Transcript C4 CMTS

Telephony Troubleshooting in the
Home
ARRIS/SCTE
www.arrisi.com
SCTE VoIP Home Troubleshooting
Seminar Objectives
▪ Describe the functional role of each component
necessary for operation of a PacketCable VOIP
network.
▪ eMTA installation
▪ List common technical problems associated with a
PacketCable VOIP network
▪ Discuss impact of network problems on voice
quality
▪ Isolate and repair common VoIP problems
2
July 2008
PacketCable Definition
PacketCable is a set of protocols and associated
functional requirements developed to deliver
Quality-of-Service (QoS) enhanced secure
communications services using packetized data
transmission technology to a consumer’s home
over the cable television hybrid fiber coax (HFC)
data network.
3
July 2008
PacketCable VoIP Network Components
4
July 2008
PacketCable VoIP Network Components
The PacketCable architecture is based on many components and
systems working together.
▪ Embedded Multimedia Terminal Adapter (E-MTA): Single device
containing a DOCSIS cable modem and a telephony device that
provides one or more line interfaces
▪ Cable Modem Termination System (CMTS): Provides connectivity
between DOCSIS network and PacketCable devices; also performs call
authorization enforcement, bandwidth allocation, and call trace functions
▪ Call Management Server (CMS): Provides call control and signaling
services for the MTA, CMTS, and PSTN gateways; typically performs
both Call Agent (handles call state) and media gateway controller
(authorization) functions as well.
5
July 2008
PacketCable VoIP Network Components
▪ SYSLOG server: Optional server used to collect,
store, and retrieve logging messages for devices
on the network
▪ DHCP Server: Provides initial boot-up networking
information such as the querying device’s IP
addresses, next-hop routers, server information,
etc.
▪ DNS Server: Provides translation between the
Domain name and the IP address of a device
▪ TFTP/HTTP server: Provides download capability
for device configuration files
6
July 2008
PacketCable VoIP Network Components
▪ Announcement Controller (ANC): Initiates and
manages all announcement services that are
provided by the announcement player
▪ Announcement Player (ANP): Delivers the
appropriate announcement(s) to the MTA under
control of the announcement controller
▪ Key Distribution Center (KDC): Performs security
key negotiations for MTA and Provisioning Server
in the PacketCable network
▪ Record Keeping Server (RKS): Collection point for
all PacketCable Event Messages; may also
correlate Event Messages to create Call Detail
Records for billing interfaces
July 2008
7
PacketCable VoIP Network Components
▪ Provisioning Server (OSS): Provides provisioning information for
PacketCable devices via SNMPv3
▪ Delivery Function (DF): Aggregation point for electronic surveillance;
delivers reasonably available call-identifying information and call content
based on the requirements of lawful authorization
▪ Media Gateway Controller (MGC): Provides bearer mediation between
the PSTN and the PacketCable network
▪ Media Gateway (MG): Provides media (voice packets) connectivity
between the PSTN and the PacketCable network
▪ Signaling Gateway (SG): Provides signaling mediation between the
PSTN and the PacketCable network
8
July 2008
E-MTA Installation
▪ The following should be standard installation practices:
- Pre Installation inspection:
•
•
•
•
•
Check for proper RF levels.
Check for damage or condition of splitters and couplers in Coax Drop
Check inside wiring for continuity at all jacks
Check for shorts or foreign voltages (AC or DC)
Check NID for proper wiring and ensure LEC connection is physically
disconnected
- Post Installation validation
• Check for dial tone at all jacks
• Make test calls on all customer premise equipment
• Educate customer on equipment and features
Comprehensive Methods & Procedures and Thorough Training of
Installation Personnel Are Key Factors for Success
9
July 2008
E-MTA Installation
▪ Customer Education
- Equipment
• Customers need to be educated to not unplug the EMTA or
connect to a switched outlet otherwise phone service can be
disrupted
• Customers need to understand that EMTA consumes very little
standby power - similar to a night light.
• Educate customer to not place EMTA where liquids may be spilled
into it
- Features
• Educate customer on how to use call features, provide reference
literature/handbook
• Educate customer that certain features require compatible CPE:
e.g. Call Waiting Deluxe, Caller ID, Message Waiting Indicator
10
July 2008
Troubleshooting
Causes of Voice Problems
▪ HFC plant condition
▪ Typical inside wiring faults
▪ No dial tone
▪ Too much delay on calls
▪ Voice breaking up
▪ The caller hears voice distortion
▪ Echo
▪ Static on the line
▪ Calls will not go through
▪ Voice in only one direction
11
July 2008
HFC Plant Condition
Downstream Signal Noise Ratio
▪
The SNR reported by the CM is a rough estimation of the signal to noise ratio
at the F-connector. It is based on Modulation Error Ratio (MER).
