Agenda Client/Server Model IP Addresses URLs Domain Names READ Zeid: page 3-20

URLs Uniform Resource Locator Human-readable WWW Address Examples: ftp://ftp.cs.rpi.edu Includes addresses and newsgroups

URLs Example: http is the protocol www is the host name (server name) cs.siena.edu is the domain (network address) edu is the top level domain siena is essentially Siena College’s network cs is the CS Dept Network (sub-set of Siena)

WhoIs Search Lets do a Whois Search on some popular domains siena.edu harvard.edu

IP Addresses Numeric Internet Address Part of the TCP/IP Protocol URLs are translated into IP Addresses by DNS Servers DNS  Domain Name System

IP Addresses Example: numbers separated by decimal points 64 is the top level network 4 is a specific computer (host or server) Lets do an nslookup on an IP Address

Client/Server The WWW is huge client/server system with millions of web servers (called hosts) and soon to be billions of clients Web Servers are obviously the servers Web Browsers are the client applications

Other Servers on the Internet Companies also have Database servers that are connected to the Internet some are widely available via URLs and Web- based Interfaces Wanna see my favorite one?

Protocols to remember HTTP HTTPS mailto NNTP (Network News Transfer Protocol) Telnet, SSH, Secure Shell File:

Intranets vs. Extranets What is the difference? What does Siena have? What does the CS Dept. have?

Web Browsers Internet Explorer Netscape Mozilla Opera Why does it matter?

Web Browsers Things that really matter cache 3 rd party toolbars Plug-ins History lists, privacy, security Things everyone should know.

Web Servers Any computer can be a web server CS Server: Compaq Intel Pentium III running an Apache web server for RedHat Linux 7.1 Adequate for about http requests per minute Actually get about 250 request per day Why is the CS website so slow? It depends on where you are?

Web Servers Rough map of the world as seen from our web server Your web is only as fast as your slowest network bottleneck. Ken Swarner’s office www (ares) Roger Bacon Siena College

Web Servers Web servers do NOT have to be dedicated There can be other software Other processes running Other purposes Web servers are often Application servers Database servers Domain name servers Personal computers

Web Servers Powerful servers Multiple processors for handling simultaneous requests Lots of memory (RAM) so files don’t have to be retrieved from slow hard drives RAM is perhaps the most important investment Who has powerful servers Yahoo, Google, Amazon, Ebay, Travelocity Major networks: CNN, ABC, NBC, CBS, etc. (ESPN) Microsoft, IBM, & ??? (Dell???)

Web Servers How can I set up my own web server. 1. First, you need to get software 2. Second, you need a pretty good internet connection 3. Third, you need to register a domain name 4. Finally, you need to actually make some webpages How much does this all cost? How hard is it?

Web server software Apache (its free and its very good) UNIX and Windows versions Problems: Not super easy to setup or configure If you are not already a nerd, you’ll probably need a lot of time. Microsoft makes several different servers Somewhat easier to setup than Apache

Internet connections Dial-up $10-30/month DSL $30-40/month Cable $40-50/month

Internet connections T1 $250 to $1000/month 1-3 Mbps T3 $3000 to $15,000/month 3-45 Mbps

Internet connections OC-3 $20,000 to $50,000/month 150+ Mbps OC-12 Over $500,000 year 600+ Mbps OC-48 Good luck finding one used internally by companies like Sprint who sell the above connections Mbps

Internet Connections Siena used to have 3 dedicated T-1 lines (bundled?) about 3 Mbps Siena now has RoadRunner Premier (perhaps two separate connections) about 6 Mbps (just a guess

Internet Connections RPI (3 years ago) Equivalent of 2 dedicated T-3’s 50+ Mbps 10-times Siena’s bandwidth. Now, they may have an OC Mbps 30-times Siena’s bandwidth

Domain Names Once managed by the InterNIC Internet Network Information Center Non-profit organization of professional Public interest in mind Still manages.org in North America Who manages domains now?

Domain Names The Internet Assigned Numbers Authority (IANA) is the overall authority for the IP Addresses, the Domain Names, and many other parameters, used in the Internet. APNIC (Asia Pacific Network Information Centre) - Asia/Pacific Region APNIC (Asia Pacific Network Information Centre) ARIN (American Registry for Internet Numbers) - North America and Sub-Sahara Africa ARIN (American Registry for Internet Numbers) LACNIC (Latin American and Caribbean IP address Regional Registry) - Latin America and some Caribbean Islands LACNIC (Latin American and Caribbean IP address Regional Registry) RIPE NCC (Réseaux IP Européens) - Europe, the Middle East, Central Asia, and African countries located north of the equator RIPE NCC (Réseaux IP Européens)

Domain Names Many companies act as a 3 rd (and even 4 th ) party and will register your domain name with the proper authorities. The InterNIC itself acts as a 3 rd party in registering many domain names. Registering a domain just reserves the name.

Spoofing Ultimately, Domain name servers determine Which domain names are associated with which hosts. Remind me to tell you a story.

Domain Names

To get the Internet to recognize your domain you have to get your ISP to add your domain to its Domain Name Server This will have a cascading effect and eventually your domain can be reached. My computer IP Address: ISP Domain Name Table …  … DNS Authority

Multi-tiered

Domain Names & Hosting Companies that register your domain name are often ISP’s and Will set you up with: A domain name A dedicated IP address And, they make sure you get added to the right tables Associates your IP address with your domain.

On-site vs. Off-site Most hosting companies have their own servers and will provide off-site hosting Off-site means they host your stuff on their servers You don’t have your own servers on-site Most ISP can set you up on-site if you have Your own server Your own support personal Your own infrastructure

Other hosting options Free services Angelfire Geocities Cheap services Roadrunner AOL Piggy-backing College Company