Network Connectivity
and Mobility
BSAD 141
Dave Novak
Topics Covered

Lecture is structured based on the five
elements of creating a connected world from
the text book (with additional content)
Network Categories
 Network Providers
 Network Access Technologies
 Network Standards and Protocols
 Network Convergence

A Connected World

Five elements creating a connected world
Network Categories

1) LAN (local area network): a group of
computers sharing a common media –
usually in a small geographic area such as
a building

2) MAN (metropolitan area network):
network larger than a LAN – connects
computers over a larger geographic area

3) WAN (wide area network): largest
network that connects various LANs and
MANs throughout the world
Differences

LANs utilize high-speed, lower-cost shared
networking technologies such as Ethernet
and WiFi

MANs connect a group of LANs to various
network providers such cable TV providers,
local ISPs, telecom providers

WANs utilize very different networking
technologies than LANs – point-to-point,
higher-cost technologies that function across
large geographic areas
Differences
Data transfer
rate
LAN
WAN
High speed(≥ 1000 mbps)
Lower speed (≤ 155 mbps)
Network
technology
Tend to primarily use technologies that
are easy to set up and designed to
operate over short distances such as
Ethernet and WiFi
WANs tend to use more advanced
technologies designed to operate over large
distances such as MPLS, ATM, Frame Relay
& X.25
Components
Generally consist of layer 2 devices
like switches, bridges. To a lesser
extent layer1 devices like hubs &
repeaters
Layer 3 (+) devices such as routers, multilayer switches and technology specific devices
like ATM or Frame-relay Switches etc.
Fault
tolerance
LANs tend to have fewer problems
associated with them, as there are a
smaller number of systems to deal
with.
WANs tend to be less fault tolerant. as they
consist of a many different systems managed
by different organizations. There is a lower
amount of fault tolerance.
Typically owned, controlled, and
managed by a single organization
WANs are typically not owned by any one
organization but exist under collective or
distributed ownership and management over
long distances
Ownership
Costs
Low
High
LAN

LANs are categorized as “smaller” networks
that used a shared medium to connect
computers, printers, and other network
devices

Physical LANs are constrained
geographically to “small” areas

Buildings or floors of buildings

This is a function of the type of networking
technologies used
LAN

Computers and other devices such as
printers connect to the LAN via switches
and/or wireless access points

LANs connect to other larger networks (like
MANs and WANs) via routers
WAN

WANs are generally categorized as “large”
networks that connect other LANs and MANs
and operate across large geographical areas

Groups of buildings, Cities or municipalities,
regions of a country
WAN

WANs use different networking technologies
and protocols than LANs – specifically
technologies that operate over large areas

Messages that traverse a WAN are passed
from one router to another

Routing involves selecting the “best” path
through a network
LAN
WAN
Differences
Communication on a wired or wireless LAN
does not require the use of a router
 Communication off a wired or wireless LAN
(to another LAN), WAN, or the Internet
requires the use of a router
 For example, you can set up a LAN for local
communication, but traffic cannot come into
the LAN or leave the LAN unless some type
of router is used to provide a “doorway” to
another network

Terminology

The network medium is the physical
channel used to transmit data across a
network

Copper wires, fiber optics, radio waves…
Networking Technology

There are MANY different networking
technologies – both for LANs and WANs

Network technology - a standards-based
combination of hardware, software, and
protocols

Examples of networking technologies:
• Ethernet
• WiFi
• Asynchronous Transfer Mode (ATM)
Networking Technology
Ethernet is the most popular and widely
used wired LAN networking technology
 There are many different Ethernet
standards that use different media
(different types of cabling), different
topologies and support different
bandwidths


10/100/1000
Networking Technology

Ethernet frame (IEEE 802.3) v2 length >= 1536 B
Preamble
SFD
8 bytes

1
Dest.
MAC
Source
MAC
Length
6
6
2
DATA
FCS
46 – 1500 bytes
4
Token Ring frame (IEEE 802.5) length > 4500 B
Start
Del.
1
Access Frame
Control Control
1
1
Dest.
MAC
6
Source
MAC
6
DATA
4500 >= 0
FCS
End
Del.
Frame
Status
4
1
1
Networking Technology

WiFi is a commonly used wireless
technology used on LANs that provides
relatively high-speed, but short range
connectivity

