SL-1 / Meridian Traffic Study Explanation

This page describes the contents of a standard traffic study for Northern Telecom’s SL-1/Meridian 1 PBX. Each section refers to an individual traffic report and includes a description of each column in the report.

Reporting Standards

Intracustomer Network Traffic

Trunk Routes

Tandem Network Traffic

Current vs. Optimal Trunks

Processor Utilization

Trunk Route Traffic

Service Traffic

Console Group Traffic

Junctor Traffic

Console Member Traffic

Line Report Information

Dial Tone Delay Traffic

Netwk Class of Svc Measurem't

Feature Traffic

Route List Measurements

Network Loops

Route List Entry Counts

Network Loop Traffic Utilization

D Channel Information

Incoming Network Traffic

MISP D Channel Management

Outgoing Network Traffic

About Traffic Studies



Reporting Standards


For Daily reports, the Date column indicates the date the traffic occurred and the Busy Hour column indicates the hour during that day when the most traffic occurred. All traffic statistics in that row provide the traffic for only the Busy Hour listed.
For Peak reports, the Peak Date and Peak Hour columns indicate the day and hour when the most traffic occurred during the period of the traffic study. All traffic statistics in that row provide the traffic for only the Peak Hour listed.
For Hourly reports, the Date column indicates the date the traffic occurred and the Hour column indicates the hour the traffic occurred. The Busy Hour column indicates the hour during that day when the most traffic occurred.
The dates on the top of the first page of each report indicate the dates included in the traffic study. The Run Date & Time at the bottom of the report indicate when the report was produced.
Unless otherwise noted on a report, all traffic usage is expressed in hours and minutes. For example, 2:54 indicates two hours and 54 minutes. The hours and minutes were derived from the switch data that measures traffic in centum call seconds (CCS). One CCS equals 100 seconds.
A blank cell on a report indicates that there is not data for this cell. Either the switch did not provide any data for this measurement, or there is no data because the calculation attempted to divide by zero.
Peg counts (or simply "pegs") measure events or occurrences. For example, if ten calls were made in an hour, the peg count would be ten. With each additional call, the peg count is increased by one. Peg counts are also used to measure the number of times a feature or service was used, an All Loops Busy occurred, or other events occurred.




Trunk Routes


Trunk Route Indicates the identifying trunk route number
Type Indicates the type of service the trunk provides
Description Provides the customer description of the trunk route
Size Equals the number of trunks configured in the route


Engineering Model Indicates the engineering table used to define the grade of service
Erlang B Erlang B is a probability distribution that assumes that a call, failing to find an idle trunk, immediately drops and the source becomes idle. Lost calls are cleared. Generally, Erlang B is used for today’s digital PBX’s.
Erlang C Erlang C is a probability distribution that assumes that all callers will wait indefinitely to get through. Generally, Erlang C is used when is queuing in place.
Poisson Poisson is a probability distribution that assumes that a call, failing to find an idle trunk, is held for a holding time before the system drops the call. This table usually designates more trunks needed to compensate for the holding time than the Erlang B table. Usually used if switch was originally engineered using Poisson or requested.


Grade of Service Indicates the Grade of Service. Grade of service measures the percent of calls blocked on a trunk route. It is the primary measurement that traffic engineers use to indicate the service that a trunk route provides. For example, a grade of service of 0.01 allows 1% of all calls to be blocked.




