Unit 4 - Section 1

equableunalaskaSecurity

Dec 9, 2013 (3 years and 8 months ago)

83 views

1/28/2010

1/28/2010

Network Plus

Unit 4
-

Section 1


Wide Area Network Technologies

Connecting to the Internet

Internet connections may
be Wired or Wireless. In
this section we will look at
wired connections using
either the Telephone or
Cable networks.

PSTN


PSTN (Public Switched Telephone Network)


Network of lines, carrier equipment providing telephone service


POTS (plain old telephone service)


Encompasses entire telephone system


Originally: analog traffic


Today: digital data, computer controlled switching


Dial
-
up connection


Modem connects computer to distant network


Works from almost anywhere


DSL


Provides high speed, continuous Internet connect where
available


Multiple types of DSL connections


13

4

PSTN Topologies

Figure 7
-
2 A bus
topology WAN

Figure 7
-
3 A ring
topology WAN

Network+ Guide to Networks, 5
th

Edition

10

Mesh and Tiered

Figure 7
-
5 Full
-
mesh and partial
-
mesh WANs

DSL


DSL (digital subscriber line)


Operates over PSTN at physical layer


Directly competes with other PSTN services such as
ISDN and T1


Shares voice and data over same line


Uses high frequency range, inaudible telephone line
frequencies


Voices uses only 300


3000 Hz


Uses advanced data modulation techniques


Amplitude or phase modulation

37

Network+ Guide to Networks, 5
th

Edition

38

Types of DSL


xDSL refers to all DSL varieties


ADSL, G.Lite, HDSL, SDSL, VDSL, SHDSL


Two DSL categories


Asymmetrical and symmetrical


Downstream


Data travels from carrier’s switching facility to
customer


Upstream


Data travels from customer to carrier’s switching
facility

Network+ Guide to Networks, 5
th

Edition

40

Types of DSL (cont’d.)


How DSL types vary


Data modulation techniques


Capacity


Distance limitations


PSTN use

Table 7
-
2

Comparison of DSL types

Network+ Guide to Networks, 5
th

Edition

43

DSL Connectivity (cont’d.)

Figure 7
-
17 A DSL connection

Broadband Cable


Cable companies connectivity option


Based on TV signals coaxial cable wiring


Theoretically transmission


150 Mbps downstream, 10 Mbps upstream


Real transmission


10 Mbps downstream, 2 Mbps upstream


Transmission limited ( throttled)


Shared physical connections


Best use


Web surfing


Network data download

Network+ Guide to Networks, 5
th

Edition

45

Network+ Guide to Networks, 5
th

Edition

46

Broadband Cable (cont’d.)


Requires cable modem


Modulates, demodulates transmission, reception
signals via cable wiring


Operates at Physical and Data Link layer


May connect to connectivity device

Figure 7
-
18 A cable modem

WAN Technologies


WAN technologies are used to provide high
bandwidth connection between major data centers.


In this section we will look at some older as well as
current WAN technologies.

X.25 and Frame Relay


X.25 ITU standard


Analog, packet
-
switching technology from 1970s


Mainframe to remote computers: 64 Kbps throughput


Update: 1992


2.048 Mbps throughput


Client, servers over WANs


Operates at Physical, Data Link, and Network layers.


Verifies transmission at every node


Excellent flow control, ensures data reliability


Slow for time
-
sensitive applications

Network+ Guide to Networks, 5
th

Edition

15

Network+ Guide to Networks, 5
th

Edition

16

Frame Relay


Frame relay


Updated X.25: digital, packet
-
switching


Protocols operate at Data Link layer


Supports multiple Network, Transport layer protocols


No data delivery guarantee


Customer chooses data speed


Use Virtual Circuits


PVC


Permanent Virtual Circuit


SVC


Switched Virtual Circuit

Network+ Guide to Networks, 5
th

Edition

20

Frame Relay

Figure 7
-
9 A WAN using frame relay

Network+ Guide to Networks, 5
th

Edition

21

ISDN


Digital data transmitted over PSTN


Gained popularity: 1990s


Connecting WAN locations


Exchanges data, voice signals


Protocols at Physical, Data Link, Transport layers


Relies on PSTN for transmission medium


Dial
-
up or dedicated connections


Dial
-
up relies exclusively on digital transmission

Network+ Guide to Networks, 5
th

Edition

22

ISDN Channel Types


Two channel types


B channel: “bearer”


