Benefits of ISDN Trunk Group Load Balancing
In this post “Benefits of ISDN Trunk Group Load Balancing” you get to identify trunk capacity, and ISDN trunk group load balancing techniques for inbound and outbound call handling, as well as best practices.
Not so long ago I was at customer site trying to identify why outgoing calls were not working on peak hours. This Avaya IP Office had a total of three ISDN-PRIs use for inbound and outbound calls, with 168 End-points.
When I arrived to the site, and met with the site contact, they seemed very frustrated with the phone system. Trying to be proactive the customer had the Voice Carrier troubleshooting the problem, and they were pointing the problem to the Avaya System (IP500v2). Besides dropped outgoing calls they were experiencing QoS issues such as Jitter and Latency on their calls.
To help troubleshooting this issue, I developed these procedures=
- 1.- Data gathering
- 2.- Workflow Template
- 3.- Exercise the plan
- A.- Solution
- B. Resources
1.- Data gathering
- Analyze – It is good to analyze the problem before developing a plan, hence for better end-results.
- Contact the Service Provider– Before I started working on solving this problem, I had the customer contact their Voice Carrier. I then asked them, how many concurrent calls were they allowing, and what type of codec was implemented.
The customer had these circuits working prior to this new Voice Provider came to the picture. With the new setup the new Voice Carrier is allowing a maximum of 40 concurrent calls using codec type of G.711.
2.- Workflow Template
By now I had all my notes taken. My next step was creating a step by step workflow and sharing it with the client. This Workflow template shouldn’t be more than five steps. For this customer I had included two steps=
Site Survey – This is a quick survey of their voice equipment setup. Identify the trunk circuit IDs, connections, and devices. I learned that they had two IAD Routers connected to three T1s provided by the LEC. These circuits were coming into the IAD as SIP Data traffic, then converted to ISDN-PRI T1s in order to work with the PBX (Avaya IP Office).
Inventory – The only thing to inventory here is the trunks, and licenses. Use System Status to check the resources available, as well as licenses, and trunk usage.
3.- Exercise the plan
With the notes taken from the conference call, site survey, and inventory, it is time to get to work.
“Load Balancing ISDN Trunk Groups” a quick overview – When working with multiple trunk groups, it is always important to load balance your incoming and outgoing traffic.
Load-balance the incoming traffic – Have the Voice Carrier configure their traffic as ascending (starting at channel 1 thru 23), with trunk group overflow, which will allow calls to hunt from one trunk group to the second trunk group, whenever it reaches its full capacity.
Load-balance the outgoing traffic – In the Avaya PBX, configure the Trunk Group as descending. Assign different Trunk Group IDs to each T1 to allow you designate which trunk group should be use for outbound traffic.
By applying this load-balancing rule, the system will utilize each designated trunk channel; improving the system performance. In my case this customer had two trunks groups used at full capacity, and the third trunk almost never.
These T1s were designed to be part of one trunk group “0”. for incoming and outgoing traffic. which is not the best solution for troubleshooting. Having two DS1s configured as Primary Sync Sources from the Voice Carrier, the third T1 was configured as “unsuitable”.
A.- Solution
To fix the Syncing and Trunk Assignment Issues. First segregate the T1s by assigning unique trunk groups to each one of them, then choose the main DS1 sync source, and set it as the “primary”, the second DS1 should be set as “Fallback”, and finally the third one should be set as “Unsuitable”.
Because the old configuration was set to allow 69 concurrent calls over PRIs, and the new solution for 40 calls, this issue will only be fixed by adding more bandwidth to their existing data. Or by implementing G.729a as the codec type. In the meantime the only thing left it’s un-assigning 29 b-channels off the trunk groups, leaving us with a full T1, and only 6 b-channels in the second T1.
B.- Resources
Avaya IP Office Monitor – this tool is useful to log system events to a file. The filter options allows for customizing different types of traces. To download the Avaya Manager and its components follow this link= https://support.avaya.com/downloads/download-details.action%3FcontentId%3DC201391714203650_5%26productId%3DP0160
Avaya IP Office System Status – This a java application offering a GUI interface with the ability of login realtime system events, alarms, troubleshooting tools, and much more. It allows to take a snapshot of the system activities as well as “continues logging” .
Please note: I reserve the right to delete comments that are offensive or off-topic.