Computer Networks Ivan Marsic Rutgers University Chapter 7 – Network Security Chapter 8 –...

Computer Networks

Ivan Marsic

Rutgers University

Chapter 7 – Network SecurityChapter 8 – Network Monitoring

Chapter 9 – Internet ProtocolsAPPENDIX: Probability Refresher

Network Security

Chapter 7

Topic:Secure Communication

Network Security Problem Symmetric and Public-Key Cryptosystems Cryptographic Algorithms Authentication

4

Network Security Problem

Sender Receiver

Padlockand sharedkey copy

Sharedkey copy

Content

MessageIntermediary

Threats posed by intruder/adversary:• forge the key and view the content• damage/substitute the padlock• damage/destroy the message• observe characteristics of messages

(statistical and/or metric properties)

Receiver needs:• receive securely a shared key copy• positively identify the message sender • detect any tampering with messages

Sender needs:• receive securely a copy of the shared key • positively identify the message receiver

Secure/Confidential Communication ?

Objectives of Information Security

• Confidentiality: information not disclosed or revealed to unauthorized persons

• Integrity: consistency of data—preventing unauthorized creation, modification, or destruction

• Availability: legitimate users are not unduly denied access to resources, including information resources, computing resources, and communication resources

• Authorized use: resources are not used by unauthorized persons or in unauthorized ways

Message Encoding and Decoding

• Encoding takes a message M and produces a coded form f(M)

• Decoding the message requires an inverse function , such that = M. )(1 Mff

Two Basic Types of Cryptosystems

• Symmetric systems: both parties use the same (secret) key in encryption and decryption transformations

• Public-key systems (aka asymmetric systems): the parties use two related keys, one of which is secret and the other can be publicly disclosed

Public-Key Cryptosystem

8

Sender Receiver

1. Sender secures the briefcasewith his/her padlock and sends

2. Receiver additionally securesthe briefcase with his/herpadlock and returns

3. Sender removes his/herpadlock and sends again

4. Receiver removes his/herpadlock to access the content

Sender’spadlock

Receiver’spadlock

Public-Key Cryptosystem - mod

9

Sender

Receiver

Receiver distributes his/her padlock (unlocked)to sender ahead of time, but keeps the key

Sender uses the receiver’s padlockto secure the briefcase and sends

Receiver removes his/herpadlock to access the content

Receiver’spadlock (unlocked)

Receiver’skey

“Public key” “Private key”

Public-Key Cryptography

In RSA, receiver does the following:

• Randomly select two large prime numbers p and q, which always must be kept secret.

• Select an integer number E, known as the public exponent, such that (p 1) and E have no common divisors, and (q 1) and E have no common divisors.

• Determine the product n = pq, known as public modulus.

• Determine the private exponent, D, such that (ED 1) is exactly divisible by both (p 1) and (q 1). In other words, given E, we choose D such that the integer remainder when ED is divided by (p 1)(q 1) is 1.

• Release publicly the public key, which is the pair of numbers n and E, K = (n, E). Keep secret the private key, K = (n, D).

Example: send the plaintext “hello world”

• receiver chooses p = 5 and q = 7• receiver chooses E = 5, because 5 and (5 1)(7

1) have no common factors. Also, n = pq = 35

• receiver chooses D = 29, because

i.e., they are exactly divisible. • receiver’s public key is K = (n, E) = (35, 5),

which is made public. The private key K = (n, D) = (35, 29) is kept secret.

624144

641295

)1()1(1

qp

DE

Example, cont’d

Plaintext letterPlaintext numeric

representationBE Ciphertext BE % n

h 8 85 = 32768 85 % 35 = 8

e 5 55 = 3125 55 % 35 = 10

l 12 125 = 248832 125 % 35 = 17

l 12 248832 17

o 15 155 = 759375 155 % 35 = 15

Ciphertext CD B = CD % n Plaintext letter

8 829 = 154742504910672534362390528 829 % 35 = 8 h

10 100000000000000000000000000000 5 e

17 481968572106750915091411825223071697 12 l

17 481968572106750915091411825223071697 12 l

15 12783403948858939111232757568359375 15 o

Encryption

Decryption

Example, cont’d

• While the adversary knows n and E, he or

she does not know p and q, so they cannot

work out (p 1)(q 1) and thereby find D.

