CDR Analysis Report tool

CAR Report

Stands for Call Detail Record Analysis and Reporting -> CDR A R -> CAR report tool

Functions

General parameters, system settings, schedule options and database

Basically, every call that CUCM processes can be logged, called Call Detail Records(CDR) and CMRs which contains information about the call and voice quality metrics for the call. These CDRs are stored as a flat file on the subscriber server and uploaded to the CAR/CDR database on the publisher server.

How to activate

Cisco Serviceability > Tools > Service Activation > Select the Cisco CAR Web Service and click Save

Jitter

Jitter is defined as a variation in the delay of received packets. That is, Jitter = Delay Variation

Due to network congestion, improper queuing or configuration errors, this steady stream can become lumpy, or the delay between each packet can vary instead of remaining constant

Determine the severity of Jitter

Once a call is up and active, jitter is suspected, telnet or ssh to one of the gateways involved

Enter show voice call summary

Selected the port where the jitter is experienced

Enter show voice call [port]

View the ***DSP VOICE VP_ERROR STATISTICS*** section in the output

What causes Jitter?

Jitter is generally caused by congestion in the IP network. The congestion can occur either at the router interfaces or in a provider or carrier network if the circuit has not been provisioned correctly.

Reference

https://www.cisco.com/c/en/us/support/docs/voice/voice-quality/18902-jitter-packet-voice.html#topic1

show isdn q921

The show isdn status command displays the status of all ISDN interfaces or a specific ISDN interface.

When troubleshooting ISDN Basic Rate Interface (BRI), it is necessary to first determine if the router can properly communicate with the Telco ISDN switch.

Once this has been verified, you can proceed on to higher level troubleshooting issues.

Layer 1 status – physical layer connectivity
Layer 2 status – Terminal Endpoint Identifier (TEI) Number and mulitiframe structure

The valid TEI number range = 64 to 126

The most often seen Layer 2 states are;
- MULTIPLE_FRAME_ESTABLISHED
This indicates that the state is under normal operations.
- TEI_ASSIGNED
This indicates that the router has lost connectivity to the switch. It is not the usual case unless the Telco (commonly in EU) deactivates Layer 1 and 2 when there are no active calls.

Troubleshoot commands
Debug isdn q921 or q931(If the Layer 3 issues)
Clear interface bri

Service Profile Identifiers (SPID) status
· state = 1(terminal down)
· state = 3(await establishment)
· state = 5(init)
· state = 6(not initialized) 

· state = 8(established)

Distance Vector VS Link State

Routing table can be managed by 2 different methods

Distance Vector

·       RIP, IGRP

·       It doesn’t have all routing information which saves memory and structure of table is very straight-forward

·       Even if no changes in the routing table, it automatically updating the routing table which causes increase in traffic and high CPU usage in the router.

·       Convergence time is longer than Link State

·       Best for small business

Link State

·       OSPF

·       One Router of the network has all routing information

·       Find the best route based on the Shortest Path First algorithm

·       Information sharing takes place only whenever there is a change

·       Best for medium or higher business

Problem of Distance Vector

·       One specific router has all routing information

·       Looping

·       Long convergence time

Solutions for Looping

·       Maximum Hop Count is 15

·       Hold Down Timer

·       Split Horizon – A router will not advertise a route back onto the interface from which it was learned. Split horizon is enabled on interfaces by default.

·       Route Poisoning – When a router detects that one of its directly connected routes has failed, it will advertise a failed route with an infinite metric (“poisoning the route”). Routers who receive the routing update will consider the route as failed and remove it from their routing tables.

·       Poison Reverse

ACL

Standard Access List

1-99, 1300-1999

Only controls the source address

Router(config)#access-list access-list-number {permit | deny} {source-wildcard | any}

Router(config)#ip access group access-list number {in | out}

Extended Access List

100-199, 2000-2699

Source address, destination address, protocol and port number

Router(config)#access-list access-list-number {permit | deny} protocol source source-wildcard [operator port] destination destination-wildcard [operator] [established] [log]

Router(config)#ip access-group access-list number {in | out}

Voice Activity Detection (VAD)

Most IP-based Telephony systems include a voice activity detector.

The purpose of the detector is to detect silence periods in the voice signal and temporarily discontinue transmission of the signal during the silence period. This saves bandwidth and allows the far-end to adjust its jitter-buffer.

Tune VAD Parameters

• music-threshold (Default value is -38dBm)
• voice vad-time (Default value is 250 msec)

Turn VAD off

• no vad command under the VoIP dial-peers

Understanding in QoS

For a VoIP network to operate successfully, the voice traffic must have priority ove the data traffic as it traverses its way form one end of the network to the other.

There are many enemies of your VoIP traffic

• Lack of bandwidth
• Delay - Jitter
• Packet Loss

QoS is designed to keep voice traffic running smoothly during temporary moments of congestion
on the network.

Bandwidth requirements

• End-to-end delay = 150ms or less
• Jitter = 30ms or less
• Packet Loss = 1% or less

QoS mechanisms

• Best effort - This is the model every network uses by default. All traffic is treated on  FIFO basis.
• Integrated Services (IntServ) - It it only model that provides 'Guaranteed' bandwidth but it has scalability issues becauses each router must track every single traffic flow. If enough reservations are made, the network simply runs out of bandwidth
• Differentiated Services (DiffServ) - Most popular and flexible model to use for impletmenting QoS. It provides that a Per-Hop-Behavior, Traffic conditioning and SLA

References
http://middleware.tistory.com/entry/IntServ-%EB%B0%8F-DiffServ
Cisco Official Cert Guide