NCS315/TEL550 Networking of Information Systems & Advanced - - PowerPoint PPT Presentation

NCS315/TEL550 Networking of Information Systems & Advanced Networking Standards & Protocols Ronny L. Bull, MS Lecturer Computer Science Department Spring 2014

Wireless Review

• 2 types of networks

– Infrastructure – Ad-Hoc

• What are the characteristics of each?
• Why would you use one over the other?

Wireless Review

• Hidden Terminal Problem

A B C

Wireless Review

• Signal Attenuation

A B C

A’s signal strength

space

C’s signal strength

Wireless Review

• Basic Service Set

– Infrastructure mode:

• Contains wireless hosts and AP's

– Ad-Hoc mode:

• Hosts only

Wireless Review

• 802.11b

– 2.4GHz – 2.485GHz – Divided into 11 channels – Channel set by AP admin – Interference with other nearby AP's on same channel

• Solution: stagger channels!
• 1 – 5 – 11

Wireless Review

• Host must associate with AP

– Scans channels, listening for beacon frames

• Contain AP's name (SSID) and MAC
• Selects AP to associate with
• Authenticates if necessary
• Pull DHCP address (if configured)

Wireless Review

AP 2 AP 1 H1 BBS 2 BBS 1

1 2 3 1

passive scanning:

(1)beacon frames sent from APs (2)association Request frame sent: H1 to selected AP (3)association Response frame sent from selected AP to H1

AP 2 AP 1 H1 BBS 2 BBS 1

1 2 2 3 4

active scanning:

(1) Probe Request frame broadcast from H1 (2) Probe Response frames sent from APs (3) Association Request frame sent: H1 to selected AP (4) Association Response frame sent from selected AP to H1

Wireless Review

• CSMA/CA

– Sender

• Senses channel to see if idle
• Transmits entire frame
• If busy back off

– Start random timer – If idle after timer expires transmit – Else set new random timer

Wireless Review

• CSMA/CA

– Receiver

• Receives frame
• Sends ACK to sender

– Helps with hidden terminal problem

Wireless Review

• RTS (Request To Send)

– Sender transmits small RTS packet to reserve channel – May collide with other RTS packets

• CTS (Clear To Send)

– BS broadcasts CTS in response to RTS – Heard by all nodes

Wireless Review

AP A B time R T S ( A ) R T S ( A ) CTS(A) CTS(A) DATA (A) ACK(A) ACK(A) reservation collision defer

Wireless Review

frame control duration address 1 address 2 address 4 address 3 payload CRC

2 2 6 6 6 2 6 0 - 2312 4

seq control

Address 2: MAC address

• f wireless host or AP

transmitting this frame Address 1: MAC address

• f wireless host or AP

to receive this frame Address 3: MAC address

• f router interface to

which AP is attached Address 4: used

• nly in ad hoc

mode

Wireless Review

frame control duration address 1 address 2 address 4 address 3 payload CRC

2 2 6 6 6 2 6 0 - 2312 4

seq control Type From AP Subtype To AP More frag WEP More data Power mgt Retry Rsvd Protocol version

2 2 4 1 1 1 1 1 1 1 1 duration of reserved transmission time (RTS/CTS) frame seq # (for RDT) frame type (RTS, CTS, ACK, data)

Wireless Review

• 802.15 (Bluetooth)

– Less than 10m diameter – Replacement for cables (mouse, keyboard) – Ad-hoc – Master/slaves – 2.4-2.5 GHz – Up to 721 kbps

Multimedia Review

time audio signal amplitude analog signal quantized value of analog value quantization error sampling rate (N sample/sec)

Multimedia Review

• If a sample of audio is taken from a stereo source at

44,100 samples per second for 1 hour what is the amount of disk space required to store the resulting file?

