data communications

IS 376IS 376 IS 376IS 376 Data Communications Data Communications TechnologyTechnology

Data Communications Data Communications TechnologyTechnology

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Data Communications Data Communications TechnologyTechnologyModern Modern

communicatiocommunication networks n networks carry digital carry digital data, from data, from text, using text, using

ASCII ASCII coding…coding…

Modern Modern communicatiocommunicatio

n networks n networks carry digital carry digital data, from data, from text, using text, using

ASCII ASCII coding…coding…

0000000 NUL (null) 0100000 SPACE 1000000 @ 1100000 `0000000 NUL (null) 0100000 SPACE 1000000 @ 1100000 `0000001 SOH (start of heading) 0100001 ! 1000001 A 1100001 a0000001 SOH (start of heading) 0100001 ! 1000001 A 1100001 a0000010 STX (start of text) 0100010 " 1000010 B 1100010 b0000010 STX (start of text) 0100010 " 1000010 B 1100010 b0000011 ETX (end of text) 0100011 # 1000011 C 1100011 c0000011 ETX (end of text) 0100011 # 1000011 C 1100011 c0000100 EOT (end of transmission) 0100100 $ 1000100 D 1100100 d0000100 EOT (end of transmission) 0100100 $ 1000100 D 1100100 d0000101 ENQ (enquiry) 0100101 % 1000101 E 1100101 e0000101 ENQ (enquiry) 0100101 % 1000101 E 1100101 e0000110 ACK (acknowledge) 0100110 & 1000110 F 1100110 f0000110 ACK (acknowledge) 0100110 & 1000110 F 1100110 f0000111 BEL (bell) 0100111 ' 1000111 G 1100111 g0000111 BEL (bell) 0100111 ' 1000111 G 1100111 g0001000 BS (backspace) 0101000 ( 1001000 H 1101000 h0001000 BS (backspace) 0101000 ( 1001000 H 1101000 h0001001 TAB (horizontal tab) 0101001 ) 1001001 I 1101001 i0001001 TAB (horizontal tab) 0101001 ) 1001001 I 1101001 i0001010 LF (NL line feed, new line) 0101010 * 1001010 J 1101010 j0001010 LF (NL line feed, new line) 0101010 * 1001010 J 1101010 j0001011 VT (vertical tab) 0101011 + 1001011 K 1101011 k0001011 VT (vertical tab) 0101011 + 1001011 K 1101011 k0001100 FF (NP form feed, new page) 0101100 , 1001100 L 1101100 l0001100 FF (NP form feed, new page) 0101100 , 1001100 L 1101100 l0001101 CR (carriage return) 0101101 - 1001101 M 1101101 m0001101 CR (carriage return) 0101101 - 1001101 M 1101101 m0001110 SO (shift out) 0101110 . 