Benefits
• Inexpensive, quick & easy

Drawbacks
• Security, distance limitations, speed
Networking Technology

What is the difference between WiFi and the
general term “wireless”?
Source: http://retailtechnologytrends.com/2010/11/05/2010-45-whats-the-difference-between-wifi-and-wireless/
Networking Technology

What is Bluetooth?
Networking Hardware

Network Interface Card

Switch

Router
Network Providers

National service providers (NSPs) Private companies that own and maintain the
backbone networks that support the Internet

Network access points (NAPs) - Traffic
exchange / aggregation points in the routing
hierarchy of the Internet that connect ISPs

Internet service providers (ISPs) –
Regional and local “gateways” to the Internet
that connect to NSPs and can connect
directly to each other
Network Providers
Network Terminology

Bandwidth

Throughput
Network Terminology

When your ISP uses the term “broadband”
what do they mean?
Network Access
Technologies

Corporate connectivity options
1) Point-to-point leased lines
 2) Public Telephone Network (PSTN)
 3) Virtual Private Network (VPN)


Home connectivity options
1) Dialup modem
 2) DSL modem
 3) Cable modem
 4) WiFi

Point-to-point
Communication

Communication channel rented from a
service provider
Using the existing telecommunications
infrastructure system
 Typically considered a private service


Different technologies and bandwidth options
depending on provider

Optical fiber versus copper wire
Point-to-point
Communication

Customers pay a monthly fee for dedicated
use of a communication channel

Fee depends on bandwidth, the networking
technology being used, and on Quality-ofService (QoS) guarantees
PSTN

The wired telecommunications network that
supports landline telephone usage

This is a circuit-switched network while data
networks are packet-switched – the
relevance of this statement with respect to
our class is that this network is not designed
for data usage, but for voice-based phone
usage
PSTN
PSTNs provide much of the intra and intercontinental (long-distance) communication
infrastructure that we consider to be “part of”
the internet
 Internet Service Providers (ISPs) pay longdistance telecom providers (the owners of
the PSTN like MCI, Sprint, AT&T, etc.) for
access to their networks – in turn, customers
of ISPs pay the ISP

PSTN
Users of the public internet (most customers)
gain access to the PSTN through their ISP
 With respect to home-based users, the
PSTN is generally considered to be a
shared communication channel

Public versus Private??

Public – users pay fees to use a shared
network
Could be “pay-as-you-go” approach
 Parts of the physical infrastructure network
are available to the general public


Private – users pay fees to obtain a
dedicated portion of the network
Usually a “flat fee” approach
 Parts of the physical infrastructure network
are “set-aside” or dedicated just for the renter

Shared versus Dedicated??

Shared – media / channel capacity is used
jointly by multiple users or applications as
needed


Envision a toll road
Dedicated – media / channel capacity is
used exclusively by a single user or
application

Envision a toll road where users paid to
reserve their own lane and no one else can
use that lane
Point-to-Point and PSTN

In many cases we are talking about
“classification” or stratification of the same
physical infrastructure network…

For example, AT&T can provide users with
both options:
Point-to-point services
 Public PSTN services

Virtual Private Network
(VPN)
Relies on PSTN “public / shared” network
service but provides users with secure /
private access to their organization’s network
 Idea is to leverage the low cost of a public /
shared network with the security of a private
network


Goal – same “security” as point-to-point
leased lines at a fraction of the cost
Virtual Private Network
(VPN)
Accomplished by installing VPN client-side
software and having client computers
connect directly to the VPN server on the
organization’s “home” network
 Uses special “tunneling protocols” to encrypt
data at the sending end and decrypt the data
at the receiving end essentially masking or
hiding the private information


PPTP, L2TP
Virtual Private Network
(VPN)

VPN requires special software for
each connected site

Allows only secure communication
between remote host and VPN server
– protects from unauthorized access
Virtual Private Network
(VPN)
Users connect through to PSTN via
dialup or another access method
 User establishes connection with her
organization’s Network Access Server
using VPN client-side software and
provides A/A credentials
 Uses tunneling protocols (such as
PPTP, L2TP) to encapsulate data
before sent across PSTN

Virtual Private Network
(VPN)

Secure connection established over
the Internet via PPTP
Connection established between
remote host and NAS /
VPN server
Data are encapsulated
Virtual Private Network
(VPN)

Great!! – low cost + secure – why wouldn’t
you do this?
Design and implementation is extremely
complex
 Reliability can be an issue and depends on
the network provider

• Higher QoS  higher $$
As you scale up, compatibility issues may
arise
 Security issues if wireless is employed

Dialup (modem) with PSTN

Digital signal from PC converted to analog
signal for transmission over phone lines by
modem

Used for dial-up Internet connections and
some WAN technologies
• http://www.dialupsound.com/

Why are dialup modems so slow?
Digital Subscriber Line
(DSL)

Network connection technology that uses
standard telephone lines, but achieves
greater speeds than dialup
Supports multiple voice, data, and video
channels over a single line
 How is this possible?

