1/28/2010 Network Plus Troubleshooting and VOIP

Network+ Guide to Networks, 5 th Edition4 Troubleshooting Methodology (cont’d.) Troubleshooting steps 1.Identify symptoms, problems 2.Identify affected area 3.Determine what has changed 4.Establish most probable cause 5.Determine if escalation necessary 6.Create action plan, solution 7.Implement solution, test result 8.Identify results, effects 9.Document solution, process

Network+ Guide to Networks, 5 th Edition18 Hardware Troubleshooting Tools Utilities help troubleshoot network problems –Specialized tools Crossover cable Butt Set Tone Generator Multimeter Cable Continuity tester TDR OTDR

Software Tools Command line utilities IPCONFIG, Ping, TRACERT, NetStat, NSLookup Network Monitor –Network adapter must support promiscuous mode Plug into port configured for port mirroring –Common terms for abnormal data patterns, packets Local collisions Late collisions Runts Giants Jabber Ghosts

Software Tools Protocol Analyzer –Captures traffic, analyzes frames –Sniffer (packet sniffer) hardware –May require Port Mirroring on switches to see all traffic. Only sees broadcasts and packets directed to the analyzer.

Question 1 When Jeff, a technician, is troubleshooting a problem, which of the following is the NEXT step after verifying full system functionality? –A.Establish a plan of action to resolve the problem and identify potential effects. –B.Implement the solution. –C.Establish a theory of probable cause. –D.Document findings, actions, and outcomes

Question 2 Kim, a network technician, is troubleshooting a problem and has just established a plan of action to resolve the problem. Which of the following is the NEXT step in the troubleshooting methodology? –A. Verify full system functionality and if applicable implement preventative measures. –B.Implement the solution or escalate as necessary. –C.Document findings, actions, and outcomes. –D.Establish a theory of probable cause (e.g. question the obvious).

Question 3 Lisa, a technician, is troubleshooting a cable problem. She has checked both ends and suspects an issue 50 yards (46 meters) from the location. Which of the following network tools will confirm this analysis? –A.TDR –B.Protocol analyzer –C.Multimeter –D.Cable crimper

Question 4 A switch in IDF 3 has shut down at 3 p.m. everyday this week. Which of the following network tools should Kim, a technician, use to troubleshoot this problem? –Environmental monitor –Cable Tester –TDR – Loopback plug

Question 5 Which of the following tools would Lisa, a technician, BEST use to trace a wire through an area where multiple wires of the same color are twisted together? –A.Cable tester –B.Toner probe –C.Cable crimper –D.Punch down tool

Question 6 Zach, a technician, wants to test a laptop's NIC for functionality but has no other networking equipment to attach it to. Which of the following would allow him to test basic functionality of the NIC? –A.Loopback plug –B.Protocol analyzer –C.Smart jack – D.Coupler

Question 7 Lisa, a network technician, is troubleshooting a new wireless network that has been dropping connections. She notices another wireless network in the area. Which of the following BEST explains the reason for the dropped connections? –A. Latency –B. SSID mismatch –C. Interference –D. Encryption type

Question 8 Zach, a technician, suspects a duplicate IP address assignment on the network. Which of the following resources can be used to verify this problem? –A. Network map –B. Environmental monitor –C. Placement map –D. Syslog

Question 9 Zach, a technician, discovers a switch is not communicating with the other switches in a stack. Which of the following is the MOST likely cause? –A.Both T568A and T568B standards are being used. –B.STP is disabled. –C.The cable is not a crossover. –D.The port is not trunked.

Question 10 Kim, a network consultant, noticed that a new installation for a network backbone looked like this: ISP - Switch - Firewall - PC. Which of the following is the BEST configuration for a properly setup environment? –A.Switch - ISP - Firewall – PC –B.ISP - Firewall - Switch - PC –C.Firewall - ISP - PC - Switch –D.ISP - PC - Firewall - Switch

VOIP Components

Network+ Guide to Networks, 5 th Edition14 Analog Telephone Attachment Figure 11-4 Integrating VoIP networks and analog telephones

Network+ Guide to Networks, 5 th Edition15 Digital - IP Telephones IP telephones (IP phones) –Transmit, receive only digital signals –Voice immediately digitized, issued to network in packet form –Requires unique IP address –Looks like traditional touch-tone phone Connects to RJ-45 wall jack Connection may pass through connectivity device before reaching IP-PBX

Softphones Computer programmed to act like IP telephone –Softphones and IP telephones Provide same calling functions Connect to network; deliver services differently –Prerequisites Computer minimum hardware requirements IP telephony client installed Digital telephone switch communication Full-duplex sound card Microphone, speakers –Example: Skype Network+ Guide to Networks, 5 th Edition20