• Formula

– Samples per second * bits per sample * number of channels = total bps required for storage – Total bps required / 8 = total bytes per second – Total Bps required * 60 = total Bpm – Total Bpm * 60 = total Bph – Bph/1000 = KBph/1000 = MBph

Multimedia Review

• If a sample of audio is taken from a stereo source at

44,100 samples per second for 1 hour what is the amount of disk space required to store the resulting file?

• Using a resolution of 16 bits per sample

– 44,100 * 16 * 2 = 1,411,200 bits required per second

– 1,411,200/8 = 176400 bytes required per second – 176400 * 60 = 10584000 bytes required per minute

Multimedia Review

– 10584000 * 60 = 635040000 bytes required per hour – 635040000/1000 = 635040 Kilobits per hour – 635040/1000 = 635.04 Megabytes per hour – To store 1 hour of stereo audio would take up 635.04 Mb of disk space.

Multimedia Review

• Audio / Video applications

– Streaming: can begin playout before downloading entire file – Stored (at server): Can transmit faster than audio/video will be rendered. – Conversational

• Voice/video over IP
• Low delay requirement

– Live streaming

Multimedia Review

• 1. video

recorded (e.g., 30 frames/sec )

• 2. video

sent Cumulative data streaming: at this time, client playing out early part of video, while server still sending later part of video network delay (fixed in this example) time

• 3. video received,

played out at client (30 frames/sec)

Multimedia Review

• Once client playout begins, playback must match
• riginal timing

– Network delays are variable

• Jitter
• Latency

– Need client side buffer to match playout requirements

Multimedia Review

constant bit rate video transmission Cumulative data time variable network delay client video reception constant bit rate video playout at client client playout delay

buffered video

Multimedia Review

1

• 1. Bob manages

Netflix account Netflix registration, accounting servers Amazon cloud Akamai CDN Limelight CDN Level-3 CDN 2

• 2. Bob browses

Netflix video 3

• 3. Manifest file

returned for requested video

• 4. DASH

streaming upload copies of multiple versions

• f video to CDNs

VoIP Review

• Terms you should be familiar with:

– Voice over IP – Video over IP – Convergence – Codecs – ATA – IP-PBX – Hosted PBX

VoIP Review

• More Terms

– IP Telephone

• Softphones
• Hardphones

– Video conferencing

• Video bridge

– Voice conferencing

• Voice bridge

VoIP Review

• H.323

– H.323 terminal – H.323 gateway – H.323 gatekeeper – MCU (multipoint control unit) – H.323 zone

VoIP Review

VoIP Review

• H.225 and H.245 signaling protocols

– Operate at Session layer – H.225 → call or video conferencing signal – H.245 → ensures correct information type formatting

• H.323 standard

– Specifies protocol interoperability

VoIP Review

• SIP (Session Initiation Protocol)

– Similar to H.323 – Modeled on HTTP (Clear text) – Components

• User agent
• User agent client
• User agent server
• Registrar server
• Proxy server
• Redirect server

VoIP Review

VoIP Review

• RTP

– Application layer protocol – Relies on UDP at transport layer – Applies sequence numbers

• Destination packet assembly order
• Packet loss during transmission

– Assigns packet timestamp

• Receiving node
• Compensates for delay
• Signal sync

VoIP Review

• RTCP

– Provides quality feedback to participants – Not mandatory on RTP networks – RTP and RTCP

• Provide information about packet order, loss,

delay

• Cannot correct transmission flaws

VoIP Review

• QoS (Quality of Service)

– Helps to prevent delays, disorder, and distortion – RSVP & Diffserv

VoIP Review

• RSVP (Resource Reservation Protocol)