1001110 N 1101110 n0001110 SO (shift out) 0101110 . 1001110 N 1101110 n0001111 SI (shift in) 0101111 / 1001111 O 1101111 o0001111 SI (shift in) 0101111 / 1001111 O 1101111 o0010000 DLE (data link escape) 0110000 0 1010000 P 1110000 p0010000 DLE (data link escape) 0110000 0 1010000 P 1110000 p0010001 DC1 (device control 1) 0110001 1 1010001 Q 1110001 q0010001 DC1 (device control 1) 0110001 1 1010001 Q 1110001 q0010010 DC2 (device control 2) 0110010 2 1010010 R 1110010 r0010010 DC2 (device control 2) 0110010 2 1010010 R 1110010 r0010011 DC3 (device control 3) 0110011 3 1010011 S 1110011 s0010011 DC3 (device control 3) 0110011 3 1010011 S 1110011 s0010100 DC4 (device control 4) 0110100 4 1010100 T 1110100 t0010100 DC4 (device control 4) 0110100 4 1010100 T 1110100 t0010101 NAK (negative acknowledge) 0110101 5 1010101 U 1110101 u0010101 NAK (negative acknowledge) 0110101 5 1010101 U 1110101 u0010110 SYN (synchronous idle) 0110110 6 1010110 V 1110110 v0010110 SYN (synchronous idle) 0110110 6 1010110 V 1110110 v0010111 ETB (end of trans. block) 0110111 7 1010111 W 1110111 w0010111 ETB (end of trans. block) 0110111 7 1010111 W 1110111 w0011000 CAN (cancel) 0111000 8 1011000 X 1111000 x0011000 CAN (cancel) 0111000 8 1011000 X 1111000 x0011001 EM (end of medium) 0111001 9 1011001 Y 1111001 y0011001 EM (end of medium) 0111001 9 1011001 Y 1111001 y0011010 SUB (substitute) 0111010 : 1011010 Z 1111010 z0011010 SUB (substitute) 0111010 : 1011010 Z 1111010 z0011011 ESC (escape) 0111011 ; 1011011 [ 1111011 {0011011 ESC (escape) 0111011 ; 1011011 [ 1111011 {0011100 FS (file separator) 0111100 < 1011100 \ 1111100 |0011100 FS (file separator) 0111100 < 1011100 \ 1111100 |0011101 GS (group separator) 0111101 = 1011101 ] 1111101}0011101 GS (group separator) 0111101 = 1011101 ] 1111101}0011110 RS (record separator) 0111110 > 1011110 ^ 1111110 ~0011110 RS (record separator) 0111110 > 1011110 ^ 1111110 ~0011111 US (unit separator) 0111111 ? 1011111 _ 1111111 DEL0011111 US (unit separator) 0111111 ? 1011111 _ 1111111 DEL