Topic:Authentication

Network Security Problem Symmetric and Public-Key Cryptosystems Cryptographic Algorithms Authentication

Authentication Protocol (1)

Secure communication is not enough … playback attack:

Assumption: Only Sender needs to be authenticated to Receiver, not mutually.

Sender ReceiverAdversary

record

EncryptPK-receiversender-ID, password

ACK

replay EncryptPK-receiversender-ID, password

ACK

Receiver’s public key

Replayed message

Authentication Protocol (2)Solution to playback attack:

Sender ReceiverAdversary

record

EncryptPK-receiversender-ID, password

replay EncryptPK-receiversender-ID, password

Does not know how to reply!


number used once and

never again

EncryptPK-receivernonce1

EncryptPK-sendernonce1

Sender’s public key


ACK

EncryptPK-sendernonce2

Impersonation Attack

PROBLEM: Public key distribution … Adversary impersonates Bank

PROBLEM: Customer unaware that Adversary obtained his account info!

Customer BankAdversary

EncryptPK-adversarycustomer-ID, password, PK-customer

I am Bank and here is my public key

Adversary’s public key

Decrypt Customer’s message and obtain ID & password

EncryptPK-bankcustomer-ID, password, PK-adversary

Bank’s public key

Assumption:Adversary obtained Bank’s public key

Adversary’s public keyCustomer’s

public key

EncryptPK-adversarycustomer-account-infoDecrypt Bank’s message and obtain Customer account info

EncryptPK-customercustomer-account-info

Customer’s public key

Network Monitoring

Chapter 8

Packet-pair Dispersion

Router 1 Router 2Link 1Link 2

Link 3

Sendpacket

pair

Receivepacket

pair

t2 t1t4 t3

t4 t3

Pkt-1P1P2

Pkt-1Pkt-2Pkt-2Pkt-2

Packets

Minimum packet spacing at bottleneck link

Same spacing is preserved on higher speed links= Time to process P bytes packet

P

Link speed estimation = P/

Flow direction

t1 t2 t3 t4

Internet Protocols

Chapter 9

The Internet Reference Model

http://en.wikipedia.org/wiki/OSI_model

Visit http://en.wikipedia.org/wiki/Internet_reference_model for more details on the Internet reference model

IPv6 Header0 11 12 313 4 15 16

20-bit flow label

16-bit payload length 8-bit hop limit

versionnumber

40bytes

8-bit traffic class

next header

128-bit (16-byte) destination IP address

128-bit (16-byte) source IP address

IPv6 Address Prefix Assignments

11111111

Unspecified

Loopback within this network

Multicast addresses

Link-local use unicast

127

127

127

127

0

00000000 ... 00000000

0

1270

9 100

11111110 10

0

00000000 ... 00000001

7 8

Anything

Anything

Site-local use unicast 11111110 11 Anything9 10

Everything elseGlobal unicast

1270

00000000Reserved

1270 7 8

Anything

IPv4 compatible address(Node supports IPv6 & IPv4)

127

1270 95 96

0

00000000 ... 00000000

000000 ... 000000IPv4 mapped address(Node does not support IPv6)

111...11

IPv4 Address

IPv4 Address

95 96

79 80

IPv6 Global Unicast Address

global routing prefixIPv6 global unicast address

general format

1270 (n bits) (m bits) (128 n m bits)

subnet ID interface ID

global routing prefixIPv6 global unicast address

format for prefix not “000”

1270 (n bits) (64 bits)(64 n bits)

subnet ID interface ID

(b)

(a)

Example IPv6 Extension Headers

application data payload

IPv6 main header

Hop-by-hopoptions header

Routing header

Fragment header

Destinationoptions header

TCP header

MandatoryIPv6 header

Optionalextension

headers

IPv6 packetpayload

40 bytes

variable

variable

variable

8 bytes

20 bytes (default)

variable

= Next Header field

Format of IPv6 Extension Headers

0 15 16 317 8

Hdr ext len

One or more options

Reserved

0 15 16 317 8

(a) Hop-by-Hop Options header;Destinations Options header

(b) Fragment header

Next headerNext header

Next headerNext header MRes

28 29

Fragment offset

Identification

0 15 16 31

Type-specific data

23 24

Segments left

(c) Generic Routing header


7 8

Hdr ext len Routing type

0 15 16 317 8

Hdr ext len

One or more options

Reserved

0 15 16 317 8

(a) Hop-by-Hop Options header;Destinations Options header

(b) Fragment header


Next headerNext header MRes

28 29

Fragment offset

Identification

0 15 16 31

Type-specific data

23 24

Segments left

(c) Generic Routing header


7 8

Hdr ext len Routing type

0 7 8


Reserved

(d) Type 0 Routing header

Address[n]

