Web Fendamentals

Server Fundamentals 1

Building and Managing Web Sites with Microsoft Technologies

Web Server Fundamentals


Server Fundamentals• Software that answers requests for files,

printing, communications, etc.• Server software normally accessed by many

different users via a network.• Server software normally run on a

dedicated computer (“box”).• The “Box” is often called a server as well.• Server boxes typically more powerful than

workstations.


Web Server FundamentalsA webserver is software that does the following:• Server receives requests from browser/client for resources– A resource is any chunk of information that can be

identified by a URL like HMTL or image files, scripts, streaming media, etc.

• Server retrieves and/or processes the resource• Server sends the resource back to the client• Server logs the transaction• Responses/requests occur using the HTTP

protocol, typically on port 80


Sample HTTP ExchangeTo retrieve the resource at http://www.host.com/path/file.html

Browser sends request to host www.host.com, port 80: GET /path/file.html HTTP/1.0From: [email protected]: Mozilla/4.01

The server sends a response back to the client: HTTP/1.0 200 OKDate: Fri, 31 Dec 1999 23:59:59 GMTContent-Type: text/htmlContent-Length: 1354<html><body><h1>Happy New Millenium!</h1>(more file contents) </body></html>


Response Status Line• Includes three parts separated by spaces

– the HTTP version– a response status code that gives the result of the

request– An English reason phrase describing the status code.

• Typical status lines are:HTTP/1.0 200 OK or HTTP/1.0 404 Not Found


Common Response Status Codes• 200 OK - Request succeeded, resulting resource is

returned in the message body• 404 Not Found --The requested resource doesn't exist.• 301 Moved Permanently • 302 Moved Temporarily • 303 See Other (HTTP 1.1 only) Resource has moved to

another URL (given by the Location: response header), and should be automatically retrieved by the client.

• 500 Server Error -- Unexpected server error. Common caused by a server-side script that has bad syntax, fails, or otherwise can't run correctly.


Response “Content-Type”

• Response header includes “Content-Type” to tell client/browser how to handle the resource (display a browser or launch an application/plug-in)

• Based on MIME types for email attachments• Broad types: text, image, audio, video, application• Many different subtypes, always new ones.• E.g., Content-Type: text/html• Most webservers software have a list of common

types – must define new subtypes on webserver


Web Server Fundamentals

• Webservers process response/requests, log activity, and handle scripts.

• Personal Web Server a good example.• BUT -- Life gets complicated when…

– Additional services are desired (FTP, Listservers, NNTP, Streaming Media, etc.)

– Server-side dynamic content can quickly overwhelm a server “box”


Establishing a Web Presence

• Different paths for different needs:– Develop a small local webserver (PWS).– Use space provided by your ISP.– Lease space with a web hosting service.– Lease a server with a web hosting service.– Create and manage your own webserver.– Create and manage a webserver farm.


Key Considerations (1)• Web site goals and architecture

– Static vs. dynamic content– Internet vs. Intranet vs. Extranet– Domain name required?– Special technologies needed for some resources (e.g.,

streaming media, secure e-commerce)?• Resources (Time, money, and expertise)

A balance between:– How much can you spend (including personnel)?– How much time and expertise do/can you have?


Key Considerations (2)• Site Usage

– How much traffic initially and in future?– Secure access required for some/all of content?

• Control and Accountability– What level of service/support is acceptable?– Who gets the blame?

• Technology– Are specific platforms/technologies required (e.g., Unix

vs. NT, FrontPage Server Extensions)?


Develop a small webserver• Use Personal Web Server or other

free/inexpensive webserver software locally.• Can use nearly any type of computer.• Typically used only for very small Intranets (10-

50 users) or development purposes.• Low or no cost.• Limited number of connections possible.• Limited capabilities and reliability.


Using your ISP• Many ISPs offer space on their webservers (e.g.,

http://www.mother.com/~callen/ )• Typically access pages via FTP.• Minimal or no cost.• Most ISPs provide few capabilities (limited

dynamic content, no FrontPage Extensions, etc.)• Limited reliability and support – not a primary

business activity for ISPs.• No domain name gives less professional

impression.