Network+ Guide to Networks, 5 th Edition23 Figure 11-8 Connecting softphones to a converged network

Network+ Guide to Networks, 5 th Edition37 Signaling Protocols Signaling –Establish connection –Information exchange Between network components, system Establishing, monitoring, releasing connections Controlling system operations SS7 –Protocol for handling call signaling in PSTN connections H.323 and SIP for VOIP

38 H.323 Supports voice, video-over-IP services H.323 components –H.323 terminal –H.323 gateway –H.323 gatekeeper –MCU (multipoint control unit) –H.323 zone H.323 Protocols –H.225 – Application layer used for call setup signaling –H.245 – Session/presentation layer formatting Logical channels identified as port numbers One channel for each direction (full duplex)

Network+ Guide to Networks, 5 th Edition42 SIP (Session Initiation Protocol) Performs similar H.323 functions Version 2.0 (RFC 2543) –1999 IETF codified Application layer signaling, multiservice control protocol, packet-based networks Goals –Modeled on HTTP protocol –Reuse existing TCP/IP protocols Session management, enhanced services –Modular and specific

Network+ Guide to Networks, 5 th Edition43 SIP (cont’d.) Similar purpose to H.323 –More Limited capabilities and functions Does not supply caller ID SIP network –Modeled on HTTP –Standard maps out terms and architecture User agent User agent client User agent server Registrar server Proxy server Redirect server

Network+ Guide to Networks, 5 th Edition44 SIP (cont’d.) Figure A SIP network

Network+ Guide to Networks, 5 th Edition45 SIP vs H.323 SIP and H.323 –Regulate call signaling, control for VoIP or video-over- IP clients and servers –Do not account for communication between media gateways VoIP vendors prefer SIP over H.323 –Simplicity –Fewer instructions to control call –Consumes fewer processing resources –Adapts easier –More flexible

46 Media Gateways Gateways –Enable converged networks Convert analog to digital signals Translate between SS7 and H.323/SIP MGCP (Media Gateway Control Protocol) MEGACO Performs same functions as MGCP with different commands and processes Operates with H.323 or SIP Superior to MGCP Supports ATM

Network+ Guide to Networks, 5 th Edition48 MGCP and MEGACO (cont’d.) Figure Use of an MGC (media gateway controller)

Transport Protocols Used to deliver voice or video payload Typically use UDP because less overhead Require some additional delivery feedback information and method to provide for Quality of Service (QoS) in Delivery Delivery Feedback Protocols –RTP –RTCP QoS Proocols –RSVP –DiffServ –MPLS

Network+ Guide to Networks, 5 th Edition51 RTP (Real-time Transport Protocol) RFC 1889 –Operates at Application layer –Relies on UDP Applies sequence numbers to indicate: –Destination packet assembly order –Packet loss during transmission Assigns packet timestamp –Receiving node Compensates for network delay, synchronize signals No mechanism to detect success

RTCP (Real-time Transport Control Protocol) Provides quality feedback to participants –Packets transmitted periodically Works with RTP –Not mandatory on RTP networks RTP and RTCP –Provide information about packet order, loss, delay –Cannot correct transmission flaws 52

53 QoS (Quality of Service) Assurance Protocols used to improve the packet switched VOIP or Video connection to make it more like a dedicated PSTN or Cable network. QoS measures how well a service matches its expected performance. –High Does not experience interruptions, distortions, or broken communications –Low May experience communication problems QoS protocols –RSVP –DiffServ –MPLS

54 RSVP (Resource Reservation Protocol) Transport layer protocol Reserves network resources before transmission by creating path between sender, receiver Issues PATH statement via RSVP to receiving node Two service types –Guaranteed service No packet losses – minimal delay –Controlled-load service Type of service typical on low usage network

Network+ Guide to Networks, 5 th Edition57 DiffServ Addresses traffic prioritization QoS issues Differs from RSVP –Modifies actual IP datagram –Accounts for all network traffic To prioritize traffic –IPv4 datagram: DiffServ field –IPv6 datagram: Traffic Class field

58 DiffServ (cont’d.) Two forwarding types –EF (Expedited Forwarding) Data stream assigned minimum departure rate Circumvents delays by setting strict limits – max 30 % of traffic –AF (Assured Forwarding) Data streams assigned different router resource levels Prioritizes data handling but provides not guarantee of On time, in sequence packet arrival Uses AF Classes to provide different service levels

Network+ Guide to Networks, 5 th Edition59 MPLS (Multiprotocol Label Switching) Modifies data streams at Network layer A first router data stream encounters –Replaces IP datagram header with label Packet forwarding information –Router’s data stream path revises label Indicates next hop –Considers network congestion Very fast forwarding: no delay –Destination IP address compared to routing tables Forward data to closest matching node

Network+ Guide to Networks, 5 th Edition The End