15 16 3123 24

Segments leftHdr ext len 0

Address[1]

Address[2]

0 7 8


Reserved

(d) Type 0 Routing header

Address[n]

15 16 3123 24

Segments leftHdr ext len 0

Address[1]

Address[2]

RIP Header (for IPv4)

Total up to 25 route entries

0 15 16 317 8

version unused (must be zero)

address family identifier

distance metric

IPv4 address

route tag

command

next hop

subnet mask16

bytes

8bytesRIP header

RIP route entry

Total up to 25 route entries

0 15 16 317 8

version unused (must be zero)

address family identifier

distance metric

IPv4 address

route tag

command

next hop

subnet mask16

bytes

8bytesRIP header

RIP route entry

OSPF Directed Graph of an AS

AAN1

N2

BB

CC

DD

H2

N3AS

AS

H1 1

2

1

1

5

3

1

8

6

7

4

N1

A

B

C

D

N3N2

H2

12

1

57

1

3

6

8

14

(a)

(b)

OSPF Header (for IPv4)

OSPF packet payload

0 15 16 317 8

type packet length

area ID

version

authentication

24bytesOSPF header

checksum authentication type

source router address (IPv4 )

OSPF - LSA Header0 15 16 317 8

LS age

LS sequence number

authentication

20bytesLSA header

LS checksum length

link state ID

typeoptions

link ID

link data

link type num_TOS metric

optional TOS information

Link descriptionfor LSA type = 1

(more link descriptions)

16bytes

0 0 number of linksflags

eBGP and iBGP Sessions

AS AS

LL

KK

NN

PP

OO QQ

MM

AS

AS

HH

JJ

II

AA

FF

BB

GG

DD

CC

EE

Link-layer connection

eBGP TCP session

Key:

iBGP TCP session

Link-layer connection

eBGP TCP session

Key:

iBGP TCP session

BGP Finite State Machine

ManualStart ORAutomaticStart /

ManualStop /

ConnectRetryTimerexpired / retry

DelayOpenTimer expires ORDelayOpen attribute == FALSE /

ManualStop OR AutomaticStop ORHoldTimer expired /

send NOTIFICATION cease

OPEN or msg recvd / send KEEPALIVE msg

KEEPALIVEmsg recvd /

ManualStop OR AutomaticStop OR Error in msg detected ORNOTIFICATION error recvd /

KEEPALIVE orUPDATE msg recvd /

TcpConnectionFails /

Idle

Established

Setting upTCP connection

{Connect, Active}

OpeningBGP session

{OpenSent, OpenConfirm}

Detail from Figure 1-49:

NN

RR

SS

AS

AS

{AS

{AS, A

S, A

S}}

{AS

{AS, A

S, A

S}}

{{CustCust}}{{CustCust}}

AS

BGP Header & Message Formats

(a) BGP header format

0 15 16 3123 24

MarkerMarker

LengthLength TypeType

0 7 8 15 16 3123 24

MarkerMarker

LengthLength Type: OPENType: OPEN VersionVersion

My autonomous systemMy autonomous system Hold timeHold time

BGP identifierBGP identifier

Optional parameters (variable)Optional parameters (variable)

Optional Optional paramsparamslengthlength

(b) BGP OPEN message format

(c) BGP KEEPALIVE message format

0 15 16 3123 24

MarkerMarker

LengthLengthType:Type:

KEEPALIVEKEEPALIVE

0 7 8 15 16 3123 24

MarkerMarker

LengthLength Error codeError code

Data (variable)Data (variable)Error Error subcodesubcode

(d) BGP NOTIFICATION message format

Type:Type:NOTIFICATIONNOTIFICATION

BGP UPDATE Message

0 7 8 15 16 3123 24

MarkerMarker

LengthLength Type: Type: UPDATEUPDATE

Withdrawn routes (variable)Withdrawn routes (variable)

Withdrawn routes lengthWithdrawn routes length

Path attributes (variable)Path attributes (variable)

Total path attribute lengthTotal path attribute length

Network layer reachability information (variable)Network layer reachability information (variable)

(a) BGP UPDATE message format (c) Attribute type format

Attribute type (2 bytes)Attribute type (2 bytes) Attrib. length (1 or 2 bytes)Attrib. length (1 or 2 bytes)

