Basics Matter
Bits, Bytes & CodeMultiplexingCompression
Protocols & LANs
Figure 1.2Noise amplified on the analog line, eliminated on digital service.
Bits
• A bit = the smallest unit of information– On or off signals– Analog bits– Digital bits
Bytes
• 8 bits– A character
• Code - bytes in a common format• Examples of ASCII code
– 1110101 W– 1111110 ?– 1011000 Return
Figure 1.1One cycle of an analog wave, 1 hertz (Hz).
Broadband
• Multiple simultaneous streams
• Examples– Wireline– Wireless
• Why the growth?– Enterprises– Consumers
Compression
A way to make networks more efficientAbbreviating text
– Common charactersCompressing video
Not sending stationary objectsMatching compression algorithms at each
end
Where is Compression used?
Internet
What is its impact?
Figure 1.3Multiplexing.
Types of Multiplexing• Time division
Based on strict timingEveryone gets an equal turn
• Statistical divisionFirst come, first servedOr prioritization
Protocols
• A protocol is a set of rules for communicating between computers.
• Why are they needed?
Protocol Functions
• Who goes first?• Are you ready?• I got your message
• There are errors• This is a high priority
message• Who is sending?
How do Protocols Differ?
• HTML & XML• VoIP• Security protocols• Layer 3 vs. Layer 4
LANs
• Characteristics– Ownership– Limited geography– High speeds– Shared devices
• Devices on LANs• Changes in LANs
Figure 1.4LAN architecture.
Architecture: how devices fit together in a network.
Figure 1.5Rack-mounted and chassis-based switches.
The Work Environment
• How has the way your organization conducts business changed in the last five years?
• Which technologies have enabled these changes?
• What’s next?
Figure 1.6Home LAN.
Figure 1.7Edge and core routers.
Recap A Bit is ____
– Bits sent as analog signals have the following disadvantages:– Bits sent as digital signals the following advantages:
Bytes are: ASCII code is: Multiplexing makes better use of _____ by _____ Compression adds efficiencies to networks by ____ ______ changes the format of what is sent ______ does not change the format of what is transmitted
Recap Continued
Protocols are important because they: Layers simplify changes because they:
What do we mean by a layer 3 device versus a layer 4 device?
Characteristics of LANs are: Switches perform the following functions: Routers are needed to: Edge devices are more complex than core devices
because they: