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: