Transcript Network+ Guide to Networks 5th Edition

Network Plus
Troubleshooting and VOIP
1/28/2010
1/28/2010
Troubleshooting Methodology (cont’d.)
• Troubleshooting steps
1.
2.
3.
4.
5.
6.
7.
8.
9.
Identify symptoms, problems
Identify affected area
Determine what has changed
Establish most probable cause
Determine if escalation necessary
Create action plan, solution
Implement solution, test result
Identify results, effects
Document solution, process
Network+ Guide to Networks, 5th Edition
4
Hardware Troubleshooting Tools
• Utilities help troubleshoot network problems
– Specialized tools
•
•
•
•
•
•
•
Crossover cable
Butt Set
Tone Generator
Multimeter
Cable Continuity tester
TDR
OTDR
Network+ Guide to Networks, 5th Edition
18
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
Analog Telephone Attachment
Figure 11-4 Integrating VoIP networks and analog telephones
Network+ Guide to Networks, 5th Edition
14
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
Network+ Guide to Networks, 5th Edition
15
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, 5th Edition
20
Figure 11-8 Connecting softphones to a converged network
Network+ Guide to Networks, 5th Edition
23
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
Network+ Guide to Networks, 5th Edition
37
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)
38
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, 5th Edition
42
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, 5th Edition
43
SIP (cont’d.)
Figure 11-14 A SIP network
Network+ Guide to Networks, 5th Edition
44
SIP vs H.323
• SIP and H.323
– Regulate call signaling, control for VoIP or video-overIP 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
Network+ Guide to Networks, 5th Edition
45
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
46
MGCP and MEGACO (cont’d.)
Figure 11-15 Use of an MGC (media gateway controller)
Network+ Guide to Networks, 5th Edition
48
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
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
Network+ Guide to Networks, 5th Edition
51
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
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
53
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
54
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
Network+ Guide to Networks, 5th Edition
57
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
58
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, 5th Edition
59
The End
Network+ Guide to Networks, 5th Edition