0000000 NUL (null) 0100000 SPACE 1000000 @ 1100000 `0000000 NUL (null) 0100000 SPACE 1000000 @ 1100000 `0000001 SOH (start of heading) 0100001 ! 1000001 A 1100001 a0000001 SOH (start of heading) 0100001 ! 1000001 A 1100001 a0000010 STX (start of text) 0100010 " 1000010 B 1100010 b0000010 STX (start of text) 0100010 " 1000010 B 1100010 b0000011 ETX (end of text) 0100011 # 1000011 C 1100011 c0000011 ETX (end of text) 0100011 # 1000011 C 1100011 c0000100 EOT (end of transmission) 0100100 $ 1000100 D 1100100 d0000100 EOT (end of transmission) 0100100 $ 1000100 D 1100100 d0000101 ENQ (enquiry) 0100101 % 1000101 E 1100101 e0000101 ENQ (enquiry) 0100101 % 1000101 E 1100101 e0000110 ACK (acknowledge) 0100110 & 1000110 F 1100110 f0000110 ACK (acknowledge) 0100110 & 1000110 F 1100110 f0000111 BEL (bell) 0100111 ' 1000111 G 1100111 g0000111 BEL (bell) 0100111 ' 1000111 G 1100111 g0001000 BS (backspace) 0101000 ( 1001000 H 1101000 h0001000 BS (backspace) 0101000 ( 1001000 H 1101000 h0001001 TAB (horizontal tab) 0101001 ) 1001001 I 1101001 i0001001 TAB (horizontal tab) 0101001 ) 1001001 I 1101001 i0001010 LF (NL line feed, new line) 0101010 * 1001010 J 1101010 j0001010 LF (NL line feed, new line) 0101010 * 1001010 J 1101010 j0001011 VT (vertical tab) 0101011 + 1001011 K 1101011 k0001011 VT (vertical tab) 0101011 + 1001011 K 1101011 k0001100 FF (NP form feed, new page) 0101100 , 1001100 L 1101100 l0001100 FF (NP form feed, new page) 0101100 , 1001100 L 1101100 l0001101 CR (carriage return) 0101101 - 1001101 M 1101101 m0001101 CR (carriage return) 0101101 - 1001101 M 1101101 m0001110 SO (shift out) 0101110 . 1001110 N 1101110 n0001110 SO (shift out) 0101110 . 1001110 N 1101110 n0001111 SI (shift in) 0101111 / 1001111 O 1101111 o0001111 SI (shift in) 0101111 / 1001111 O 1101111 o0010000 DLE (data link escape) 0110000 0 1010000 P 1110000 p0010000 DLE (data link escape) 0110000 0 1010000 P 1110000 p0010001 DC1 (device control 1) 0110001 1 1010001 Q 1110001 q0010001 DC1 (device control 1) 0110001 1 1010001 Q 1110001 q0010010 DC2 (device control 2) 0110010 2 1010010 R 1110010 r0010010 DC2 (device control 2) 0110010 2 1010010 R 1110010 r0010011 DC3 (device control 3) 0110011 3 1010011 S 1110011 s0010011 DC3 (device control 3) 0110011 3 1010011 S 1110011 s0010100 DC4 (device control 4) 0110100 4 1010100 T 1110100 t0010100 DC4 (device control 4) 0110100 4 1010100 T 1110100 t0010101 NAK (negative acknowledge) 0110101 5 1010101 U 1110101 u0010101 NAK (negative acknowledge) 0110101 5 1010101 U 1110101 u0010110 SYN (synchronous idle) 0110110 6 1010110 V 1110110 v0010110 SYN (synchronous idle) 0110110 6 1010110 V 1110110 v0010111 ETB (end of trans. block) 0110111 7 1010111 W 1110111 w0010111 ETB (end of trans. block) 0110111 7 1010111 W 1110111 w0011000 CAN (cancel) 0111000 8 1011000 X 1111000 x0011000 CAN (cancel) 0111000 8 1011000 X 1111000 x0011001 EM (end of medium) 0111001 9 1011001 Y 1111001 y0011001 EM (end of medium) 0111001 9 1011001 Y 1111001 y0011010 SUB (substitute) 0111010 : 1011010 Z 1111010 z0011010 SUB (substitute) 0111010 : 1011010 Z 1111010 z0011011 ESC (escape) 0111011 ; 1011011 [ 1111011 {0011011 ESC (escape) 0111011 ; 1011011 [ 1111011 {0011100 FS (file separator) 0111100 < 1011100 \ 1111100 |0011100 FS (file separator) 0111100 < 1011100 \ 1111100 |0011101 GS (group separator) 0111101 = 1011101 ] 1111101}0011101 GS (group separator) 0111101 = 1011101 ] 1111101}0011110 RS (record separator) 0111110 > 1011110 ^ 1111110 ~0011110 RS (record separator) 0111110 > 1011110 ^ 1111110 ~0011111 US (unit separator) 0111111 ? 1011111 _ 1111111 DEL0011111 US (unit separator) 0111111 ? 1011111 _ 1111111 DEL

