TCP/IP Architecture & HTTP Communication: Network Layers, DNS, & Server Log Analysis, Slides of Fundamentals of E-Commerce

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TCP/IP Layering Architecture

• A simplified model, provides the end-to-end

reliable connection

• The network layer

–

Hosts drop packages into this layer, layer routestowards destination

Only promise “Try my best”

• The transport layer

–

Reliable byte-oriented stream

Hypertext Transfer Protocol (HTTP)

• A connection-oriented protocol (TCP) used to

carry WWW traffic between a browser and aserver

• One of the transport layer protocol supported

by Internet

• HTTP communication is established via a TCP

connection and server port 80

GET Method in HTTP

Domain Name System

•^

DNS (domain name service): mapping from domainnames to IP address

-^

IPv4:

• IPv4 was initially deployed January 1

st. 1983 and is

still the most commonly used version.

• 32 bit address, a string of 4 decimal numbers

separated by dot, range from 0.0.0.0 to255.255.255.255.

-^

IPv6:

• Revision of IPv4 with 128 bit address

Top Level Domains (TLD)

•^

Top level domain names, .com, .edu, .gov and ISO3166 country codes

-^

There are three types of top-level domains:

-^

Generic domains

were created for use by the Internet public

-^

Country code

domains were created to be used by individual

country

-^

The .arpa domain

A

ddress and

R

outing

P

arameter

A

rea

domain is designated to be used exclusively for Internet-infrastructure purposes

Registrars

• Domain names ending with .aero, .biz, .com,

.coop, .info, .museum, .name, .net, .org, or.pro can be registered through many differentcompanies (known as "registrars") thatcompete with one another

• InterNIC at

http://internic.net

• Registrars Directory:

http://www.internic.net/regist.html

Server Log Files

•^

Server Transfer Log: transactions between a browserand server are logged

-^

IP address, the time of the request

-^

Method of the request (GET, HEAD, POST…)

-^

Status code, a response from the server

-^

Size in byte of the transaction

-^

Referrer Log: w

here the request originated

•^

Agent Log:

browser software making the request (spider)

•^

Error Log:

request resulted in errors (404)

Server Log Analysis

• Most and least visited web pages• Entry and exit pages• Referrals from other sites or search engines• What are the searched keywords• How many clicks/page views a page received• Error reports, like broken links

Server Log Analysis

Search Engines

-^

According to

Pew Internet Project

Report

(2002), search engines are the most popularway to locate information online

• About 33 million U.S. Internet users query on

search engines on a typical day.

• More than 80% have used search engines •^

Search Engines are measured by coverage andrecency

Coverage

-^

Overlap analysis

used for estimating the size

of the indexable web

• W: set of webpages• Wa, Wb: pages crawled by two independent engines

a and b

• P(Wa), P(Wb): probabilities that a page was crawled

by a or b

P(Wa)=|Wa| / |W|

P(Wb)=|Wb| / |W|