Digital Subscriber Line
(DSL)
Services running at different down/up stream
speeds are referred to as Asymmetric
 Services running at same down/up stream
speeds are referred to as Symmetric


Why might there be a difference here?
Cable TV Internet (CATV)
Cable company solution to high-speed
Internet access
 Here, we discuss a CATV modem, which
uses same physical cable as TV
 See for interesting discussion on differences
between modem, Netflix, Google TV
http://www.pcmag.com/encyclopedia/term/39
164/cable-internet

Cable TV Networks (CATV)




Higher bandwidth than dialup but not
necessarily higher than DSL – depends on
service provider and how much you are willing
to pay
Asymmetric service
Shared technology - you are essentially sharing
the network bandwidth with your neighbors
DSL and dialup are dedicated connections
Network Standards and
Protocols

Protocol - a formal set of steps and rules
that specifies the format of data as well as
the rules to be followed during transmission
(TCP, IP, HTTP, DHCP, …)

Standard – agreed upon sets of guidelines
and definitions to allow different products
and services from different manufacturers to
work together (ANSI SQL, IEEE 802.3,…)
Network Protocols

Computers use MANY protocols even during
simple data exchanges

Enable communication between
Different computers
 Different hardware within the computer
 Different software within the computer
 Hardware and software within the computer


Protocols specify how communication
occurs and the form it takes
Network Protocols

Transmission control protocol/Internet
protocol (TCP/IP) - Provides the technical
foundation for the internet as well as for large
numbers of private networks
Referred to as the “Internet Protocol Stack”
 There are many more protocols that comprise
the TCP/IP stack – these are the foundational
protocols
 All protocols have different “jobs”

Network Protocols

Internet Protocol (IP)

Provides a generic address understood by all
devices on the Internet
• Independent of specific networking technologies

Routes all IP datagrams independently
• No guarantee that packets will travel on same
route to destination

Allows for fragmentation and reassembly of
datagrams
• Can subdivide datagrams to fit in any frame
payload
Network Protocols

Transmission Control Protocol (TCP)

Provides reliable service
• Address out of order delivery
• Address packet loss
• Adjust routing based on network conditions
(congestion control)
• Adjust how many packets are sent in a given time
period (flow control)
• Establish an explicit “connection” between sender
and receiver
• Address corrupt data
The Internet

A global WAN connecting millions of
individual computers and networks
Allows different networks (LANs, MANs,
WANs) all using different networking
technologies to communicate as if they were
operating on a single network
 Uses a client-server architecture

• Client requests some type of service from a
remote PC providing that service (a server)
The Internet
No one “owns” the Internet (per se)
 Different groups, organizations, or individuals
may “own” or manage different physical
infrastructure networks that are connected
to, or comprise, the internet

The Internet

World Wide Web (WWW)
WWW is NOT the same thing as the Internet
 Connect to the Web via a graphical browser
such as IE or Netscape
 Web browsers “open” a Uniform Resource
Locator (URL)

• URL provides information about the location of
things on the Web
• For example http://www.bsad.uvm.edu

The Internet is a global WAN that supports all
types of different technologies
Network Convergence

The movement toward the combination of
different services such as voice, video, and
data on a single network infrastructure
One physical network handles multiple
services instead of voice over telephone
networks and data over data networks
 Why are we even bringing this up?

Network Convergence
Problem: different physical networks utilize
different networking technologies
 The individual technologies are not designed
to communicate with one another
 Different technologies are “better” for certain
types of services
 Use of TCP/IP allows heterogeneous
networks to communicate

Network Convergence
Network infrastructure is not “free” and is
mostly owned by private organizations
 Networking infrastructure is expensive and
organizations do not “casually” build new
networks explicitly for the “good of humanity”
 Make a profit or at least recover costs


But this means that some people can’t afford
access…
Summary

Following the 5 category format from the
book
Network Categories: LAN, MAN, WAN
 Network Technologies: Ethernet and WiFi
 Network Providers
 Network Standards and Protocols
 Network Convergence