100100101001111101101010000010010010100111110110101000001101101110000111001000100000110110111000011100100010000011000011110011010000011010001100001111001101000001101000110010111011001101100010000011001011101100110110001000001100001110111011001000100000110000111011101100100010000010010010100111110110101000001001001010011111011010100000110111011011111110100010000011011101101111111010001000001100111110111111010011101110110011111011111101001110111011001110100000111010011011111100111010000011101001101111010000011101001100001110101101000001110100110000111010111100101010000011010011110100110010101000001101001111010001000001100001110111011110010100000110000111011101111001010000011011011101111111001001000001101101110111111100101100101010000111001010100001

100100101001111101101010000010010010100111110110101000001101101110000111001000100000110110111000011100100010000011000011110011010000011010001100001111001101000001101000110010111011001101100010000011001011101100110110001000001100001110111011001000100000110000111011101100100010000010010010100111110110101000001001001010011111011010100000110111011011111110100010000011011101101111111010001000001100111110111111010011101110110011111011111101001110111011001110100000111010011011111100111010000011101001101111010000011101001100001110101101000001110100110000111010111100101010000011010011110100110010101000001101001111010001000001100001110111011110010100000110000111011101111001010000011011011101111111001001000001101101110111111100101100101010000111001010100001



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……to monochrome fax documents to monochrome fax documents that have been dissected into that have been dissected into microscopic slices of black and microscopic slices of black and

white strips…white strips…

……to monochrome fax documents to monochrome fax documents that have been dissected into that have been dissected into microscopic slices of black and microscopic slices of black and

white strips…white strips…length length whitewhite blackblack0 0 0011010100110101 000011011100001101111 1 000111000111 0100102 2 01110111 11113 3 10001000 10104 4 10111011 0110115 5 11001100 001100116 6 11101110 001000107 7 11111111 00011000118 8 1001110011 0001010001019 9 1010010100 00010000010010 10 0011100111 0000100000010011 11 0100001000 0000101000010112 12 001000001000 0000111000011113 13 000011000011 000001000000010014 14 110100110100 000001110000011115 15 110101110101 00001100000001100016 16 101010101010 0000010111000001011117 17 101011101011 0000011000000001100018 18 01001110100111 0000001000000000100019 19 00011000001100 0000100111000010011120 20 00010000001000 000011010000000110100021 21 00101110010111 000011011000000110110022 22 00000110000011 000001101110000011011123 23 00000110000011 000001010000000010100024 24 01010000101000 000000101110000001011125 25 01010110101011 000000110000000001100026 26 00100110010011 00001100101000001100101027 27 01001000100100 00001100101100001100101128 28 00110000011000 00001100110000001100110029 29 0000001000000010 00001100110100001100110130 30 0000001100000011 00000110100000000110100031 31 0001101000011010 000001101001000001101001

length length whitewhite blackblack32 32 0001101100011011 00000110101000000110101033 33 0001001000010010 00000110101100000110101134 34 0001001100010011 00001101001000001101001035 35 0001010000010100 00001101001100001101001136 36 0001010100010101 00001101010000001101010037 37 0001011000010110 00001101010100001101010138 38 0001011100010111 00001101011000001101011039 39 0010100000101000 00001101011100001101011140 40 0010100100101001 00000110110000000110110041 41 0010101000101010 00000110110100000110110142 42 0010101100101011 00001101101000001101101043 43 0010110000101100 00001101101100001101101144 44 0010110100101101 00000101010000000101010045 45 0000010000000100 00000101010100000101010146 46 0000010100000101 00000101011000000101011047 47 0000101000001010 00000101011100000101011148 48 0000101100001011 00000110010000000110010049 49 0101001001010010 00000110010100000110010150 50 0101001101010011 00000101001000000101001051 51 0101010001010100 00000101001100000101001152 52 0101010101010101 00000010010000000010010053 53 0010010000100100 00000011011100000011011154 54 0010010100100101 00000011100000000011100055 55 0101100001011000 00000010011100000010011156 56 0101100101011001 00000010100000000010100057 57 0101101001011010 00000101100000000101100058 58 0101101101011011 00000101100100000101100159 59 0100101001001010 00000010101100000010101160 60 0100101101001011 00000010110000000010110061 61 0011001000110010 00000101101000000101101062 62 0011001100110011 00000110011000000110011063 63 0011010000110100 000001100111000001100111