Using a “free” service

• Other sites offer free web sites• Typically must include advertisements or

other promotions in your web pages• Limited disk space• Example:

– Geocities (www.geocities.com)• Check out http://www.freewebspace.net/

http://www.geocities.com/


Web hosting services – Leasing space

• Many companies specialize in providing equipment and services to “host” your web site.

• They set up multiple “virtual webservers” on their webservers.

• Server and maintenance costs spread among many users.• Most services will handle registering your domain.• Typical monthly costs (comparison difficult):

– Bare bones $10-20– FrontPage Extensions, ASP, etc. $25-35– Small/medium e-commerce site, $35-65


Web hosting services - Advantages

• Low entry cost• Service monitors your virtual server: 24 hours,

365 days/yr.• Most offer multiple links to the Internet backbone.• Most services claim/offer high uptime (98%+).• Service manages hardware and server

maintenance.


Web hosting services – Disadvantages• Sharing server causes less reliable response times.• Quality, support, and professionalism vary widely.• Very competitive -- some go under.• Very difficult to compare prices.• Hassles moving from one service to another.


Web hosting services - Leased servers• Typically have expensive multiple, redundant

connections to Internet.• Control of your server through Root or

Administrator access. Typically connect using PC Anywhere or similar software.

• Services typically offer uninterruptible power supply and generator back-ups.

• Typical monthly costs:• $200-1000 depending on machine and features.


Web hosting services – Shopping hints• Define everything you must have before

you shop (FP Extensions, ASP, Index Server, CGI, etc.)

• Use Hosting Service pages to identify good prospects:– http://www.hostsearch.com/– http://www.webhosters.com/


Web hosting services – Shopping hints• Compare services/prices carefully.

– You get what you pay for – if it sounds too good to be true, it is!

– Look for at 20MB of disk space for growth.– Be careful of bandwidth – look for 1GB monthly

minimum.– Ask for specific on SSL implementations.– Domain registration should be free (although InterNIC

will charge you $70 for two years registration)• Ask for a list of sites they are currently hosting.

– Check periodically for availability/response.– E-mail webmaster for a quick comment of the service


STOP AND THINK HARD!

• Before you think about managing your own webserver, explore all outsourcing options.

• Managing your own webserver is resource intensive.

• Don’t do it unless you need very high control/accountability, extreme reliability, or special technologies.

• Outsourcing is getting better and better…


What you need for your webserver• Staff

– Knowledgeable and/or trainable staff in web management

• Connectivity– A dependable connection to the Internet.

• Server– A server box(s) for your webserver software and web

content.• Webserver software

– Software to handle HTTP requests for resources.


Staffing• Training takes time – Expertise takes longer!

– Start small and build up…• Hiring experts in-house takes time and is difficult.

– Limited pool of experts• Contractors are costly…

– You will spend much time working with and managing your contractors.

– If use contractors, try to have contractors train your in-house staff.


Connecting to the Internet (1)• Dial-up or Dedicated Phone Line

– Use an analog modem (up to 56 kbps) via the PSTN (Public Switched Telephone Network)

– Low-cost, available everywhere, slow, analog/digital translation introduces problems, long-connection time, not scalable

• ISDN (Integrated Services Digital Network)– Connections between 64-128 kbps.– Pretty good cost/value, pretty good availability (uses

existing lines), continuous connection possible, limited scalability


Connecting to the Internet (2)• DSL/ADSL – Digital Subscriber Lines

• Provides a dedicated digital circuit between a residence and a telephone company's central office

• A is for asynchronous – different speeds coming in and going out – not ideal for a busy webserver.

• Current typical speeds of 1.5 MBPS downstream and 384 KBPS upstream (or 384/128 KBPS).

• Must be located within about 17,500 feet of their central telephone switching office.