▪
PHY performance beyond DOCSIS requirements is implementation
dependent and some devices may be able to operate in presence of SNR
values which are significantly lower than DOCSIS requirements.
▪
Thus, we provide following thresholds as values for troubleshooting but some
devices may be able to be functional even in yellow or red SNR indications.
For 256QAM we can roughly define:
SNR>30 – green
29<SNR<30 – yellow
SNR<29 – red
For 64QAM we can roughly define:
SNR>23.5 – green
21.5<SNR<23.5 – yellow
SNR<21.5 – red
12
TM508 Installation and Troubleshooting
July 21, 2015
RF Receive Power Level
▪ RF Receive level should have enough margin to
allow for plant drift
▪ Range is -15dBmV to +15dBmV
▪ Recommended values:
GREEN : -13dBmV to +13dBmV
YELLOW: -14dBmV to -13dBmV or
+13dBmV to +14dBmV
RED
: < -14dBmV or >+14dBmV
13
TM508 Installation and Troubleshooting
July 21, 2015
Transmit Power Level
▪ Recommended values(dBmV):
Modulation
QPSK
QAM8
QAM16
QAM32
QAM64
GREEN
< 56
< 52
< 52
< 52
< 52
YELLOW
56<tx<57
52<tx<53
52<tx<53
52<tx<53
52<tx<53
RED
>57
>53
>53
>53
>53
14
TM508 Installation and Troubleshooting
July 21, 2015
Typical Inside Wiring Faults
15
July 2008
Typical Inside Wiring Faults
LEC Line
NID
Alarm Panel
Phone Jacks
Serial wiring
X
Line
CPE
Home run wiring
X
Line
CPE
Outbound call attempting
to contact the monitoring
station goes nowhere
WRONG!
16
July 2008
RJ31X Plug for Security Systems
• Used to connect security system control panel to home
telephone wiring.
• Ensures control panel can disconnect phone users and has
priority to “seize” the line to call the alarm monitoring
station.
17
July 2008
Wiring a Security System with RJ31X
Demarcation
EMTA
LEC Line
X
X
Phone Jacks
RJ31X
Jack
Modular
Plug
R1
T1
Phones
R
T
Telco
Line
Alarm
Control
Panel
18
July 2008
Wiring a Security System with RJ31X
EMTA
Demarcation
NID
LEC Line
X
X
Phone Jacks
RJ31X
Jack
Modular
Plug
R1
T1
Phones
R
T
Telco
Line
Alarm
Control
Panel
19
July 2008
EMTA RJ-14 Connection to Inside Wiring
Method 1: Using L1/L2 and L2 Jacks
Not used
Line 1 Jacks
EMTA
Main Line 1 Jack
L1/L2 Jack
Line 1
Circuit
Line 2
Circuit
L2 Jack
Main Line 2 Jack
Line 2 Jacks
Separate 2 conductor
cords to connect lines 1
and 2
Not used
20
July 2008
EMTA RJ-14 Connection to Inside Wiring
Method 2: Using L1/L2 Jack Only
Not used:
Isolated from Main
Jack and Line 2 Jacks
EMTA
Line 1 Jacks
Main Jack
L1/L2 Jack
Line 1
Circuit
Line 2
Circuit
L2 Jack
Line 2 Jacks
RJ14 Feature:
Not used:
Facilitates distribution of
2 lines with a single 4
conductor phone cord
Isolated from Main
Jack and Line 1 Jacks
21
July 2008
Typical Inside Wiring Faults
Not used:
Method 2: Using L1/L2 Jack Only
Not Isolated
from Main Jack
Line 1 Jacks
EMTA
Fault in wiring or
jack causes L1
to L2 short
circuit
Main Jack
L1/L2 Jack
Line 1
Circuit
Line 2
Circuit
L2 Jack
Line 2 Jacks
RJ14 Feature:
Not used:
Facilitates distribution of
2 lines with a single 4
conductor phone cord
Isolated from Main
Jack and Line 1 Jacks
22
July 2008
Dial Tone Issues - Potential Root Causes
▪
▪
▪
▪
▪
▪
▪
▪
▪
▪
EMTA Provisioning Unsuccessful
Line card or house wiring issue (Line Card Protection state)
DNS Server lookup issues (CMS or FQDN)
Call Signaling messaging protocol problems between EMTA
and CMS
Slow or delayed response from CMS
ARP Issues
DHCP Lease expiration / obtaining new IP address
Insufficient Bandwidth on CMTS / Lack of US Grants
Intermittent Packet loss and packet retransmits due to RF
impairment or RF noise
T4 timeout loss of RF connectivity
23
TM508 Installation and Troubleshooting
July 21, 2015
Troubleshooting Dial Tone Issues
▪ Provisioning
- Verify that the E-MTA or NIU is registered with the CMTS
- Verify that the CMTS has connectivity to the VoIP Switch
- Verify the VoIP Switch has connectivity to the E-MTA or
NIU via ping
