Now that we understand what a protocol is and how important they are to the entire process, we can take a closer look at the specific protocols VoIP utilizes. There are quite a bit out there, and many have come and gone over time. However, for the vast majority of users, there are only two main protocols to focus heavily on.
The most popular protocols currently utilized for UC are SIP (Session Initiation Protocol) and H.323. If youíve taken a look at some of our provider head to heads, you may have noticed that some providers will specifically offer SIP Trunking capabilities. Beyond this, VoIP can utilize other protocols like MGCP and SCCP, but we will go more in depth with those further down. You can click here to skip down there now.
Intelligent Endpoint Protocols
The name Intelligent Endpoint Protocols is used to describe SIP and H.323 because all of the ìintelligenceî necessary to locate the receiving device and establish the data transfer between your device (the local host) and whomever you are calling (the remote device) is baked right into the protocol.
Both SIP and H.323 are the most popular protocols youíll come across, having originated in 1995 and 1996 respectively. Itís fairly safe to say, though, that H.323 has grown to be more popular than SIP in recent years. However, this isnít to say that H.323 is objectively better. In fact, itís hard to come to that conclusion: both protocols do the job, and both do the job well. At the end of the day, like most things, it will come down to what your business specifically requires.
The Current Standards: SIP vs H.323
This topic has pretty much been beaten to death all around the internet. As we previously stated, there isnít necessarily one protocol that is better than the other. However, it is still important to understand how each protocol operates, how they differ, and when it makes sense to use one over the other.
The Basic Definitions, and Concepts
Session Initiation Protocol:
The Session Initiation Protocol has become the Internet Engineering Task Force (IETF) standard for multimedia sessions. The IETF is really just a large, open international community comprised of almost anyone involved in networking, including designers, operators, vendors, and researchers focused on the evolution of the Internet. The IETF has determined SIP to be a standard for audio, video, and even instant messaging or team messaging solutions.
It is interesting to note that SIP is modular, meaning it can be changed around. Depending on the type of data you wish to transmit, your SIP deployment will need to be designated for that specifically. Therefore, VoIP and IM communications will work around different aspects ó and this is a major strength of SIP. Itís less of a one-size-fits all approach because it can be designed specifically for one approach.
On the other hand, the H.323 protocol has become the international standard for multimedia communication over ìpacket-switched networks.î This can include Local Area Networks (LANs), Wide Area Networks (WANs), and even the general internet we all connect to. Essentially, H.323 can be seen as an ìumbrellaî that includes multiple standards: H.323, H.225.0, H.245 and H.460. H.323 is an older standard, and a very large part of it was based on the ISDN standards.
Donít worry too much about what that means: it was simply the set of standards for legacy and traditional phones that communicate over the PTSN. H.323 focuses on covering real-time voice, video, and data communication, and was designed specifically to operate over IP networks. Although not widely used, H.323 was also designed with voice and video conferencing capabilities. At this point, H.323 has become the world market leader for voice and video over IP communications (that means your VoIP system) and is even utilized in enterprise video conferencing solutions.
How Do They Differ?
First off, H.323 was based off of the binary language using 1ís and 0ís. SIP, on the other hand, has a simpler text-based format ó much like the HTTP that powers pretty much all websites. In fact, a lot of the technology used to support HTTP was utilized when developing SIP. The differences between the two are bigger than that, though.
H.323 was developed by the International Telecommunications Union ó the organization responsible for building the Public Switched Telephone Network we use for landlines and legacy phones. Developed with video conferencing in mind, it naturally lends towards voice as well.
SIP was developed, and is currently controlled, by the IETF as we mentioned above. This organization is responsible specifically for the protocols and overall functionality of the internet. SIP was designed to add a new flexible and modular layer to the internet.
Phones and Flexibility
H.323 is mostly a proprietary solution at this point, and explains why providers will require users to purchase their specific phones to ensure all functions and features work.
SIP, on the other hand, is much more flexible and generally any SIP phone will operate fully on almost any SIP network. Providers try to prevent this, but itís mostly possible.
H.323 works very well for voice and video communications. Based on an original PTSN protocol, it makes sense for users to expect the same level of reliability and standard calling features. However, it has not expanded much beyond video or voice.
SIP, being modular, is what some refer to as ìmedia agnostic.î SIP does not necessarily require a specific type of data to be transferred; therefore, it can be utilized for instant messaging, presence indicators (who is online and who isnít), and even file transfers along with, of course, video and voice.
Ultimately, the end user will never really notice a difference between the two: both will make and receive calls, and function exactly as they should. However, with their origins being different and each focused on different tasks originally, itís easy to understand where drawbacks could appear for each.
H.323 works very well for VoIP and video conferencing, and is utilized by most providers for these needs; however, it has not been updated much in the last 10 years and doesnít power the ever-popular team messaging.
SIP has more flexibility and, therefore, more use cases with even more features and functions available. Overall, it has a wider range of functions, and while less specifically focused on voice calls, itís still completely capable.
What Other Protocols, Standards, and Definitions Should I Know?
While SIP and H.323 are probably the most common and popular protocols, there are other options that exist. Beyond this, there are a number of standards and terms thrown around that can become confusing quickly.
Telephony Gateway: These gateways are the network elements that simply convert audio signals carried on the PTSN to data packets transferred over the internet, or your LAN.
MGCP: The Media Gateway Control Protocol is simply a call control protocol, also known as a signaling protocol, utilized in VoIP systems. This protocol mirrors the structure of the standard PTSN.
Call Agent: Simply put, a ìcall agentî element is required in VoIP to deliver specific services to users and control the signaling communications between phones. Call agents instruct phones to provide dial tone and provide the heavy lifting with functions like phone number switching logic, call control, and endpoint registration.
H.248, or MEGACO: Developed by Cisco as an alternative to H.323, H.248 implements the media gateway control protocol to provide telecommunication functions and services across both modern packet networks (like the Internet or your LAN) and the PTSN.
SCCP: Also known as SKINNY ó a term that generally refers to a device that has cut out the fat ó it possesses less features and functions, but has the same core elements. When it comes to VoIP, though, SKINNY is a proprietary and Cisco-specific protocol. SCCP was developed for IP Telephony PBX PBA Doha Qatar specifically, but has integrated video. SCCP employs a ìcentral call agent,î which allows for very advanced and complex call features. SCCP requires that the call agent aspect always remain available to provide call features, which makes SKINNY a less than suitable option for implementations that require endpoints to function independently from a call agent.
What Does The Future Hold?
Of course, this doesnít tell the whole story, and a number of alternative protocols and standards do exist. In modern times, SIP and H.323 are the most widely adopted and utilized standards worth focusing on; however, that will change very soon.