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Computer Science E-1Understanding Computers and the Internet
Lecture 4: The Internet, continuedFebruary 28, 2011
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Networking IP Addresses
Canonical Form (IPv4): #.#.#.#
# is 0-255
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Networking DNS
Client
IP ofcnn.com
DNS Server
64.236.16.20
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The Internet Domains
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Domain
harvard.edu
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Domains TLDs from 1995
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.com.edu.gov.mil.net.org
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Domains TLDs Now
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Generic TLDs .aero .asia .biz .cat .com .coop .edu .gov .info .int .jobs .mil .mobi .museum .name .net .org .pro .tel .travel
Country Code TLDs
.ac .ad .ae .af .ag .ai .al .am .an .ao .aq .ar .as .at .au
.aw .ax .az .ba .bb .bd .be .bf .bg .bh .bi .bj .bm .bn
.bo .br .bs .bt .bv .bw .by .bz .ca .cc .cd .cf .cg .ch
.ci .ck .cl .cm .cn .co .cr .cu .cv .cx .cy .cz .de .dj .dk
.dm .do .dz .ec .ee .eg .er .es .et .eu .fi .fj .fk .fm .fo
.fr .ga .gb .gd .ge .gf .gg .gh .gi .gl .gm .gn .gp .gq .gr
.gs .gt .gu .gw .gy .hk .hm .hn .hr .ht .hu .id .ie .il .im
.in .io .iq .ir .is .it .je .jm .jo .jp .ke .kg .kh .ki .km .kn
.kp .kr .kw .ky .kz .la .lb .lc .li .lk .lr .ls .lt .lu .lv .ly .ma
.mc .md .me .mg .mh .mk .ml .mm .mn .mo .mp .mq
.mr .ms .mt .mu .mv .mw .mx .my .mz .na .nc .ne .nf
.ng .ni .nl .no .np .nr .nu .nz .om .pa .pe .pf .pg .ph
.pk .pl .pm .pn .pr .ps .pt .pw .py .qa .re .ro .rs .ru .rw
.sa .sb .sc .sd .se .sg .sh .si .sj .sk .sl .sm .sn .so .sr
.st .su .sv .sy .sz .tc .td .tf .tg .th .tj .tk .tl .tm .tn .to
.tp .tr .tt .tv .tw .tz .ua .ug .uk .um .us .uy .uz .va .vc
.ve .vg .vi .vn .vu .wf .ws .ye .yt .yu .za .zm .zw
Information from http://www.iana.org/domain-names.htm
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Domains Sub-Domains
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Domain Sub-Domains
harvard.edudce., fas., eecs., post., law., etc
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Networking Services, Servers, Clients
Server
Network
Client
Images from apple.com (© Apple, Inc) and dell.com (© Dell)
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Networking Peer-to-Peer
Peer
Network
Peer
Images from dell.com (© Dell)
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The Internet Protocols
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FTP File Transfer ProtocolHTTP HyperText Transfer ProtocolIMAP Internet Message Access ProtocolNTP Network Time ProtocolPOP3 Post Office Protocol Version 3RTSP Real-time Transport Streaming ProtocolSSH Secure ShellSMTP Simple Mail Transfer Protocol
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Networking TCP/IP Model
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Image adapted from http://en.wikipedia.org/wiki/Internet_protocol_suite
5 Application
4 Transport
3 Internet
2 Link
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Networking IP Packets
Internet Header Format
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| IHL |Type of Service| Total Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification |Flags| Fragment Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time to Live | Protocol | Header Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Example Internet Datagram Header
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Networking TCP Packets
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TCP Header Format
0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Port | Destination Port | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Acknowledgment Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data | |U|A|P|R|S|F| | | Offset| Reserved |R|C|S|S|Y|I| Window | | | |G|K|H|T|N|N| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Checksum | Urgent Pointer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
TCP Header Format
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Networking DHCP
Client
I need an IP!
DHCP Server
192.168.0.2
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Network Devices Hub and Switch Review
Hub
A B
DC
Switch
A B
DC
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Network Devices Hub and Switch Collisions
Hub
A B
DC
Switch
A B
DC
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Network Devices Wireless access point
A B
DC
AP
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Network Devices Router
A B
DC
RouterInternet
(other routers)
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Network Devices Adding IP addressing
192.168.0.2 192.168.0.3
192.168.0.5192.168.0.4
RouterInternet
(other routers)
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Internet
Networking NAT
Client
Server
Router
24.28.4.43 64.236.16.20
192.168.0.1192.168.0.2
Network
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Internet
Networking VPN
Client
192.168.0.2 Network
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192.168.0.3 192.168.0.4
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Networking Firewall
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Network Devices Home Routers
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The Internet ISPs
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Computer Science E-1Understanding Computers and the Internet
Lecture 4: The Internet, continuedFebruary 28, 2011
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