- Verify that the E-MTA or NIU has the correct IP address
for its call agent
- Verify that the subscriber is entered in the VoIP Switch
database and is active
24
July 2008
Troubleshooting Dial Tone Issues
▪ DNS Look Up Failure
- If the CMS FQDN DNS queries are unsuccessful then the
MTA will not be able to send messages to the CMS
▪ ARP Problems
- If the MTA does not receive a response to an ARP at the
beginning of the call there is no mechanism in place to
retry
25
July 2008
Troubleshooting Call Delay
▪ Users notice delay when the end-to-end delay
exceeds 150ms. At this point, voice quality may be
acceptable, but the delay is not. When this situation
occurs, the processing capabilities of the E-MTA
and/or MG are overwhelmed and not processing
voice traffic efficiently
▪ Buffering reduces jitter in the network; however, it
also adds delay as the traffic is adjusted to a fixed
rate
26
July 2008
Troubleshooting Voice Breaking Up
▪ Congestion in the IP network causes packet loss
▪ As multiple packets are lost, the listener will hear
jumps in the speaker’s voice
▪ As more packets are lost the distortion becomes
worse and conversation is difficult
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July 2008
Troubleshooting Echo
▪ What is echo?
- In a voice telephone call, an echo occurs when you hear
your own voice repeated, somewhat attenuated and
delayed
- An echo is the audible leak-through of your own voice into
your own receive (return) path.
- The louder the echo, the more annoying it is.
- The longer the delay, the more annoying it is.
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July 2008
Troubleshooting Echo
▪ Where does echo originate?
1. A signal is leaking from the transmit into the receive path
• Leaking in analog circuits only.
▪ Cross-talk
− electrically
from one wire to another
− acoustically through the air from a loudspeaker to a microphone.
▪ Reflections in the hybrid part of the analogue side
− Telephone
set, house wiring, dect
• Voice traffic in the digital part of the network is highly unlikely to leak
2. The original signal and the leaked signal arrive at the
subscribers ear at different times due to difference in
delay between the travel path of the original and reflected
signal.
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July 2008
Troubleshooting Echo
▪ The “friends” of echo
- Delay
• 25 milliseconds (ms) or less delay is inaudible; PSTN calls typically have
less delay in the network, and therefore are unlikely to have echo issues
• VoIP networks typically have delays well above 25ms, so enough room for
the echo to become annoying
▪ Over 400ms delay for a phone call is annoying even without echo
- Amplification/Attenuation
• Echo should be 55dB below original speech to not be considered
“annoying”
• Amplification and attenuation occur at various places in an end-to-end call,
and will be different for calls to and from different networks (fixed, cell,
international, different providers etc)
30
July 2008
Troubleshooting Echo
▪ Avoiding echo
- Reflections are a result of impedance mismatches
• Line card templates set the impedances
• Phones should be “approved for the country in which they are used
- Speaker phones can easily cause acoustic echo
- DECT phones are suspect as well
- Remember : Echo at subscriber A is likely to originate at
the remote end of a call (subscriber B), therefore it may
not originate in “your” part of the network, even though
your subscriber is the one hearing the echo, not the
remote subscriber.
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July 2008
Troubleshooting Echo
▪ Echo in digital segments
- I really said the digital portion of the network does not cause echo… but..
“we resolved echo several times by applying changes in the
digital portion..”