– Transport layer protocol

• Reserves network resources prior to

transmission – Creates path between sender & receiver

• Provides sufficient bandwidth
• Same path followed in reverse

– Two types of service

• Guaranteed service
• Controlled-load service

VoIP Review

• RSVP

– Emulates circuit-switched path

• Provides excellent QoS

– Drawback: high overhead

• Good for small networks
• Bad for large networks

VoIP Review

• DiffServ

– Prioritizes traffic

• Different streams can get different priorities

– Modifies actual datagram – Accounts for all network traffic

VoIP Review

• EF (Expedited Forwarding)
• Data stream assigned minimum departure rate
• Circumvents delays
• AF (Assured Forwarding)
• Data streams assigned different router

resource levels

• Prioritizes data handling
• No guarantee of on time, in sequence arrival

Network Security Review

• Terms you should know

– Security Assessment

• Posture assessment

– Hacker – Cracker – Vulnerability – Exploit

• 0-day

Network Security Review

• Human Risks

– Social engineering – Error – Ignorance – Omissions

• Easiest way to circumvent network security

– Take advantage of human error

Network Security Review

• What are some other risks associated with the

security of a network?

• How can one find and exploit these?
• Where do most network security compromises occur

from?

• What is a security policy? Why is it important?
• What does not belong in a security policy?

Network Security Review

• Physical security
• Secure network design
• ACL's
• IDS/IPS
• Firewalls
• DMZ
• Honeypots
• NIPS/HIPS
• Proxy Servers
• Network Scanners

Network Security Review

• Network Operating System Security

– What are some things we can do to lock it down?

• Login restrictions
• Password rules
• Group Policy
• Access restrictions

Network Security Review

• Encryption

– Symmetric

• Shared Key

– Asymmetric

• Private/Public Key
• Digital Certificates
• SSL
• SSH
• IPSec

Network Security Review

• Authentication

– Radius – TACACUS+ – PAP – CHAP / MS-CHAP – EAP (802.1x EAPoL) – Kerberos

Network Security Review

• Wireless

– WEP – WPA – 802.11i (802.1x (EAPoL)

Integrity & Availability Review

• Terms

– Integrity – Availability – Uptime – Malware – Virus – Trojan – Polymorphism

Integrity & Availability Review

• Failures and faults

– How do we cope with them?

• Environment

– Heating and cooling

• Power

– Blackout – Brownout – Surge – Noise

Integrity & Availability Review

• Redundancy

– Power – Data

• RAID
• NAS/SAN

– Network

• Physical topology

– Service redundancy & load balancing

• DNS tricks
• Clustering
• Mirroring

Integrity & Availability Review

• Data backup

– Media types – Incremental – Full – Differential – Grandfather-Father-Son

• Disaster recovery planning

– Cold site – Warm site – Hot site

Network Management Review

• Documentation

– Topology – Devices – Configurations – Changes!

• Baselining
• Policies, Proceedures & Regulations

– HIPPA – CALEA – FERPA

Network Management Review

• Network Monitoring

– SNMP – MIB – Alerts & Alarms – Nagios & Cacti

• System and Event Logging

– Event Viewer – Syslog & Journald

Network Management Review

• Traffic shaping

– Limiting – Prioritization

• Delay less important traffic
• Base on protocol, IP, groups, etc..

– Block traffic

• Caching

– DNS – Web

Network Management Review

• Asset management

– Documentation – Asset tracking – Inventory

• Software/NOS changes

– Steps to update or upgrade – Reversing changes – Backleveling

• Physical network changes

Network Management Review

• DOCUMENT EVERYTHING!!!!!

Network Troubleshooting Review

• Is it broke?
• Is it plugged in?
• Is it turned on?
• Who touched it last?
• Point finger
• Fix it... fix it... fix it... fix it... NOW!!!!

Network Troubleshooting Review

• Troubleshooting steps

– Identify problem – Establish theory of probable cause – Test theory to determine cause – Establish action plan – Implement solution or escalate – Verify full functionality – Implement preventative measures – Document findings, actions, and

• utcomes

Subnetting Review

• Practice questions from review sheets
• Look at http://subnettingquestions.com for more

practice questions

Other Tidbits

• Final exam will only cover material from after the

midterm

• Review quizzes 5, 6&7
• Final exam date

– Mon 5/5 12:45p – 2:45p in A115 – Online students must come to campus at that time

• r arrange for a proctor.