Current vs. Optimal Trunks Graph


Grade of Service Indicates the Grade of Service. Grade of service measures the percent of calls blocked on a trunk route. It is the primary measurement that traffic engineers use to indicate the service that a trunk route provides. For example, a grade of service of 0.01 allows 1% of all calls to be blocked.
Trunk Members Indicates the current and optimal number of trunks in the route
Current Equals the current number of trunks configured in the route
[ < ] Optimal Equals the numbers of trunks that do not provide the target grade of service for the current traffic
Optimal Equals the optimal number of trunks for the target grade of service for the current level of traffic
[ > ] Optimal Equals the numbers of trunks that provide a grade of service that is higher than the target, for the level of current traffic
Total Traffic During Peak Hour of Study Equals the hours and minutes of traffic on this trunk route during the highest busy hour during the traffic study period
Engineering Model Equals the engineering table used to define the grade of service: Erlang B, Erlang C, or Poisson
Target Grade of Service Equals the grade of service required for this switch
Actual Grade of Service Equals the actual grade of service for the current number of trunks




Trunk Route Traffic


Trunk Route Indicates the identifying trunk route number
Type Indicates the type of service the trunk provides
In USG Equals the incoming traffic measured in hours and minutes
Out USG Equals the outgoing traffic measured in hours and minutes
In Peg Equals the number of incoming calls that occurred within the hour
Out Peg Equals the number of outgoing calls that occurred within the hour
OVFL Equals the number of calls that failed for a trunk in this route because there was not an idle and enabled trunk available
ATB Equals the number of times the last enabled trunk is busy (only valid for trunk routes with at least one equipped member)
% Calls Blocked Equals the estimated percentage of total calls lost from blocking or overflow, for this particular route; % Calls Blocked = (OVFL * 100) / (OVFL + Out Peg)
Total USG Equals the total traffic measured in hours and minutes; Total USG = In USG + Out USG
Avg USG Equals the average usage per working trunk; Avg USG = Total USG/TRK WKG
Total Peg Equals the total number of calls that occurred within the hour; Total Peg = In Peg + Out Peg + Overflow Peg.
Avg Peg Equals the average number of calls per working trunk; Avg Peg = Total Peg/TRK WKG
TRK QTY Equals the number of trunks configured in the route during this hour
TRK WKG Equals the number of trunks working or enabled in the route during this hour




Console Group Traffic


Staffed Time Equals the time that attendants spent on calls and waited to receive calls; this statistic is accrued only when the attendant is in "day" mode
Total Offered Calls Equals the total number of internal and external calls that would have been answered had none been abandoned
Total Answered Calls Equals the total number of internal and external calls answered
Abandoned Call Rate Abandoned Call Rate = Total Abandoned Calls / Total Offered Calls
Avg Wait Before Abandon Equals the average number of seconds callers waited before abandoning (hanging up) the call
Avg Speed of Answer Equals the average number of seconds before a call is answered once its request to terminate at an Attendant is recognized. This includes incoming, dial 0, and recalls
Time in Queue Equals the average number of seconds that calls waited in a queue
Avg Internal Call Equals the average number of seconds spent talking per call that originated inside the system
Avg External Call Equals the average number of seconds spent talking per call that originated outside the system
Avg Call Equals the average number of seconds spent talking per internal and external call
All Loops Busy Equals the number of times during the hour that all loops were busy




Console Member Traffic


ID Indicates the attendant’s identification number
Staffed Time Equals the time that the attendant was in Day Mode during the hour
% of Time Idle Equals the percent of time the attendant is in Day Mode but is not servicing calls
Internal Answered Calls Equals the number of completed calls that originated from within the PBX
Internal Average Talk Time Equals the average length of internal calls serviced by the attendant
Internal Carried Traffic Equals the total time the attendant serviced internal calls
External Answered Calls Equals the number of completed calls that originated from outside the PBX
External Average Talk Time Equals the average length of external calls serviced by the attendant
External Carried Traffic Equals the total time the attendant serviced external calls
Total Answered Calls Equals the number of completed internal and external calls
Total Average Talk Time Equals the average length of internal and external calls serviced by the attendant
Total Carried Traffic Equals the total time the attendant serviced internal and external traffic
All Loops Busy Equals the number of times when the last Loop Key on the attendant is made busy