Circuit switching for voice, video, audio: 64 Kbps


D channel: “data”


Packet
-
switching for call information: 16 or 64 Kbps


BRI (Basic Rate Interface) connection


PRI (Primary Rate Interface) connection


Network+ Guide to Networks, 5
th

Edition

23


BRI: two B channels, one D channel (2B+D)


B channels treated as separate connections


Carry voice and data


Bonding


Two 64
-
Kbps B channels combined


Achieve 128 Kbps

Figure 7
-
10 A BRI link

Network+ Guide to Networks, 5
th

Edition

24


PRI: 23 B channels, one 64
-
Kbps D channel
(23B+D)


Separate B channels independently carry voice, data


Maximum throughput: 1.544 Mbps


PRI and BRI may interconnect

Figure 7
-
11 A PRI link

ATM (Asynchronous Transfer Mode)


Functions in Data Link layer


Asynchronous communications method


Nodes do not conform to predetermined schemes


Specifying data transmissions timing


Each character transmitted


Start and stop bits


Specifies Data Link layer framing techniques


Fixed packet size sets ATM apart from Ethernet


Packet (cell)


48 data bytes plus 5
-
byte header = 53 byts

Network+ Guide to Networks, 5
th

Edition

49

Network+ Guide to Networks, 5
th

Edition

50

ATM (cont’d.)


Smaller packet size requires more overhead


Decrease potential throughput


Cell efficiency compensates for loss


ATM relies on virtual circuits


ATM considered packet
-
switching technology


Virtual circuits provide circuit switching advantage


Circuit path setup by switches in advance


Reliable connection


Allows specific QoS (quality of service) guarantee


Important for time
-
sensitive applications


Often used on SONET rings

Network+ Guide to Networks, 5
th

Edition

25

T
-
Carriers


T1s, fractional T1s, T3s


Physical layer operation


Single channel divided into multiple channels


Using TDM (time division multiplexing) over two wire
pairs


Medium


Telephone wire, fiber
-
optic cable, wireless links

Network+ Guide to Networks, 5
th

Edition

26

Types of T
-
Carriers


Many available


Most common: T1 and T3

Table 7
-
1 Carrier specifications

Network+ Guide to Networks, 5
th

Edition

31


Smart Jack


Terminate T
-
carrier wire pairs


Customer’s demarc (demarcation point)


Inside or outside building


Connection monitoring point

Figure 7
-
12 A T1 smart jack

Network+ Guide to Networks, 5
th

Edition

32

T
-
Carrier Connectivity (cont’d.)


CSU/DSU (Channel Service Unit/Data Service Unit)


Two separate devices


Combined into single stand
-
alone device


Interface card


T1 line connection point


At customer’s site


CSU


Provides digital signal termination


Ensures connection integrity

Network+ Guide to Networks, 5
th

Edition

34

T
-
Carrier Connectivity (cont’d.)


Incoming T
-
carrier line


Multiplexer separates combined channels


Outgoing T
-
carrier line


Multiplexer combines multiple LAN signals

Figure 7
-
14 A point
-
to
-
point T
-
carrier connection

Network+ Guide to Networks, 5
th

Edition

52

SONET (Synchronous Optical Network)


Four key strengths


WAN technology integration


Fast data transfer rates


Simple link additions, removals


High degree of fault tolerance


Synchronous


Data transmitted, received by nodes conforms to
timing scheme


Advantage


Interoperability

Network+ Guide to Networks, 5
th

Edition

54

SONET (cont’d.)


Fault tolerance


Double
-
ring topology over fiber
-
optic cable


SONET Ring


Begins, ends at telecommunications carrier’s facility


Connects organization’s multiple WAN sites in ring
fashion


Connect with multiple carrier facilities


Additional fault tolerance


Terminates at multiplexer


Easy SONET ring connection additions, removals

Network+ Guide to Networks, 5
th

Edition

55

SONET (cont’d.)

Figure 7
-
21 SONET connectivity

Network+ Guide to Networks, 5
th

Edition

53

SONET (cont’d.)