length length whitewhite blackblack64 64 1101111011 000000111000000111128 128 1001010010 000011001000000011001000192 192 010111010111 000011001001000011001001256 256 01101110110111 000001011011000001011011320 320 0011011000110110 000000110011000000110011384 384 0011011100110111 000000110100000000110100448 448 0110010001100100 000000110101000000110101512 512 0110010101100101 00000011011000000001101100576 576 01101000 01101000 00000011011010000001101101640 640 01100111 01100111 00000010010100000001001010704 704 011001100011001100 00000010010110000001001011768 768 011001101011001101 00000010011000000001001100832 832 011010010011010010 00000010011010000001001101896 896 011010011011010011 00000011100100000001110010960 960 011010100011010100 000000111001100000011100111024 1024 011010101011010101 000000111010000000011101001088 1088 011010110011010110 000000111010100000011101011152 1152 011010111 011010111 000000111011000000011101101216 1216 011011000011011000 000000111011100000011101111280 1280 011011001 011011001 000000101001000000010100101344 1344 011011010011011010 000000101001100000010100111408 1408 011011011 011011011 000000101010000000010101001472 1472 010011000 010011000 000000101010100000010101011536 1536 010011001 010011001 000000101101000000010110101600 1600 010011010 010011010 000000101101100000010110111664 1664 011000011000 000000110010000000011001001728 1728 010011011 010011011 000000110010100000011001011792 1792 00000001000 00000001000 00000001000000000010001856 1856 0000000110000000001100 00000001100000000011001920 1920 00000001101 00000001101 0000000110100000001101 1984 1984 000000010010000000010010 0000000100100000000100102048 2048 000000010011000000010011 0000000100110000000100112112 2112 000000010100000000010100 0000000101000000000101002176 2176 000000010101000000010101 0000000101010000000101012240 2240 000000010110000000010110 0000000101100000000101102304 2304 000000010111000000010111 0000000101110000000101112368 2368 000000011100000000011100 0000000111000000000111002432 2432 000000011101000000011101 0000000111010000000111012496 2496 000000011110000000011110 0000000111100000000111102560 2560 000000011111000000011111 000000011111000000011111



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……to color still images that are compressed to to color still images that are compressed to require a tiny fraction of their original memory require a tiny fraction of their original memory

storage space…storage space…

……to color still images that are compressed to to color still images that are compressed to require a tiny fraction of their original memory require a tiny fraction of their original memory

storage space…storage space…

554KB Original Image554KB Original Image554KB Original Image554KB Original Image 26KB Compressed Image26KB Compressed Image26KB Compressed Image26KB Compressed Image



Page 4Page Page 44

……to audio recordings that to audio recordings that are sampled thousands of are sampled thousands of

times per second, with each times per second, with each sample numerically sample numerically

approximated, …approximated, …

……to audio recordings that to audio recordings that are sampled thousands of are sampled thousands of

times per second, with each times per second, with each sample numerically sample numerically

approximated, …approximated, …

8 bits per sample8 bits per sample





Page 5Page Page 55

……and to video, in which temporal and spatial and to video, in which temporal and spatial redundancy limits the amount of data that redundancy limits the amount of data that

really needs to be transmitted.really needs to be transmitted.

……and to video, in which temporal and spatial and to video, in which temporal and spatial redundancy limits the amount of data that redundancy limits the amount of data that

really needs to be transmitted.really needs to be transmitted.

Frame kFrame k Frame k+1Frame k+1 Transmitted DifferenceTransmitted Difference

Temporal RedundancyConsecutive video frames are usually nearly identical, so

only their differences need to be calculated and transmitted

Temporal RedundancyConsecutive video frames are usually nearly identical, so

only their differences need to be calculated and transmitted

Spatial RedundancyWithin a single video frame, pixels tend to have nearly the same color as their neighbors, so, again, only

the color differences need to be sent

Spatial RedundancyWithin a single video frame, pixels tend to have nearly the same color as their neighbors, so, again, only

the color differences need to be sent



Page 6Page Page 66

One of the most common network standards is One of the most common network standards is Ethernet, which is used in most copper-based Ethernet, which is used in most copper-based

systems.systems.

One of the most common network standards is One of the most common network standards is Ethernet, which is used in most copper-based Ethernet, which is used in most copper-based

systems.systems.

EthernetEthernetEthernetEthernet

I haven’t heard anything I haven’t heard anything for a while, so I’m for a while, so I’m

sending!sending!

110100010101001010101010

Everything I’ve heard so far Everything I’ve heard so far is is exactlyexactly what I’ve been what I’ve been

sending!sending!

0011100100001010111100101001011011110100010101001010101010

I haven’t heard anything I haven’t heard anything for a while, so I’m for a while, so I’m

sending!sending!

111000111110100111100

100010101110100101010101101001011010101000010110101010101010101001010111010101000110111001010

That’sThat’s not what I not what I sent!sent!

