<img src="..."> <a href="..."> name</a> ...
http http://servername[:port][/pathname[#html_anchor]][?arguments] ftp nntp ^ argument1&argument2&... spaces given by "%20" mailto telnet defaults ~user -> /home/user/public_html directory -> look for index.html
+-------------------------------------------------------+ | user | +------+------+------+------+------+------+------+------+ | | PING | DHCP | DNS | MIME | SMTP | POP3 | HTTP | | +------+------+------+------+------+------+------+ | ARP | ICMP | UDP | TCP | | +------+-------------+---------------------------+ | | IP | +------+------------------------------------------------+ | local area network | +-------------------------------------------------------+
web client - browser name server web server -------------------- ----------- ---------- (1) DNS query using UDP --> (port 53) <-- DNS response message gives IP address (2) HTTP get using TCP -------------------> (port 80) get <header name> : <header data> <blank line> <------------------- HTTP response message <response line> <response headers> <blank line> <response body> <version> <status code> <message> 200 OK 404 not found
see also
proxy gateway * client side * server side * can serve some requests but * translate protocols rewrites and forwards most * authenticates .-------------------. .-------------------. | client proxy | | gateway server | | .----. .----. | | .----. .----. | | | |---->| |------> ------>| |---->| | | | | |<----| |<------ <------| |---->| | | | `----' `----' | | `----' `----' | `-------------------' `-------------------'
"For example, when a Web surfer connected to an ISP in Boston clicks on a photo of New England Patriots quarterback Tom Brady on CNN.com's Web site, the photo is "pulled" to the Akamai server closest to that user's ISP. Anyone else in the network who subsequently requests Brady's photo gets it from the same cache, rather than CNN's origin server, thus cutting down on bandwidth and eliminating router hops. Meanwhile, infrequently accessed content and content that has passed its "time-to-live" freshness date are regularly flushed out of the network." [http://www.apertura.com.au/articles.html]
CNN.com: Facing A World Crisis William LeFebvre, CNN Internet Technologies Who are we? CNN.com (Turner Broadcasting) - 50 web sites (CNN.com, cartoon network, etc) - 200 servers Network Bandwidth (on 9/11) - 2 OC-12 1,244 Mbps - 7 OC-3 1,085 Mbps - Total 2,329 Mbps Hardware - Standard web server: Sun 420R 4x4 (4 CPU, 4GB RAM) - CNN.com normally used a 15 server pool - Load balancers front-end all web services Typical Loads Peak Total Total Date Hits/min Hits/min Page Views - 9/11/00 220K 148M 11.8M One year prior - 11/8/00 1,217K 722M 139.4M Day after Election Day - 9/10/01 156K 104M 14.4M Day before 11/8/00 was the record page views to date Managing Unexpected Loads - swing servers (move servers from one web service to another) - add additional servers - reduce page complexity (remove advertisements, pictures, text) Reducing Page Complexity - Three page styles (standard, split, ultra light) - Standard - Split (half page with link to more info) - Untra light (minimal information, with links for more info) On the morning of Sept 11, there were 10 servers providing CNN.com. Loads on 9/11-12 Peak Total Total Date Hits/min Hits/min Page Views - 9/10/01 156K 104M 14.4M Day before - 9/11/01 1,110K 411M 132.4M Day of - 9/12/01 948K 797M 304.8M Day after On 9/11, the peak demand was estimated at 1.8M hits per minute, or 20 times normal.
[http://www.dvwebvideo.com/2000/0500/gordon0500.html]
CNN Interactive uses a custom-designed live-capture system that encodes five different streaming media files in a single pass. This is accomplished by taking an analog feed out of the Media 100, then splitting it five ways to separate PCs: two for RealNetworks streams and two for Windows Media at 28kbps and 80kbps data rates. The fifth machine creates an AVI file that's converted separately to QuickTime. All render at a frame size of 176x132 pixels
Security (TBD)
"Phishing is an Internet scam in which unsuspecting users receive official-looking e-mails that attempt to fool them into disclosing online passwords, user names and other personal information. Victims are usually persuaded to click on a link that directs them to a doctored version of an organization's Web site."
Actual example I received as a spam email (slightly edited)
Subject: LaSalle Bank Client Information From: LaSalle BankDate: Mon, 25 Apr 2005 10:22:46 -0400 Dear Customer: We've noticed that you experienced trouble logging into LaSalle Online on 04/24/2005. After three unsuccessful attempts to access your account, your LaSalle Online Profile has been locked. This has been done to secure your accounts and to protect your private information. LaSalle Bank is committed to making sure that your online transactions are secure. You may unlock your profile by going to: <A href="http://211.60.218.225/"> https://lasalle.com/online/unlock_profile.jsp</A> If you're still having trouble, online support is available for you at: <A href="http://211.60.218.225/"> https://lasalle.com/online/support.jsp</A> If you should have any additional questions or concerns, please contact Customer Service at: <A href="mailto:custserv@lasalle.com"> custserv@lasalle.com</A> Thank You for using LaSalle Online ! LaSalle Online Reference Number: 284386
mark@cs.clemson.edu