Figure 7
-
20 A SONET ring

Network+ Guide to Networks, 5
th

Edition

56

SONET (cont’d.)


Data rate


Indicated by OC (Optical Carrier) level

Table 7
-
3 SONET OC levels

Network+ Guide to Networks, 5
th

Edition

58

WAN Technologies Compared

Table 7
-
4 A comparison of WAN technology throughputs

Remote Access


Remote access is used to allow users to connect to
a network or single computer from a remote
location.

Network+ Guide to Networks, 5
th

Edition

63

Remote Access Servers

Figure 7
-
22 Clients connecting with a remote access server

Remote Access Protocols


SLIP and PPP


Workstations connect using dial
-
up connection


Encapsulate higher
-
layer networking protocols, in
lower
-
layer data frames


SLIP carries
IP packets only


Harder to set up


Supports only asynchronous data


PPP carries many different Network layer packets


Automatic set up


Performs error correction, data compression, supports
encryption


Supports asynchronous and synchronous transmission

Network+ Guide to Networks, 5th Edition

64

Network+ Guide to Networks, 5
th

Edition

65

Remote Access Protocols (cont’d.)


PPPoE (PPP over Ethernet) standard


Connects home computers to ISP


Via DSL, broadband cable

Figure 7
-
23 Protocols used in a remote access Internet connection

Network+ Guide to Networks, 5
th

Edition

68

Remote Desktop and Remote
Assistance


Remote desktop


Windows client and server operating systems


Relies on RDP (Remote Desktop Protocol)


Application layer protocol


Uses TCP/IP to transmit graphics, text quickly


Carries session, licensing, encryption information


Exists for other operating systems


Not included in Windows home editions


Uses Port 3389 by default

Network+ Guide to Networks, 5
th

Edition

69

Figure 7
-
24 Remote tab in the Windows XP System Properties window

Remote Desktop Infrastructure

RDI


Uses virtual machines running on a server


One server can host many desktop OS environments


Uses Thin client for users


Remote virtual computing software requires little
bandwidth


Useful in BYOD environments


Network+ Guide to Networks, 5
th

Edition

73

VPNs (Virtual Private Networks)


Uses tunnel to Isolate traffic from other public line traffic


Software


Inexpensive


Sometimes included with other widely used software


Tailored to customer’s distance, bandwidth needs


Two important design considerations


Interoperability and security

Network+ Guide to Networks, 5
th

Edition

74


Tunneling


Ensures VPN carries all data types privately


Tunnel


Virtual connection between two VPN nodes

Figure 7
-
26 An example of a VPN

Network+ Guide to Networks, 5
th

Edition

75

VPNs (cont’d.)


Types of tunneling


PPTP (Point
-
to
-
Point Tunneling Protocol)


Microsoft


Authentication and minimal encryption


L2TP (Layer 2 Tunneling Protocol)


Cisco


Uses IPSec encryption at Network Layer to provide
strong security


SSL VPN


Uses SSL encryption at Presentation level


Establishes connection at Browser level

SSL VPN


An SSL VPN (Secure Sockets Layer virtual private
network) is a form of
VPN

that can be used with a
standard Web browser.


In contrast to the traditional Internet Protocol
Security (IPsec) VPN, an SSL VPN does not require
the installation of specialized client software on the
end user's computer.


Used to give remote users with access to Web
applications, client/server applications and internal
network connections.


Open VPNs


There are three major families of VPN implementations in wide usage
today: SSL, IPSec, and PPTP. OpenVPN is an SSL VPN and as such is not
compatible with IPSec, L2TP, or PPTP.


The IPSec protocol is designed to be implemented as a modification to the IP
stack in kernel space, and therefore each operating system requires its own
independent implementation of IPSec.


By contrast, OpenVPN's user
-
space implementation allows portability across
operating systems and processor architectures, firewall and NAT
-
friendly
operation, dynamic address support, and multiple protocol support including
protocol bridging.


There are advantages and disadvantages to

both approaches
.
The principal
advantages of OpenVPN's approach are portability, ease of configuration, and
compatibility with NAT and dynamic addresses. The learning curve for installing
and using OpenVPN is on par with that of other security
-
related daemon
software such as SSH.


Network+ Guide to Networks, 5
th

Edition

Network+ Guide to Networks, 5
th

Edition

The End