Attribute value (variable)Attribute value (variable)

(b) Path attribute format

Attributetype codeO T P E 0

Attribute flags

OptionalTransitive

PartialExtended Length

Example BGP UPDATE Message

AS AS

LL

KKNN

AS

OO

MM

Subnet Prefix =128.34.10.0/24

192.12.69.2

Prefix = 128.34/16

Prefix = 128.34/16

AS_PATH = {AS

AS_PATH = {AS}}

NEXT_HOP = 192.12.69.2

NEXT_HOP = 192.12.69.2

UPDATE

192.12.69.1

Prefix = 128.34/16

Prefix = 128.34/16

AS_PATH = {

AS_PATH = {ASAS, , ASAS}}

NEXT_HOP = 192.12.62.1

NEXT_HOP = 192.12.62.1UPDATE

192.12.62.1

192.12.62.2

128.34.10.0/24 192.12.69.2

Prefix Next Hop

K’s forwarding table:

128.34.10.0/24 192.12.50.5

Prefix Next Hop

N’s forwarding table:

128.34.10.0/24 192.12.62.1

Prefix Next Hop

O’s forwarding table:

AS BGP routing table:

128.34.10.0/24 192.12.69.2

Prefix Next HopPath

{AS}

K’s IGP routing table:

128.34.10.0/24 0

Destination Cost

KK’’ss BGPBGP

Next Hop

+

192.12.50.5

+AS BGP routing table

N’s IGP routing table:

128.34.10.0/24 2

Destination Cost Next Hop

Router M

Router K 2 Router M

AS AS

LL

KKNN

AS

OO

MM

Subnet Prefix =128.34.10.0/24

192.12.69.2

Prefix = 128.34/16

Prefix = 128.34/16

AS_PATH = {AS

AS_PATH = {AS}}

NEXT_HOP = 192.12.69.2

NEXT_HOP = 192.12.69.2

UPDATE

Prefix = 128.34/16

Prefix = 128.34/16

AS_PATH = {AS

AS_PATH = {AS}}

NEXT_HOP = 192.12.69.2

NEXT_HOP = 192.12.69.2

UPDATE

192.12.69.1

Prefix = 128.34/16

Prefix = 128.34/16

AS_PATH = {


NEXT_HOP = 192.12.62.1


Prefix = 128.34/16

Prefix = 128.34/16

AS_PATH = {


NEXT_HOP = 192.12.62.1


192.12.62.1

192.12.62.1

192.12.62.2

128.34.10.0/24 192.12.69.2

Prefix Next Hop


128.34.10.0/24 192.12.69.2

Prefix Next Hop


128.34.10.0/24 192.12.50.5

Prefix Next Hop


128.34.10.0/24 192.12.50.5

Prefix Next Hop


128.34.10.0/24 192.12.62.1

Prefix Next Hop


128.34.10.0/24 192.12.62.1

Prefix Next Hop



128.34.10.0/24 192.12.69.2

Prefix Next HopPath

{AS}


128.34.10.0/24 192.12.69.2

Prefix Next HopPath

{AS}


128.34.10.0/24 0

Destination Cost

KK’’ss BGPBGP

Next Hop


128.34.10.0/24 0

Destination Cost

KK’’ss BGPBGP

Next Hop

+

192.12.50.5

192.12.50.5

+AS BGP routing table


128.34.10.0/24 2


Router M

Router K 2 Router M


128.34.10.0/24 2


Router M

Router K 2 Router M

BGP MULTI_EXIT_DISC (MED) Attribute

AS

AS

AS

AS

AS LL

KKNN

HH

MM

AA

FF

BB

GG

DD

CC

EE

AS

AS

AS

Pref

ix= so

me

pref

ix in

AS

Pref

ix= so

me

pref

ix in

AS

AS_P

ATH

= {

AS_P

ATH

= {A

SAS,

, ASAS}}

ME

D =

300

ME

D =

300

UP

DA

TE

Prefix=

some p

refix i

n AS

Prefix=

some p

refix i

n AS

AS_PATH =

{

AS_PATH =

{ASAS, , A

SAS}}

MED =

100

MED =

100UPDATE

AS

AS

AS

AS

AS LL

KKNN

HH

MM

AA

FF

BB

GG

DD

CC

EE

AS

AS

AS

Pref

ix= so

me

pref

ix in

AS

Pref

ix= so

me

pref

ix in

AS

AS_P

ATH

= {

AS_P

ATH

= {A

SAS,

, ASAS}}

ME

D =

300

ME

D =

300

UP

DA

TEPr

efix=

som

e pr

efix

in AS

Pref

ix= so

me

pref

ix in

AS

AS_P

ATH

= {

AS_P

ATH

= {A

SAS,

, ASAS}}

ME

D =

300

ME

D =

300

UP

DA

TE

Prefix=

some p

refix i

n AS

Prefix=

some p

refix i

n AS

AS_PATH =

{

AS_PATH =

{ASAS, , A

SAS}}

MED =

100

MED =

100UPDATE

Prefix=

some p

refix i

n AS

Prefix=

some p

refix i

n AS

AS_PATH =

{

AS_PATH =

{ASAS, , A

SAS}}

MED =

100

MED =

100UPDATE

Address Resolution Protocol (ARP)

Need for multiple addresses, hierarchical vs. non-hierarchical

1P3BP49K7J F1119661P3BP49K7J F111966

Vehicle identification number (VIN)

Registration plate

Address Resolution Protocol (ARP)

Target

IP: 192.200.96.23MAC: A3-B0-21-A1-60-35

IP: 192.200.96.22MAC: 00-01-03-1D-CC-F7

Sender

IP: 192.200.96.21MAC: 01-23-45-67-89-AB

IP: 192.200.96.20MAC: 49-BD-2F-54-1A-0F

Sender MAC: 01Sender MAC: 01--2323--4545--6767--8989--ABABSender IP: 192.200.96.21Sender IP: 192.200.96.21Target IP: Target IP: 192.200.96.23192.200.96.23

ARP Request: to FF-FF-FF-FF-FF-FF

Sender MAC: 01Sender MAC: 01--2323--4545--6767--8989--ABABSender IP: 192.200.96.21Sender IP: 192.200.96.21Target IP: Target IP: 192.200.96.23192.200.96.23

ARP Request: to FF-FF-FF-FF-FF-FF

Sender MAC: Sender MAC: A3A3--B0B0--2121--A1A1--6060--3535Sender IP: 192.200.96.23Sender IP: 192.200.96.23Target MAC: 01Target MAC: 01--2323--4545--6767--8989--ABABTarget IP: 192.200.96.21Target IP: 192.200.96.21

ARP Reply

Sender MAC: Sender MAC: A3A3--B0B0--2121--A1A1--6060--3535Sender IP: 192.200.96.23Sender IP: 192.200.96.23Target MAC: 01Target MAC: 01--2323--4545--6767--8989--ABABTarget IP: 192.200.96.21Target IP: 192.200.96.21

ARP Reply

ARP Packet Format (for IPv4)

0 15 16 317 8

Protocol addr len = 4

Protocol type = 0x0800Hardware type = 1

Target hardware address (6 bytes)

Sender hardware address (6 bytes)

Target protocol address

Hardware addr len = 6

Sender protocol address (last 2 bytes)

Sender protocol address (first 2 bytes)28

bytes

Operation

Mobile IP

Correspondent node (CN)

Mobile node (MN)

Home Agent (HA)

1

2

3

4

Foreign Agent (FA)

SNMP

Managed device

MIBMIB

Network management system (NMS)

Messages

SNMP manager (client)

SNMP manager (client)

SNMP agent

(server)

SNMP agent

(server)

(a)

(b)

Network

Agent

Managedobjects

GetRequest

GetNextRequest

ResponseResponse

ResponseResponse

GetBulkRequest

SetRequest

ResponseResponse

ResponseResponse

TrapTrap

InformRequestInformRequestInformRequestInformRequestNMS

Probability Refresher

Appendix

Jar with Black & White Balls

Random Events

Possible outcomes of two coin tosses:

“Tree diagram” of possible outcomes of two coin tosses:

HH HT

TH TT

HH HT

TH TT

H T

H

T

First toss

Second toss

First toss

Second toss Outcome

HH

HT

TH

TT

H

T

T

H

½½

½½

½

½

H

T

(a) (b)

