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• Redirections - Often an embedded image or
even an HTML page is actually available
from a different web server than the one from
which it is originally requested. A web server
may instruct the browser to retrieve a URL
from another web page with a redirection. A
redirection may be accomplished either with
an HTTP 301 or 302 response or with
HTML. The use of redirection increases
response time by requiring URL retrieval to
obtain the redirection followed by another
URL retrieval to actually obtain the URL.
6 TYPICAL WEB PAGE
RESPONSE ANALYSIS
A simple table-based simulation of a web browser
(see Table 5) reveals that the typical secure web
page discussed is retrieved in no less than 16 round-
trips even under the following set of reasonably
optimistic assumptions:
• Broadband connection – i.e. the time to
actually transmit packets and browser and server
processing time are negligible compared to the
response time contributed by the number of round
trips required to paint the page.
• The browser permits up to a maximum of 16
simultaneous HTTPS connections to a given SSL
server. The default value for this is for most
browsers is 4 connections to HTTP 1.0 and 2
connections for HTTP 1.1. Assuming this is
optimistic in that changing this configuration is for
experts only in that it involves editing the windows
registry, javscript files or something similarly for
experts only.
• Use of persistent connections. This is enabled
by default for most modern browsers and is
supported in many cases by secure web servers.
• No persistent connections exist when the web
page retrieval begins.
• Use of SSL session reuse. This is enabled by
default for most modern browsers and servers.
• The DNS lookup for the main server does not
cost a round-trip, although a DNS lookup for a
redirected image’s server does cost a round trip.
• Once a URL is assigned to a connection, it
uses that connection even if it has to wait for the
connection to be established.
• No HTTP pipelining. This paper’s analysis of
web page response time does not assume the use of
HTTP pipelining because no popular browser has
this enabled by default. This is probably due to flaws
in the pipelining protocol design and server
implementations thereof.
As can be seen in table 3, while round-trip time
is a major contributor to response time for intercity
broadband connectivity (much less so for LAN
connectivity), it completely dominates
intercontinental Internet and satellite network
response time. This problem is significant enough
for non-satellite networks that at least one Internet
Startup, www.netli.com, is introducing a global
distributed caching solution that advertises 1 sec
secure web browsing to enterprise Intranet servers.
7 BROWSER
RECOMMENDATIONS
Each of the following recommendations mitigates an
inefficiency that applies especially to secure web
browsing. The recommendations are as follows:
1. Connection Pooling – reduces the response
time impact of SSL connection establishment
whether the server supports persistent connections or
not. Connection pooling establishes and maintains a
pool of connections with a secure server so that an
established connection can be allocated to the
retrieval of a URL as soon as the need to retrieve it
is determined. The recommended connection
pooling maintains a historical record of the number
Table 3: Round-Trip Time Impact on Secure Web Page Response Time
Network Type
Pin
Response
Time (Sec)
Typical
Secure Web
Page
Response
Time (Sec)
Percentage of Response
Time Due to Round Trips
With .25 Sec Server Response
Time
Fixed Assignment Satellite Network 0.650 10.4 98%
Demand Assigned Satellite Network 1.300 20.8 99%
East Coast USA to India via Internet 0.300 4.8 95%
East Coast USA to Moscow via Internet 0.180 2.88 92%
Washington DC to New York 0.030 0.48 66%
Local Area Network 0.001 0.016 6%
SECURE WEB BROWSING OVER LONG-DELAY BROADBAND NETWORKS - Recommendations for Web
Browsers
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