Dial Tone DelayTraffic


Calls Delayed Over 3 Seconds Equals the number of calls that experienced a dial tone delay greater than 3 seconds
Calls Delayed Over 10 Seconds Equals the number of calls that experienced a dial tone delay greater than 10 seconds. Note that a call that is delayed for greater than 10 seconds will increment both this count and the Delay Over 3 Seconds count.
Total Delay of All Delayed Calls Equals the total delay suffered for all requests that were delayed for at least one second




Feature Traffic


Feature ID Indicates the identification number of the feature type
Feature Description Provides the customer description of the feature type
Times Used Equals the number of times the feature was used




Network Loops


Loop Number Indicates the unique loop number in the network
Loop Type Indicates the type of network loop
Description Provides the customer description of the network loop




Network Loop Traffic Utilization


Loop No. Indicates the unique loop number in the network
Loop Type Indicates the type of network loop
Traffic Equals the amount of time slot usage handled for inter-loop and intra-loop traffic. Note that intra-loop calls accumulate usage for both network loops.
Intra Failures to Match Equals the number of times when a path cannot be found between two terminals on the same loop
Loop Failures to Match Increments for the total loop when a connection between two terminals cannot be made.
% Utilization % Utilization = (Total Carried Traffic / Capacity of Network Loop) * 100
Over Utilized A check mark will appear if the loop is over utilized, when in accordance to Nortel’s standard of traffic levels for a superloop, terminal, conference, or TDS loop.




Incoming Network Traffic


Incoming Traffic FTM Equals the number of incoming calls that experienced blockage because the trunk was not available.
Incoming Traffic Peg Equals the number of incoming calls from the network
Incoming Traffic USG Equals the network incoming traffic measured in hours and minutes
Incoming % of Total USG Equals incoming usage divided by total usage
Total Traffic FTM Equals the total incoming, outgoing, tandem, and intra-customer calls that experienced blockage because the trunk was not available or, if intra, no path between two terminals available.
Total Traffic Peg Equals the total incoming, outgoing, tandem, and intra-customer calls
Total Traffic USG Equals the total incoming, outgoing, tandem, and intra-customer traffic measured in hours and minutes




Outgoing Network Traffic


Outgoing Traffic FTM Equals the number of outgoing calls that experienced blockage because the trunk was not available.
Outgoing Traffic Peg Equals the number of calls outgoing to the network
Outgoing Traffic USG Equals the network outgoing traffic measured in hours and minutes
Outgoing % of Total USG Equals outgoing usage divided by total usage
Total Traffic FTM Equals the total incoming, outgoing, tandem, and intra-customer calls that experienced blockage because the trunk was not available or, if intra, no path between two terminals was available .
Total Traffic Peg Equals the total incoming, outgoing, tandem, and intra-customer calls
Total Traffic USG Equals the total incoming, outgoing, tandem, and intra-customer traffic measured in hours and minutes




Intra-customer Network Traffic


Intra-customer Traffic FTM Equals the number of intra-customer (station to station) calls that experienced blockage because a path between two terminal, (neither one a trunk) was available.
Intra-customer Traffic Peg Equals the number of intra-customer calls
Intra-customer Traffic USG Equals the intra-customer tandem traffic measured in hours and minutes
Intra-customer % of Total USG Equals intra-customer usage divided by total usage
Total Traffic FTM Equals the total incoming, outgoing, tandem, and intra-customer calls that experienced blockage because the trunk was not available or, if intra, no path between two terminals available.
Total Traffic Peg Equals the total incoming, outgoing, tandem, and intra-customer calls
Total Traffic USG Equals the total incoming, outgoing, tandem, and intra-customer traffic measured in hours and minutes




Tandem Network Traffic


Tandem Traffic FTM Equals the number of tandem (trunk to trunk) calls that experienced blockage because a path between two trunks could not be found
Tandem Traffic Peg Equals the number of tandem calls in the network
Tandem Traffic USG Equals the network tandem traffic measured in hours and minutes
Tandem % of Total USG Equals tandem usage divided by total usage
Total Traffic FTM Equals the total incoming, outgoing, tandem, and intra-customer calls that experienced blockage because the trunk was not available or, if intra, no path between two terminals available.
Total Traffic Peg Equals the total incoming, outgoing, tandem, and intra-customer calls
Total Traffic USG Equals the total incoming, outgoing, tandem, and intra-customer traffic measured in hours and minutes