Drawing from Jar/Urn Decided by Rolling a Die

JarJar UrnUrn

EXPERIMENT 1:Roll a die; if outcome is 1 or 2, select Jar; else, select Urn

EXPERIMENT 2:Draw a ball from the selected container

Probability Matrix for Ball Drawing

n12

n22

y1 = Jar

y2 = Urn

x1 = Black x2 = White

n11

c2

n21

r1Random variable Y:Identity of the vessel

that will be chosen

Random variable X: Color of the ball

Illustration for Bayes Theorem

JarJar UrnUrn

EXPERIMENT 1:Roll a die; if outcome is 1 or 2, select Jar; else, select Urn

EXPERIMENT 2:Draw a ball from the selected container

Guess whether the ball was drawn from

Jar or from Urn

Poisson Process

average arrival rate = 5

0

5

10

15

20

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

arrivals per time unit (n)

pe

rce

nt

of

oc

cu

rre

nce

s (

%)

Partitioning of Areas Under Normal Curve

0

34.13% 34.13%

2 3 4 2 3 4

13.59% 13.59%

2.15%2.15%0.13%0.13%

0.4

0.3

0.2

0.1

0.0

0

34.13% 34.13%

2 3 4 2 3 4

13.59% 13.59%

2.15%2.15%0.13%0.13%

0.4

0.3

0.2

0.1

0.0

Areas between selected points under the normal curve

How to Read Table A-1

0

Area between mean and z(from Column B)

1 1 2 3 4 2 3 4

z = 1.50(in Column A)

43.32%

0.4

0.3

0.2

0.1

0.0

Area beyond z(from Column C)

6.68%6.68%

0

Area between mean and z(from Column B)

1 1 2 3 4 2 3 4

z = 1.50(in Column A)

43.32%

0.4

0.3

0.2

0.1

0.0

Area beyond z(from Column C)

6.68%6.68%

(A) z

(B) area

between mean and z

(C) area

beyond z

(A) z

(B) area

between mean and z

(C) area

beyond z

(A) z

(B) area

between mean and z

(C) area

beyond z

0.00 .0000 .5000 0.55 .2088 .2912 1.10 .3643 .1357 0.01 .0040 .4960 0.56 .2123 .2877 1.11 .3665 .1335 0.02 .0080 .4920 0.57 .2157 .2843 1.12 .3686 .1314 0.34 .1331 .3669 0.89 .3133 .1867 1.44 .4251 .0749 0.35 .1368 .3632 0.90 .3159 .1841 1.45 .4265 .0735 0.36 .1406 .3594 0.91 .3186 .1814 1.46 .4279 .0721 0.37 .1443 .3557 0.92 .3212 .1788 1.47 .4292 .0708 0.38 .1480 .3520 0.93 .3238 .1762 1.48 .4306 .0694 0.39 .1517 .3483 0.94 .3264 .1736 1.49 .4319 .0681 0.40 .1554 .3446 0.95 .3289 .1711 1.50 .4332 .0668 0.41 .1591 .3409 0.96 .3315 .1685 1.51 .4345 .0655 0.42 .1628 .3372 0.97 .3340 .1660 1.52 .4357 .0643 0.43 .1664 .3336 0.98 .3365 .1635 1.53 .4370 .0630 0.44 .1700 .3300 0.99 .3389 .1611 1.54 .4382 .0618 0.45 .1736 .3264 1.00 .3413 .1587 1.55 .4394 .0606 0.46 .1772 .3228 1.01 .3438 .1562 1.56 .4406 .0594 0.47 .1808 .3192 1.02 .3461 .1539 1.57 .4418 .0582 0.48 .1844 .3156 1.03 .3485 .1515 1.58 .4429 .0571 0.49 .1879 .3121 1.04 .3508 .1492 1.59 .4441 .0559 0.50 .1915 .3085 1.05 .3531 .1469 1.60 .4452 .0548 0.51 .1950 .3050 1.06 .3554 .1446 1.61 .4463 .0537 0.52 .1985 .3015 1.07 .3577 .1423 1.62 .4474 .0526 0.53 .2019 .2981 1.08 .3599 .1401 1.63 .4484 .0516 0.54 .2054 .2946 1.09 .3621 .1379 1.64 .4495 .0505

(A)

z

(B)area

between mean and z

(C)area

beyondz

1.50 .4332 .0668

(A)

z

(B)area

between mean and z

(C)area

beyondz

(A)

z

(B)area

between mean and z

(C)area

beyondz

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Computer Networks Ivan Marsic Rutgers University Chapter 7 – Network Security Chapter 8 –...

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Transcript of Computer Networks Ivan Marsic Rutgers University Chapter 7 – Network Security Chapter 8 –...