- The digital portion of the network can add delay, are amplification which
makes Echo “visible”
- Removing this delay / amplification may remove the annoyance level of the
echo
• Delay changes due to:
▪ Additional network elements (e.g.router)
▪ Changes in jitter buffers, packetization rates
• Amplification changes due to
▪ Different gain/loss settings in gateways / switches / trunks
32
July 2008
Troubleshooting Voice Distortion
▪ Caused by tandem encoding
▪ With this encoding (also called dual encodings or
dual compressions), digital calls routed to a tandem
(toll) office are converted to analog form for
processing and then reconverted to digital form for
further transmission
▪ Converting and reconverting more than twice
damages the signal and causes voice distortion
33
July 2008
Troubleshooting Static
▪ May be caused by interference with a cordless
telephone (2.4 GHz)
▪ Latency
▪ Jitter caused by congestion in the network
34
July 2008
Troubleshooting calls that will not go
through
▪ Problems with the CMS - during busy times it cannot handle
another call setup.
▪ PSTN-bound calls may bombard the MG and/or MGC to the
point that they cannot handle any more calls.
▪ The SG may not be receiving proper messages from the
PSTN.
▪ The call may not be set up properly through the PSTN.
▪ Congestion in the network
▪ The signaling information may be dropped by the network.
35
July 2008
Troubleshooting One Way Speech Path
▪ Causes for one-way audio are usually IP routing or
HFC issues.
▪ Routing may not be enabled on the routers or there
may be a problem with default gateways configured
at end stations.
▪ Determining the direction of the one way speech
path is useful in order to isolate DS and US specific
issues.
36
July 2008
Troubleshooting EMTA Power Problems
▪ The E-MTA is plugged in, but the Power light is off.
▪ Check all power connections.
▪ Is the AC adapter plugged in firmly at both ends?
▪ If you plugged the AC adapter into a power strip,
make sure the strip is switched on.
▪ Avoid using an outlet controlled by a wall switch, if
possible.
▪ Finally, check the fuse or circuit breaker panel.
37
July 2008
Troubleshooting Internet Access Issues
▪ It may take up to 30 minutes to establish a
connection the first time you power up the E-MTA.
▪ Some E-MTA have Standby that isolate PC from
the Internet.
▪ Check the front panel lights:
- The Power and Online lights should be on.
- If the Online light is blinking, press the Standby button.
- The Link light should be either on or blinking.
- If the Power light blinks for more than 30 minutes, call
your cable company for assistance.
38
July 2008
Troubleshooting Internet Access Issues
(continued)
▪ Check your cable connections. Connectors should
be finger-tight.
▪ The coax cable should not be pinched, kinked, or
bent sharply.
▪ Any of these issues can cause a break or short in
the cable (you may have to replace the cable).
▪ If you have one or more splitters between the EMTA and CATV outlet, remove the splitters and
connect the E-MTA directly to the outlet.
39
July 2008
Troubleshooting Internet Access Issues
(Ethernet)
▪ If you are using a hub, is the hub turned on?
▪ Are you using the right type of Ethernet cable?
(Straight cable for direct connection to a PC, crossover cable for connection to a hub.)
▪ Press the Reset button on the back of the E-MTA.
40
July 2008
Troubleshooting Slow Internet Access
▪ If the Web site you are visiting is very popular, that
site may be having trouble servicing all the
requests. If other sites download quickly, wait for a
few minutes and try again.
▪ Usage during peak hours may also affect the
connection speed.
▪ If your E-MTA is connected to a LAN (Local Area
Network), either directly or through a firewall, other
communications on the LAN may slow down your
connection.
41
July 2008
Troubleshooting EMTA Alarms
▪
▪
▪
▪
Call Agent Loss of Communications
Severity: Major, service-affecting
Cause: One of the following conditions has occurred:
The MTA did not receive a response from the Call Server for an NCS
message. Re-establishing communications with the Call Server clears
this alarm.
▪ The E-MTA received a NACK in response to the RSIP message that it
sent on initial registration to the call agent, resulting in CallP functionality
entering a “permanent error” state. Clearing the condition that caused
the NACK clears this alarm.
▪ Impact: The NIU cannot register or initiate calls.
▪ Action: Check the status of the NIU and its network connection.
42
July 2008
Troubleshooting EMTA Alarms
Power Supply Telemetry
Severity: Major, service-affecting
Cause: The NIU has lost AC power. The alarm includes one of the
following battery status codes:
▪ AC Fail—the NIU has detected an AC power failure.