COLLISION!!!COLLISION!!!

That’sThat’s not what I not what I sent!sent!

COLLISION!!!COLLISION!!!



Page 7Page Page 77

While copper cables transport electronic pulses While copper cables transport electronic pulses quickly, optical fiber makes it possible to quickly, optical fiber makes it possible to

communicate near the speed of light.communicate near the speed of light.

While copper cables transport electronic pulses While copper cables transport electronic pulses quickly, optical fiber makes it possible to quickly, optical fiber makes it possible to

communicate near the speed of light.communicate near the speed of light.

Fiber OpticsFiber OpticsFiber OpticsFiber Optics

In addition to its speed, optical fiber is less In addition to its speed, optical fiber is less susceptible to external interference and susceptible to external interference and requires less frequent signal refreshing.requires less frequent signal refreshing.

In addition to its speed, optical fiber is less In addition to its speed, optical fiber is less susceptible to external interference and susceptible to external interference and requires less frequent signal refreshing.requires less frequent signal refreshing.



Page 8Page Page 88

To take advantage of the capacity of To take advantage of the capacity of communication media to handle traffic, networks communication media to handle traffic, networks

are usually set up to share between multiple users are usually set up to share between multiple users simultaneously.simultaneously.

To take advantage of the capacity of To take advantage of the capacity of communication media to handle traffic, networks communication media to handle traffic, networks

are usually set up to share between multiple users are usually set up to share between multiple users simultaneously.simultaneously.

MultiplexingMultiplexingMultiplexingMultiplexing

Frequency-Division

Multiplexing Everyone gets to talk at the

same time, but only across their narrow

channels (e.g., traditional cable TV).

Time-Division Multiplexing

Everyone gets to talk using the

entire bandwidth, but

they have to take turns

talking (e.g., digital cable).

Code-Division MultiplexingCode-Division MultiplexingEveryone gets to talk simultaneously, Everyone gets to talk simultaneously, using the entire bandwidth! They do using the entire bandwidth! They do this by coding their transmissions in this by coding their transmissions in

a unique fashion, as if every pair a unique fashion, as if every pair were speaking a different language, were speaking a different language,

and each other language merely and each other language merely sounds like background noise (e.g., sounds like background noise (e.g.,

wireless networks).wireless networks).



Page 9Page Page 99

Delivering fast communications at affordable prices Delivering fast communications at affordable prices has caused some companies to think “outside the has caused some companies to think “outside the

box”.box”.

Delivering fast communications at affordable prices Delivering fast communications at affordable prices has caused some companies to think “outside the has caused some companies to think “outside the

box”.box”.

Updating Legacy SystemsUpdating Legacy SystemsUpdating Legacy SystemsUpdating Legacy Systems

In the late In the late 1970’s, the 1970’s, the

Southern Pacific Southern Pacific Railroad parlayed Railroad parlayed the right-of-way the right-of-way

that they had that they had already already

accumulated for accumulated for railroad tracks to railroad tracks to

build a build a nationwide nationwide optical fiber optical fiber

network, network, something AT&T something AT&T

and MCI were and MCI were unable to unable to

accomplish.accomplish.

In the late In the late 1970’s, the 1970’s, the

Southern Pacific Southern Pacific Railroad parlayed Railroad parlayed the right-of-way the right-of-way

that they had that they had already already

accumulated for accumulated for railroad tracks to railroad tracks to

build a build a nationwide nationwide optical fiber optical fiber

network, network, something AT&T something AT&T

and MCI were and MCI were unable to unable to

accomplish.accomplish.

Using new data Using new data compression compression

techniques, cable techniques, cable television systems television systems

find themselves with find themselves with unused network unused network

capacity, which they capacity, which they can make available for can make available for

Internet access via Internet access via cable modems.cable modems.

Using new data Using new data compression compression

techniques, cable techniques, cable television systems television systems

find themselves with find themselves with unused network unused network

capacity, which they capacity, which they can make available for can make available for

Internet access via Internet access via cable modems.cable modems.