• Costs in flux – $35-200/month• Good value, continuous connection, limited scalability


Connecting to the Internet (3)• Digital Data Service (DDS)

– Lease a digital line from a ISP or Telco.– Requires a dedicated line and some type of unit

(Channel Service Unit/Data Service Unit) for converting signals & protecting provider’s network

– Available in many forms: fractional T1, T1, T3, etc. – Most common connections at:

• DS1/T1 – 1.544 mbps• Fractional DS1/T1 available in 64 kbps increments• DS3/T3 – 44.736 mbps (typically used by ISPs)

– Typical costs: $1000/month plus ISP costs


Setting up a Server• General considerations

– Avoid future problems and costs by purchasing off-the-shelf, name-brand systems and components.

– Purchase as much machine (“more power!”) as you can afford.

– Purchase a service agreement.– Locate server in clean, cool, dry location.– Make sure the equipment you buy will work with the

operating system.• For NT, see: http://www.microsoft.com/isapi/hwtest/hcl.idc


Basic Server Security

• Server “box” should be in a physically secure location.

• Webservers should be located carefully on LANs.– Webservers located within a LAN should not be

located on busy network segments.– Routers can filter inappropriate packets.– Firewall software/hardware can be used to screen

traffic more carefully.– Ideally, Internet servers should be outside LAN.


Server Operating Systems• Windows NT Server

– GUI orientation– Lower entry cost…– Mass market appeal– Integrated with other Microsoft products

• Unix - Solaris/HP-UX/AIX/SCO/s5r4– Not cheap– Well supported– Additional web server required (most of the time)

• Unix – Linux/FreeBSD– Cheap– Support issues– Includes Apache webserver, most popular in the world


Server CPU• Buy as much as you can -- stay behind leading

edge.• Static content requires considerably less CPU than

dynamic content.• Consider whether dynamic content can be

presented/converted into static content.• Partition dynamic content onto separate servers to

increase performance.• Server with average CPU load of >60% needs

upgrading.


Server Memory• The most critical portion of a webserver.• Don’t skimp. Buy as much as you can afford!• Commonly used resources (e.g., web pages) are

cached in memory.• Many webservers run multiple services, each which

require memory.• Consider your memory upgrade path.• For Windows NT webservers:

– 128 MB is bare bones– 256 MB is a good entry point– Rumor: Windows 2000 happy at 512MB


Server Hard Disks• 3-5% chance of failing over a 3 year period.• SCSI better (but more expensive) than ATA/IDE.

– Typically better throughput.– Multiple drives can be active simultaneously.– Supports RAID arrays. (see next slide)

• Better to have multiple disks – o/s and services on one– data on additional disks

• Isolate differing parts of a site on different volumes• Particularly place data on a different “spindle” then you FTP

content or web pages


RAID Arrays• RAID (Redundant Array of Independent Disks)

joins several disks together to increase performance and fault tolerance.

• RAID 1 or 5 is usually the best choice for a Web server.

• RAID 1 (disk mirroring): data written to redundantly to two separate hard drives working together.

– Should one drive fail, the others can take over automatically.• RAID 5 (Striped Volume Sets)

– Even higher reliability across multiple volumes. Can be “hot swapped”.


Other Server Features

• CD-ROM• Use a quality (expensive) network interface

card (NIC), which unburdens CPU.• Quality SCSI/disk controller card• Back-up technologies

– Tape– Optical media– CDR and CD/RW


Configuring NT Server as a webserver• Boot drive should be NTFS for security.• Swap file should be on a separate physical disk

from the operating system.• FTP Server should be on its own partition to avoid

filling attacks that fill up drive.• Optimize o/s for server operation.• Disable unnecessary services.• Avoid loading unnecessary network protocols.• If have multiple web servers, configure them the

same for simpler maintenance.


Webserver Software

Top placed servers in March 1999Source: http://www.netcraft.com/survey

Apache2,409,056 54.89%Microsoft-IIS 1,030,892 23.49%Netscape Enterprise 205,645 4.69%RapidSite 85,076 1.94%WebSite Pro 78,515 1.79%

Web Fendamentals

Software

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