▪ AC Fail Battery Low—the NIU is operating from battery power, and has
drawn down the battery to about 25 percent of its rated capacity.
▪ AC Fail Battery Replace—the NIU is operating from battery power, and
the battery has deteriorated to about 75 percent of its off-the-shelf
capacity and should be replaced.
▪ AC Fail Battery Low Replace—the NIU is operating from battery power,
and has drawn down the battery to about 25 percent of its rated
capacity. In addition, the battery has deteriorated to about 75 percent of
its off-the-shelf capacity and should be replaced.
43
July 2008
Troubleshooting EMTA Alarms
Power Supply Telemetry (continued)
▪ Impact: None at time of alarm. Depending on the
condition of the battery and the nature of the power
failure, the NIU may exhaust the battery before AC
power is restored.
▪ Action: Depends on the scope of the power
outage.
44
July 2008
Troubleshooting EMTA Alarms
Voice Line Failure
Severity: Major, service-affecting
Cause: One of the following conditions has occurred:
▪ An In-Service line card has detected a Line Card Protection
Fault condition (an overcurrent protection state). A Line
Card Protection Fault occurs when the line card detects
foreign voltage between tip and ring, or there is an
excessive imbalance in loop current.
▪ An attempt was made to put an Out-of-Service line, in an
overcurrent protection state, into service.
45
July 2008
Troubleshooting EMTA Alarms
Voice Line Failure (continued)
▪ Impact: The affected voice line is disabled. Look
for Voice Line Protection State Change logs to
determine which line is in the fault condition.
▪ Action: Run the line card diagnostics on the NIU. If
the NIU fails diagnostics, disconnect the house
wiring from the NIU and proceed as follows:
▪ If the alarm clears, correct the faulty house wiring.
▪ If the alarm persists, replace the NIU.
46
July 2008
E-MTA Registration - Common Problems
Power - Telephony modem is not receiving AC
power.
▪ Verify power cord is plugged into an unswitched
outlet.
▪ Verify power cord by measuring with voltmeter.
Voltage should be 100-240V 50-60Hz.
▪ If unit is receiving power from outlet and power
cord, replace with another unit.
47
July 2008
E-MTA Registration - Common Problems
▪ Downstream Scanning - Telephony modem is not able to lock onto a
downstream signal.
▪ Verify cabling from house splitter to unit.
▪ Verify Downstream signal level at assigned frequency is within the
telephony modem Rx range -15dBmV to +15dBmV.
▪ If no signal, verify the drop by measuring a CATV channel level for
proper level at the CPE demarcation point.
▪ If CATV channel is at the proper level, contact head end to verify CMTS
is transmitting.
▪ If CATV channel is not present, troubleshoot drop cable from the tap.
▪ If Downstream signal is at proper level, replace unit.
48
July 2008
E-MTA Registration - Common Problems
Upstream Ranging – E-MTA is not able to
establish upstream communications with the
CMTS.
▪ Verify cabling from house splitter to unit.
▪ Verify upstream path by sending signal back to
head end and measure for proper level.
▪ Contact head end to verify CMTS RF level is set to
proper level.
▪ If Upstream signal loss is at proper level, replace
unit.
49
July 2008
E-MTA Registration - Common Problems
DHCP – E-MTA is not receiving a IP address for
the data component from the DHCP server.
▪ Contact head end to verify DHCP server is
functional and receiving address requests from
unit.
▪ Head end should verify provisioning information.
50
July 2008
E-MTA Registration - Common Problems
TFTP – E-MTA is not able to download the
configuration file for the data component from the
TFTP server.
▪ Contact head end to verify TFTP server is
functional and receiving configuration file requests
from unit.
▪ Head end should verify provisioning information.
51
July 2008
E-MTA Registration - Common Problems
▪ Telephony DHCP – E-MTA is not receiving an IP
address for the MTA component from the
Telephony DHCP server.
▪ Contact head end to verify Telephony DHCP server
is functional and receiving address requests from
unit
▪ Head end should verify provisioning information.
52
July 2008
E-MTA Registration - Common Problems
Telephony TFTP – E-MTA is not able to download
the configuration file for the MTA component from
the Telephony TFTP server.
▪ Contact head end to verify Telephony TFTP server
is functional and receiving configuration file
requests from unit.
▪ Head end should verify provisioning information.
53
July 2008