Processor Utilization


CPU Utilization Left CPU Utilization Left = 100 - CPU Utilization Used
CPU Utilization Used Equals the percent of CPU capacity used, calculated by comparing the highest idle cycle count daily to the lowest cycle count of the study




Service Traffic


Service No. Indicates the identification number of the service type
Service Description Provides the customer description of the service type
Requested Equals the number of calls that attempted to use the service type
FTM Equals the number of calls that experienced failed attempts to use the service type
Carried Equals the number of calls that used the service type
Traffic Carried Equals the amount of time spent using the feature, including any call setup time




Junctor Traffic


FTM Equals the number of times a junctor failed to match while attempting to set up a connection between network groups
Usage Equals the amount of time that the time slots of the junctor group were busy
Peg Count Equals the number of completed calls between network groups




Line Report Information


Peg Count Equals the number of calls established for terminals within a loop.  If two terminals within the same loop establish a call, two calls will be pegged.
Time Equals the amount of time for all calls in a loop
Average Holding Time Indicates the average amount of time a call is in progress




Network Class of Service Measurements


Network Class Identifies the switch defined network class of service
Attempted Calls Equals the total number of network call attempts by users assigned to a specific network class of service
Requests Not Delayed Equals the number of calls routed without encountering blockage
Expensive Route Acceptances Equals the number of calls that are allowed to complete over an expensive route
Requests Blocked Equals the number of calls in a network class that could not be served because a route was not available
Expensive Routes Refused Equals the number of calls that received an Expensive Route Warning Tone




Route List Measurements


Route List Requests Equals the number of times the system selects a specific route list
Requests Note Delayed Equals the number of calls that did not encounter blockage or queuing
Expensive Route Acceptances Equals the number of calls routed by choice over an expensive route after receiving the Expensive Route Warning Tone
Requests Blocked Equals the number of calls that could not access a route or queue




Route List Entry Counts


Entry List Numbers 0 through 9 Equals the number of calls successfully routed over each of the first ten route list table entries




D Channel Information


D Channel Indicates the specific D channel
In Msgs Equals the number of incoming messages received on the D channel
Out Msgs Equals the number of outgoing messages sent on the D channel
In Proc Msgs Equals the number of incoming call processing messages received on the D channel
Out Proc Msgs Equals the number of outgoing call processing messages sent on the D channel
Avg Out Bytes Per Msg Equals the number of outgoing bytes per message
Connected Calls Equals the number of connected calls
Time in Sec Last Cleared Equals the time (in seconds) since the D channel traffic was last cleared
% Peak In Link Use 5 Secs Equals peak incoming link usage shown as a percentage of the link capacity over a five second period
% Peak Out Link Use 5 Secs Equals peak outgoing usage shown as a percentage of the link capacity over a five second period




MISP D Channel Management


MISP Indicates the Multi-purpose ISDN Signaling Processor (MISP) number
Calls Attempted Equals the number of attempted calls both complete and incomplete
Successful Calls Equals the number of successfully completed calls
Avg  Call Duration Equals the average length of a successfully completed call (in seconds)
MISP/BRSC Sig. Msgs Equals the number of signaling messages sent by the MISP, the BRSC, or both to the terminals on the D channels
Terminal Sig Msgs Equals the number of signaling messages sent by the terminals to the MISP, BRSC, or both on the D channels
MISP or BRSC Data Packets Equals the number of D channel data packets sent by the MISP, BRSC, or both to the terminals
Terminal Data Packets Equals the number of D channel packets sent by the terminals to the MISP, BRSC, or both