Similarly, telephone Similarly, telephone companies are using companies are using

their excess their excess bandwidth to bandwidth to

provide Internet provide Internet access via digital access via digital subscriber lines.subscriber lines.

Similarly, telephone Similarly, telephone companies are using companies are using

their excess their excess bandwidth to bandwidth to

provide Internet provide Internet access via digital access via digital subscriber lines.subscriber lines.

http://www.sprint.com/



Page 10Page Page 1010

Originally devised as a DoD project for improving Originally devised as a DoD project for improving communication, the Internet is basically a massive communication, the Internet is basically a massive configuration of computers.configuration of computers.

Originally devised as a DoD project for improving Originally devised as a DoD project for improving communication, the Internet is basically a massive communication, the Internet is basically a massive configuration of computers.configuration of computers.

The InternetThe InternetThe InternetThe Internet

Internet BackboneInternet BackboneInternet BackboneInternet Backbone

Top Service ProvidersTop Service ProvidersTop Service ProvidersTop Service Providers

Universities, CorporationsUniversities, CorporationsUniversities, CorporationsUniversities, Corporations

Local ConnectionsLocal ConnectionsLocal ConnectionsLocal Connections

Routing DevicesRouting DevicesRouting DevicesRouting Devices

Traffic is routed through fast digital devices between “client” Traffic is routed through fast digital devices between “client” machines (e.g., PCs) and “server” machines (e.g., Web machines (e.g., PCs) and “server” machines (e.g., Web

servers).servers).

Traffic is routed through fast digital devices between “client” Traffic is routed through fast digital devices between “client” machines (e.g., PCs) and “server” machines (e.g., Web machines (e.g., PCs) and “server” machines (e.g., Web

servers).servers).




Search engines use “spider programs” to “crawl” Search engines use “spider programs” to “crawl” through the Web, building a list of words.through the Web, building a list of words.

Search engines use “spider programs” to “crawl” Search engines use “spider programs” to “crawl” through the Web, building a list of words.through the Web, building a list of words.

Internet Search EnginesInternet Search EnginesInternet Search EnginesInternet Search Engines

Some follow every Some follow every link on every home link on every home

page.page.

Some ignore links Some ignore links that lead to that lead to

graphics, sound, or graphics, sound, or animation files, or to animation files, or to

newsgroups.newsgroups.

Some concentrate Some concentrate primarily on the primarily on the

most popular Web most popular Web pages.pages.

Some follow every Some follow every link on every home link on every home

page.page.

Some ignore links Some ignore links that lead to that lead to

graphics, sound, or graphics, sound, or animation files, or to animation files, or to

newsgroups.newsgroups.

Some concentrate Some concentrate primarily on the primarily on the

most popular Web most popular Web pages.pages.




On-Line On-Line GamingGamingOn-Line On-Line GamingGaming

Sony Sony PlayStation2 and PlayStation2 and

Nintendo Nintendo GameCube make GameCube make

their own their own broadband broadband

network network adapters.adapters.

Sony Sony PlayStation2 and PlayStation2 and

Nintendo Nintendo GameCube make GameCube make

their own their own broadband broadband

network network adapters.adapters.

The rise of home network access The rise of home network access has fostered the development has fostered the development

and successful marketing of on-and successful marketing of on-line gaming systems.line gaming systems.

The rise of home network access The rise of home network access has fostered the development has fostered the development

and successful marketing of on-and successful marketing of on-line gaming systems.line gaming systems.

Microsoft Microsoft Xbox 360 has Xbox 360 has extended to extended to

wireless wireless network network

adapters…adapters…

Microsoft Microsoft Xbox 360 has Xbox 360 has extended to extended to

wireless wireless network network

adapters…adapters…

……as well as as well as wireless wireless

adapters for adapters for hand-held hand-held

controls and controls and headsets.headsets.

……as well as as well as wireless wireless

adapters for adapters for hand-held hand-held

controls and controls and headsets.headsets.

data communications

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