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 CategoriesNetwork ProvidersNetwork Access TechnologiesNetwork Standards and ProtocolsNetwork 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

DifferencesLAN WAN

Data transfer rate 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, multi-layer 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.

Ownership

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

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 buildingsThis 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 areasGroups 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 networkCopper 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 protocolsExamples 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 bandwidths10/100/1000

Networking Technology

Ethernet frame (IEEE 802.3) v2 length >= 1536 B

Token Ring frame (IEEE 802.5) length > 4500 B

Dest.MAC

SourceMAC

Length DATA FCSPreamble SFD

8 bytes 1 6 6 2 46 – 1500 bytes 4

StartDel.

AccessControl

FrameControl

Dest.MAC

SourceMAC

DATA FCS EndDel.

FrameStatus

1 1 1 6 6 4500 >= 0 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 & easyDrawbacks

• 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 lines2) Public Telephone Network (PSTN)3) Virtual Private Network (VPN)

Home connectivity options1) Dialup modem2) DSL modem3) Cable modem4) WiFi

Point-to-point Communication Communication channel rented from a

service providerUsing the existing telecommunications

infrastructure systemTypically considered a private service

Different technologies and bandwidth options depending on providerOptical fiber versus copper wire

Point-to-point Communication Customers pay a monthly fee for dedicated

use of a communication channelFee depends on bandwidth, the networking

technology being used, and on Quality-of-Service (QoS) guarantees

PSTN The wired telecommunications network that

supports landline telephone usageThis 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 inter-

continental (long-distance) communication infrastructure that we consider to be “part of” the internet

Internet Service Providers (ISPs) pay long-distance 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” approachParts 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” approachParts 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 neededEnvision a toll road

Dedicated – media / channel capacity is used exclusively by a single user or applicationEnvision 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 servicesPublic 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 networkGoal – 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 informationPPTP, L2TP

Virtual Private Network(VPN)

VPN requires special software for each connected siteAllows 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 betweenremote 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

complexReliability 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 modemUsed 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 dialupSupports multiple voice, data, and video

channels over a single lineHow 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 SymmetricWhy 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/39164/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 computersDifferent hardware within the computerDifferent software within the computerHardware 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 networksReferred 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 destinationAllows 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 networksAllows 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 InternetConnect to the Web via a graphical browser

such as IE or NetscapeWeb 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 infrastructureOne 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 bookNetwork Categories: LAN, MAN, WANNetwork Technologies: Ethernet and WiFiNetwork ProvidersNetwork Standards and ProtocolsNetwork Convergence