Download Slides Topic 3

Topic 3
Networks and the Internet
Three Important Networking Technologies
Networks, Internet, WWW
A Modem
0011101
M
M
0011101
Networks, Internet, WWW
Data communications
Sending messages/information between two or
more computers.
Client
Client
Server
Printer
Client
File system
Client
Upstream
Downstream
Data communications media
Example Connections & Service
Implementation
Example
Speed
Multiplier
Dial Up Modem
56 kbps
1
Wireless S
500 kbps
10X
S
Wireless 3G MT
1,500 kbps
30X
MT
DSL
1+ Mbps
20X
TP
Cable Modem
2+ Mbps
40X
C
Ethernet LAN
10 - 100 Mbps
200X – 2,000X
TP, C, F
T1, T2, T3
OC-192
Media
TP, C, F
10,000 Mpbs
200,000X
F
Notes:
TP=Twisted Pair, C=Coaxial Cable, F=Fiber, S=Satellite, MT=Microwave Towers/cellular
T1, T2, T3 are dedicated lines from Org to ISP or ISP to Internet
OC Internet backbone lines
http://mindprod.com/jgloss/transmissionspeed.html
http://indianblogger.com/understanding-the-generations-1g-2g-3g-and-4g/
Data Communication
• Network: two or more computers or devices linked
by communication lines.
– Each computer/device is a node
– Transmitter and receiver are nodes
• The network is the medium
• Communication rules are defined by a protocol
Data Communication
• Communication protocol
– An agreed-upon format or procedure for
transmitting data.
– Implemented in hardware and/or software
• Key issues
– Deliver message efficiently
– Detect errors
– Correct errors
Networks, Internet, WWW – 5 of 22
Messages and Packets
Trailer
Packet A1
Message A
Body
Packet A2
Header
Packet A3
A Packet
Version
(4 bits)
Diff-Serv
(8 bits)
Flow Label (20 bits)
Marks a packet as part of a specific flow
Next Header
(8 bits)
Payload Length (16 bits)
Name of next
header
Source IP Address (128 bits)
Destination IP Address (128 bits)
Next Header or Payload (Data Field)
Hop Limit
(8 bits)
Routers
Router 1
Router 4
Router 4
Internet
Router 2
Routers
Router 1
Router 6
Router 8
Router 3
Router 4
Router 4
Router 2
Router 5
Router 5
Router 5
Router 7
Router 9
Sending Messages Across a Network
Message A
Packet A1
Packet A2
Packet A3
Packet A3
Packet
Packet
Packet A1
Packet
Open
Packet
Packet A2
Packet
Packet
Packet
Open
Open
Packet
Packet
Packet
Packet
Packet
Packet A1
Packet A2
Message A
Packet A3
U.S. Internet Backbone
Networks, Internet, WWW – 1 of 20
LANs and WANs
• LAN (local area network)
– A network that connects systems within a limited
physical area (department, dorm).
• WAN (wide area network)
– A network that connects systems throughout a
large geographic area (entire business,
university/branches).
A LAN
Client
Client
Server
Printer
Client
File system
Client
A WAN
Internetworking
• Process of
linking two
or more
networks.
Workstation
Workstation
Workstation
Workstation
Workstation
Workstation
Server
Bridge
Server
A bridge links
similar networks
Workstation
A gateway links
dissimilar networks
Workstation
Server
Gateway
Workstation
Workstation
Router and a Switch
Internet Addressing
sbaserver1.sba.muohio.edu
Top-level domain
Miami University domain
SBA sub-domain
Server within SBA sub-domain
Internet Addressing
sbaserver1.sba.muohio.edu
134.53.40.2
• Physical transmission requires IP address
• Domain name system converts domain name to equivalent
IP address
Internet Addressing
http://www.visualware.com/
http://www.whatismyip.com/
Internet Addressing
TCP/IP
Summary: TCP and IP were developed by a Department of Defense (DOD) research project to connect a number different
networks designed by different vendors into a network of networks (the "Internet"). It was initially successful because it
delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large number of
client and server systems. Several computers in a small department can use TCP/IP (along with other protocols) on a single
LAN. The IP component provides routing from the department to the enterprise network, then to regional networks, and
finally to the global Internet. On the battlefield a communications network will sustain damage, so the DOD designed TCP/IP
to be robust and automatically recover from any node or phone line failure. This design allows the construction of very large
networks with less central management. However, because of the automatic recovery, network problems can go undiagnosed
and uncorrected for long periods of time.
As with all other communications protocol, TCP/IP is composed of layers:
•IP - is responsible for moving packet of data from node to node. IP forwards each packet based on a four byte
destination address (the IP number). The Internet authorities assign ranges of numbers to different organizations. The
organizations assign groups of their numbers to departments. IP operates on gateway machines that move data from
department to organization to region and then around the world.
•TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the
intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is
correctly and completely received.
•Sockets - is a name given to the package of subroutines that provide access to TCP/IP on most systems.
TCP/IP
TCP is a connection-oriented transport protocol that sends data as an unstructured stream of
bytes. By using sequence numbers and acknowledgment messages, TCP can provide a sending
node with delivery information about packets transmitted to a destination node. Where data has
been lost in transit from source to destination, TCP can retransmit the data until either a timeout
condition is reached or until successful delivery has been achieved. TCP can also recognize
duplicate messages and will discard them appropriately. If the sending computer is transmitting
too fast for the receiving computer, TCP can employ flow control mechanisms to slow data
transfer. TCP can also communicate delivery information to the upper-layer protocols and
applications it supports.