How a SIP Registrar Simplifies Remote Work

Disclosure: Our content is reader-supported, which means we earn commissions from links on Crazy Egg. Commissions do not affect our editorial evaluations or opinions.

Every day, new tools and systems are being developed to make remote work easier. In some cases, however, the technology we use to facilitate these remote working environments has already been around for years. This is the case with SIP registrar technology.

A SIP (Session Initiation Protocol) registrar is a key component that enables real-time communications like Voice over Internet Protocol (VoIP) and video conferencing to work seamlessly for remote workers. It acts as a directory that maps usernames or Addresses of Record (AORs) to a user’s current location.

For example, if a client or customer tries to call a remote worker while they are out of the office, the SIP registrar knows the IP address of the worker’s laptop or mobile device. This allows the call to connect even if the remote employee is moving between different networks.

Without a registrar, real-time communications would break every time someone switched networks. This is a huge consequence for remote workers, considering how often they might change between working from corporate offices, co-working spaces, coffee shops, hotels, or even their own homes.

Technically, What is a SIP Registrar?

A SIP registrar is a server that receives and processes SIP REGISTER requests and is designed to optimize your VoIP network. These SIP REGISTER requests allow SIP user agents to register their current location on a dynamic basis so that incoming calls can reach them.

For reference, a SIP user agent can be any endpoint device like an IP phone, softphone, mobile app, or communications server that interacts with other SIP components using the Session Initiation Protocol to make or receive calls.

Once the SIP REGISTER request has been processed, the registered SIP address becomes an Address of Record (AOR). An AOR is a SIP identifier that looks something like sip:username@domain. Here, the username is always a unique name, and the domain is typically the VoIP domain of the business.

After the address has been registered and a new user agent starts up, it sends a SIP REGISTER message to its configured registrar server. This associates the AOR with the contact’s uniform resource identifier (URI), which contains the device’s current IP address or wherever the user can be reached at the time.

As a result, SIP registrars are able to provide a lookup service by mapping AORs to contact URIs. They also remove mappings when the registration expires, which is dictated by the Expires header in REGISTER messages. This ensures communications are routed to the user’s current location.

Note: If all of this is sounding a little too technical, another way of looking at SIP registrar technology is to think of it like a concierge desk at a hotel; while the registrar is the concierge, the SIP user agents are the hotel guests checking in.

Furthermore, each hotel guest has a room number that identifies them, just like a SIP Address of Record (AOR). When guests check into the hotel, they tell the concierge their name and room number (assuming they knew it beforehand). This is like a SIP user agent sending a REGISTER message that includes its AOR.

The concierge then records each guest’s name and current room phone number in a book. This registration binds their identity to a given phone contact, much like a SIP registrar mapping AORs to contact URIs.

Later, when someone calls the hotel asking for a guest, the concierge looks up the room number to find the guest’s current room phone to connect the call (assuming they may have changed rooms for whatever reason). This is similar to a SIP proxy querying the registrar to route calls to the user agent’s latest contact regardless of whatever network they’ve switched to.

Finally, when the guests check out, the concierge removes their occupancies just as expired registrations get removed.

SIP Registrar vs. SIP Proxy

The differences between SIP registrars and SIP proxies are worth noting, as the two terms often get conflated.

A SIP registrar focuses specifically on the registration process. It processes SIP REGISTER messages and maintains user location bindings in its database. The registrar also allows endpoints like phones and softphones to update their addresses if they get moved between different networks.

In contrast, a SIP proxy server routes all types of SIP messages to their next destinations. Additionally, while proxies may cache some location data, detailed endpoint tracking happens in registrar servers. These proxies are also vital when it comes to securing and encrypting your digital communications.

Note: To keep it rollin’ with less technical analogies, you can think of these two technologies in terms of a university directory.

For example, the registrar is like the university housing office, which tracks where each student lives every semester so that their mail can reach them. That said, whenever a student moves dorms, they need to register their new address with the housing office.

Meanwhile, the proxy is like the package delivery driver. It uses the available address info to pick up and route parcels to their final destinations all across campus.

Thus, in terms of VoIP infrastructure, registrars maintain the master directories for locating users, and proxies use this information to complete their voice and/or video call routing.

SIP Registrar Enabling Remote Work

At this point, you should have a good idea of why business owners choose to invest in the best business VoIP phone services, but it may not be clear how they make remote work easier.

Imagine a woman named Tina is a remote sales rep. She relies on video conferencing for meetings with clients and coworkers, and she connects with them by using a softphone app on her laptop.

When Tina boots up her laptop at a new location like a hotel or coffee shop, she first connects to the available Wi-Fi. Her softphone then sends a SIP REGISTER message to her company’s registrar server. This binds her current IP address to her AOR for the period dictated by the Expires header.

Now, whenever someone calls Tina’s office number, the central SIP proxy checks with the registrar to see where she is currently registered. If it finds she is located at her laptop’s public IP, it routes the call to it via the internet, allowing for a successful connection.

Without the registrar mapping her AOR to her laptop, calls would fail every time Tina’s IP changed. Thus, the SIP registrar gives Tina seamless mobility, which is crucial for making her remote work possible.

SIP users satisfaction graphic from Nextiva.

For Tina and other remote workers alike, there are several other advantages that a SIP registrar can offer:

1. Persistent Business Identity

With a SIP registrar, remote staff can use the same company phone number and extension regardless of where they are located. This means that even if they move between home and office networks, the registrar will automatically map their core ID to the current device.

2. Smooth Network Transitions

With SIP registrar technology, seamless registration happens as workers connect phone clients to new networks. This requires no manual reconfiguration, meaning calls will persist uninterrupted as employees switch between corporate LANs and home Wi-Fi networks.

3. Unified Communications (UC)

Companies can tightly integrate SIP registrars with leading UC platforms. Not only does this make it easier to collaborate through desktop and mobile communication apps, but the added visibility of present statuses also helps coworkers chat, view schedules, and call remote teammates on their own devices.

As businesses continue to support remote and mobile workers, SIP registrars will continue to be necessary for bridging networks and keeping employees connected wherever they are. Therefore, whether you’re a road warrior, a digital nomad, or even a home hermit, you can count on your SIP registrar to keep you online.

Make your website better. Instantly.

Over 300,000 websites use Crazy Egg to improve what's working, fix what isn't and test new ideas.

Free 30-day Trial