterprise Server Administrator s Guide November 2001...
Page 396: ...Responses 396 Netscape Enterprise Server Administrator s Guide November 2001...
Page 414: ...Posting to JSPs 414 Netscape Enterprise Server Administrator s Guide November 2001...
Page 432: ...Further Information 432 Netscape Enterprise Server Administrator s Guide November 2001...
Page 444: ...444 Netscape Enterprise Server Administrator s Guide November 2001...
