ENGS 112

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ENGS 112 Lecture 2 HTML Primer See text or web
for more information and examples.
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HTML is HyperTex Markup Language HTML is a
specialization of SGML HTML is a language for
describing how web pages should look. HTML has
some constructions for forms, frames, etc that
make it a bit more dynamic. HTML is very
simple....were going to go over only the
basics...other sources - Dietel - read the
source of other pages - web HTML manuals and
how-tos
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Basic syntax of an HTML construct

• HTML uses tags
• tags typically have a beginning and a closing
  version.
• example....every html page should start with the
  tag
• lthtmlgt
• and end with
• lt/htmlgt
• Not essential but good style.

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Basic structure of an HTML page
lthtmlgt ltheadgt lttitlegt Our first
page!! lt/titlegt lt/headgt ltbodygt Blah, blah,
blah lt/bodygt lt/htmlgt
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Some tags
Headings lth1gt...lt/h1gt, lth2gt.....lt/h2gt,.... New
paragraph ltpgt Line Break ltbrgt Horizontal
rule lthrulegt Lets try them now....
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Links and URLs
Web link construction lta hrefhttp//www.cnn.com
gtCNNs web sitelt/agt ltagt lt/agt HTML anchor
tag http// is the protocol or
scheme www.cnn.com is the server name anything
following that is the path name CNNs web site
is the anchor
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Absolute and relative links
lta hrefhttp//www.dartmouth.edu/gvc/gtDartmouth
lt/agt is an absolute reference to a web page. lta
hrefsomefile.htmlgt Another linklt/agt is a
relative link.
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Text properties
ltbgt lt/bgt boldface ltigt lt/igt
italics ltblinkgt lt/blinkgt blinking ltugt
lt/ugt underlining ltstrikegt lt/strikegt striked
out
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Backgrounds
ltbody bgcolorrrggbbgt OR ltbody
backgroundsome url or relative file
namegt Where can you get some fun
backgrounds? Lets do some searches!!!!
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Adding images
Image formats most browsers can view jpeg, jpg
Joint Picture Experts Group tif gif .....et
c ltimg srcsome URL or filename altpicturegt
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Images as anchors for links
lta hrefURLgtltimg srcULRgtlt/agt Lets do an
example......
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URLs and Internet Names, addresses, etc
www.dartmouth.edu is the name of a server The
name is for human consumption...the internet uses
a four number address to identify all hosts on
the internet. 129.170.16.79 Each number is
between 0 and 255.
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Lets buy an internet domain name!!!
Visit www.nsi.com to see what names are taken,
who owns a particular name, or buy a name for
yourself!!!
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Domain names are hot commodities....ebay auction
Name brands and common words are all taken. All
two and three letter combinations are gone. This
is the real estate of cyberspace!!!
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Networked Services
Applications WWW Streaming data audio and
video Internet telephony and videoconferences Ne
tworked games Client/server Sensor
networks Broadcast TV video on demand
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Quality of Service (QoS)
Constant bit rate (CBR) Variable bit rate
(VBR) End-to-end delays, latency Bit error
rates Admission policy and blocking probabilities
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Engineering Challenges of Different Content Types
Content
Bandwidth Bursty QoS?
Web, data Medium Yes
No
Voice Low Yes
Yes
TV, video High No
Yes
Monitoring Variable No
No
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Network Elements
Links and switches abstractions as graphs and
queues Service characterizations total delay
trans prop qd proc
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Network Mechanisms
Multiplexing sharing a common
channel/resource Time-division multiple access
TDMA Statistical multiplexing Spatial
multiplexing Frequency-division multiple
access Code-division multiple access
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Network Mechanisms
Switching circuit switching packet
switching datagram network vs virtual
circuit switch design Clos and other switch
designs
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Packet Switching
Send packets into the network, routing each
packet individually, like the post office.
Packets are routed through the network, sorted
at switches. Requires no setup time but no
guarantee of service!!
Good for telephones, bad for web browsing!!!!
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Network Mechanisms
Error control - detection vs
correction parity bits cyclic redundancy
codes replication for error correction BCH
and Reed-Solomon codes error detection and
correction protocols retransmission protocols
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Network Mechanisms
Flow control Congestion control problems with
long haul, high speed networks rate control
(open loop) Resource allocation
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Why is convergence achallenge?
Convergence of entertainment, telecommunications
and computing industries. Telecom is set up for
voice. Entertainment requiries audio and video
QoS. Computer communication is based on packet
switching.
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OEE (Due Friday, April 14)
Walrand page 93 1. 3. 4. 12. 16. 20. 25.