What are Inbound SIP Trunk Calls? Will it Fit your Business?

SIP trunking is an alternative to purchasing hosted VoIP services from a vendor. A business can purchase an IP PBX, connect it to SIP trunks from a vendor and start making calls. You may even be able to use your existing equipment with a VoIP gateway in this setup. Even though it requires a bit more effort and costs more initially than hosted services, it’s less expensive over the lifetime of the equipment.

What Is an SIP Trunk?

Conceptually speaking, SIP trunks are very similar to the enterprise trunks you could buy from phone carriers for service. A “Trunk” refers to a bundle of individual, physical phone lines that connected a business to the operator. Analog trunks have 23 voice channels, allowing clients to handle 23 concurrent calls. If you need more, you had to purchase additional trunks each of which comes with its own 23 voice channels.

Practically speaking, SIP trunks are very different. For one thing, an SIP trunk is not actually a physical line. There are no copper wires between your office and the vendor. SIP trunks refer to digital lines – where your system connects to the SIP vendor through a data connection. They are called trunks because of the conceptual similarity to their older counterparts.

SIP trunks are more flexible as well. You don’t have to purchase trunks in terms of 23 channels or 46 channels. Simply purchase as much capacity as you need, when you need it. You don’t have to wait until the end of the month or until your contract expires either. Most reputable vendors allow you to adjust lines – adding or deleting them – on the fly.

Provisioning SIP Trunks

SIP trunks are designed to be flexible. So how do you answer the question of how many trunks do you need? Generally, you define the capacity of a trunk based on the number of simultaneous calls and bandwidth requirements for each call.

SIP trunking providers usually offer pricing plans based on capacity. You can start off at the closest tier to your estimated capacity and scale up or down from there. The beauty of SIP trunking is that it can scale almost instantly. There is no waiting while a technician comes out to your office and physically connects a new trunk. Most vendors will be able to provision extra capacity in a few hours at most.

A few providers even have the option of provisioning new instances automatically or auto scaling. That means if it looks like calls are getting close to the trunk capacity, they will provision extra lines without manual intervention. You can reduce capacity when call volume goes down. That way, you only pay for the resources you used and not a penny more.

Inbound SIP Trunk Calls

Within the phone system, there are many types of calls. One distinction is between internal and external calls. For example, suppose one employee in your office calls a colleague on another floor. This call doesn’t leave your company network at all. Such calls are internal calls and do not touch the public networks at any time. On the flipside, external calls are those that cross the boundaries of your organization. Calls from your salespeople to potential customers, clients calling tech support etc. are all external calls.

Another distinction is the direction of calling. When someone within your company initiates a call, it is an outbound call. On the other hand, if a customer or supplier calls your business, it’s called inbound calling. Some features like call routing, multi device ring etc. are specifically designed to help manage inbound calls.

Inbound Call Routing

When a call comes in on your SIP trunk, you have to decide what to do with it. Is it a direct number for an employee or department? Should it ring multiple devices or go to a queue? Should you setup an auto attendant to handle all calls?

These kinds of decisions are related to inbound call routing. As a business, you can set up various rules depending on the number being called, the type of calls or even time of day. Suppose your office hours are from Monday to Friday, 9 AM to 9 PM. You can configure the system to direct callers to the IVR (Interactive Voice Response) or even send calls to a location in another time zone that is still open.

Individual users can also set their own configuration for managing incoming calls. For instance, an executive may allow calls from managers to his office. Calls from salespeople are automatically directed to his personal assistant. Others are sent to voicemail when the executive is busy.

SIP trunks are cost-effective over the long-term. For organizations that experience high call volume, SIP trunks offer lower costs per call than the equivalent hosted VoIP service. If you need control over your phone system and have the in house expertise, SIP trunking is the way to go!