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

Transcription

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

2 Wireless Review 2 types of networks Infrastructure Ad-Hoc What are the characteristics of each? Why would you use one over the other?

3 Wireless Review Hidden Terminal Problem C A B

4 Wireless Review Signal Attenuation A B C A s signal strength C s signal strength space

5 Wireless Review Basic Service Set Infrastructure mode: Contains wireless hosts and AP's Ad-Hoc mode: Hosts only

6 Wireless Review b 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!

7 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)

8 BBS 1 BBS 2 BBS 1 BBS 2 AP AP 2 AP AP 2 H1 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 H1 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

9 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

10 Wireless Review CSMA/CA Receiver Receives frame Sends ACK to sender Helps with hidden terminal problem

11 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

12 A AP B RTS(A) RTS(A) reservation collision CTS(A) CTS(A) DATA (A) defer time ACK(A) ACK(A) Wireless Review

13 frame control duration address 1 Wireless Review address 2 address 3 seq control address 4 payload CRC Address 1: MAC address of wireless host or AP to receive this frame Address 2: MAC address of wireless host or AP transmitting this frame Address 3: MAC address of router interface to which AP is attached Address 4: used only in ad hoc mode

14 Wireless Review duration of reserved transmission time (RTS/CTS) frame seq # (for RDT) frame control duration address 1 address 2 address 3 seq control address 4 payload CRC Protocol version Type Subtype To AP From AP More frag 1 1 Power Retry mgt More data WEP Rsvd frame type (RTS, CTS, ACK, data)

15 Wireless Review (Bluetooth) Less than 10m diameter Replacement for cables (mouse, keyboard) Ad-hoc Master/slaves GHz Up to 721 kbps

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

17 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

18 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 = bytes required per second * 60 = bytes required per minute

19 Multimedia Review * 60 = bytes required per hour /1000 = Kilobits per hour /1000 = Megabytes per hour To store 1 hour of stereo audio would take up Mb of disk space.

20 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

21 Cumulative data 1. video recorded (e.g., 30 frames/sec ) 2. video sent network delay (fixed in this example) 3. video received, played out at client (30 frames/sec) time streaming: at this time, client playing out early part of video, while server still sending later part of video Multimedia Review

22 Multimedia Review Once client playout begins, playback must match original timing Network delays are variable Jitter Latency Need client side buffer to match playout requirements

23 Cumulative data constant bit rate video transmission variable network delay client video reception buffered video constant bit rate video playout at client client playout delay time Multimedia Review

24 Amazon cloud upload copies of multiple versions of video to CDNs Akamai CDN Netflix registration, accounting servers 1 2. Bob browses Netflix video Manifest file returned for requested video Limelight CDN 1. Bob manages Netflix account 4. DASH streaming Level-3 CDN Multimedia Review

25 VoIP Review Terms you should be familiar with: Voice over IP Video over IP Convergence Codecs ATA IP-PBX Hosted PBX

26 VoIP Review More Terms IP Telephone Softphones Hardphones Video conferencing Video bridge Voice conferencing Voice bridge

27 VoIP Review H.323 H.323 terminal H.323 gateway H.323 gatekeeper MCU (multipoint control unit) H.323 zone

28 VoIP Review

29 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

30 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

31 VoIP Review

32 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

33 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

34 VoIP Review QoS (Quality of Service) Helps to prevent delays, disorder, and distortion RSVP & Diffserv

35 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

36 VoIP Review RSVP Emulates circuit-switched path Provides excellent QoS Drawback: high overhead Good for small networks Bad for large networks

37 VoIP Review DiffServ Prioritizes traffic Different streams can get different priorities Modifies actual datagram Accounts for all network traffic

38 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

39 Network Security Review Terms you should know Security Assessment Posture assessment Hacker Cracker Vulnerability Exploit 0-day

40 Network Security Review Human Risks Social engineering Error Ignorance Omissions Easiest way to circumvent network security Take advantage of human error

41 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?

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

43 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

44 Network Security Review Encryption Symmetric Shared Key Asymmetric Private/Public Key Digital Certificates SSL SSH IPSec

45 Network Security Review Authentication Radius TACACUS+ PAP CHAP / MS-CHAP EAP (802.1x EAPoL) Kerberos

46 Network Security Review Wireless WEP WPA i (802.1x (EAPoL)

47 Integrity & Availability Review Terms Integrity Availability Uptime Malware Virus Trojan Polymorphism

48 Integrity & Availability Review Failures and faults How do we cope with them? Environment Heating and cooling Power Blackout Brownout Surge Noise

49 Integrity & Availability Review Redundancy Power Data RAID NAS/SAN Network Physical topology Service redundancy & load balancing DNS tricks Clustering Mirroring

50 Integrity & Availability Review Data backup Media types Incremental Full Differential Grandfather-Father-Son Disaster recovery planning Cold site Warm site Hot site

51 Network Management Review Documentation Topology Devices Configurations Changes! Baselining Policies, Proceedures & Regulations HIPPA CALEA FERPA

52 Network Management Review Network Monitoring SNMP MIB Alerts & Alarms Nagios & Cacti System and Event Logging Event Viewer Syslog & Journald

53 Network Management Review Traffic shaping Limiting Prioritization Delay less important traffic Base on protocol, IP, groups, etc.. Block traffic Caching DNS Web

54 Network Management Review Asset management Documentation Asset tracking Inventory Software/NOS changes Steps to update or upgrade Reversing changes Backleveling Physical network changes

55 Network Management Review DOCUMENT EVERYTHING!!!!!

56 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!!!!

57 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 outcomes

58 Subnetting Review Practice questions from review sheets Look at for more practice questions

59 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 or arrange for a proctor.