Frequently Asked Questions

With SIP trunks, voice gets converted into IP packets. These IP packets then get sent to the SIP provider (and vice versa). Because voice is real-time sensitive, it requires that the voice packets arrive within a certain amount of time and in the right order (along with a number of other factors like jitter, packet loss, etc). If some of the voice packets get dropped or if they are sent too slow, audible quality issues can occur. So the quality of the connection between the customer’s phone system and the SIP provider directly affects the quality of the call. The connection between the customer’s phone system and the SIP provider varies. It can be a direct connection or over the Internet. The Internet is essentially a “network of networks” in which all types of data traffic (voice, video, email, web, etc) travel. Because the voice packets are “co-mingling” with other packets carrying various forms of information for different customers, it is considered a “best effort” form of delivery. This is why a dedicated connection between the customer’s network and the SIP provider is “technically” the best method for delivering SIP trunks. If that dedicated connection is also going to be used to send other types of data traffic (web surfing, email, etc), it needs to prioritize the voice packets over all other data packets (this is called Quality of Service).

That being said, a dedicated connection to the SIP provider is often too expensive for smaller customers. Delivering SIP trunks over a high bandwidth / low cost Internet connection is popular due to the enormous cost-savings. MOST quality issues are a result of a “bottleneck” or too much data on the” last mile” of the Internet connection. The last mile is the connection between the customer’s network and their Internet Service Provider (ISP). This can occur if the customer is trying to place SIP calls over the Internet while downloading large Internet files (for example). Bottleneck issues can be resolved by asking the Internet Service Provider (ISP) to provide quality of service (QOS – the prioritization of voice packets over all other traffic). Low-cost / High bandwidth providers will usually not provide this service. Another option would be to install a separate, dedicated Internet connection for the SIP trunks. This eliminates any possible bottleneck issues (as long as the bandwidth can accommodate the number of simultaneous SIP calls needed). (See FAQ How much bandwidth do I need for SIP trunks?) Last, it is always a good idea to use a Tier 1 or Tier 2 Internet provider to minimize the “hops” or networks the call must traverse to get to the SIP provider.

The best way to finish answering this question would be to give real-world examples of our customers with varying sizes, Internet traffic, and call volume:

Very small company with light phone traffic: Many of our smaller customers (usually 5 or less trunks) or branch offices have provisioned their SIP trunks over the same broadband Internet connection they use for standard Internet traffic. Because Internet and voice share the same “pipe” the amount of Internet traffic that customer generates and the size of the Internet pipe can affect the quality of the voice traffic. If there are quality issues in these circumstances, the cause is usually found in that “last mile” or the connection from the Internet Service Provider (ISP) to the customer. If the Internet and voice traffic is light, this can be a very good (and very cheap) solution for the customer.

Small to medium-sized company with moderate phone traffic: We generally recommend that the company who needs over 5 trunks with moderate phone traffic install a dedicated broadband Internet connection. Because most quality issues arise in the “last mile” or the connection between the customer and the Internet Service Provider (ISP), keeping standard Internet traffic (which is bandwidth-intensive) and voice traffic separate is a good idea. This eliminates any issues that arrive due to Internet traffic interfering with the voice traffic.

Medium to large company with moderate to large amounts of phone traffic: In these circumstances, we usually recommend that the company install a dedicated connection between their premise and the SIP provider (ITSP). Often, the SIP provider can provide this connection by bonding T1s for larger amounts of bandwidth. The SIP provider can also provide Internet access with Quality of Service for voice over this connection as well. Again, depending on the amount of voice and Internet traffic, the recommended connectivity solution and design will change. We have large customers who already have large Internet connection (DS3, OC3, etc) in which they’ve chosen to provision their SIP trunks over. Although these forms of connectivity are more expensive than your typical DSL or cable, the cost savings are still substantial after you consider long distance savings, the elimination of copper trunks at remote offices (with SIP, those numbers can port to the corporate office), better use of bandwidth (twice as many SIP trunks can be provisioned over the same amount of bandwidth as traditional PRI trunks), and other cost-savings factors.

Well obviously the best connection is a direct link to the SIP provider. This isn’t always (more often than not) a very economical solution for the small office. Low cost / high bandwidth Internet connections (DSL and cable) are very popular for our customers with 15 or less trunks. Keep in mind, these Internet connections are low cost for a reason. You are sharing the access to that Internet connection with your neighbors. This introduces a number of factors outside your control that can affect quality – the number of neighbors, their Internet usage, the quality of the cable or copper, etc. Again, most quality issues we see are usually found in “the last mile” or the connection between you and your Internet Service Provider (ISP). We’ve seen issues with low cost / high bandwidth Internet connections in about 2 out of 40 customers who chose this method of delivering SIP trunks. One customer reported an occasional “echo” and the other customer complained of severe quality issues. It turned out that the customer who complained of severe quality issues was generating a substantial amount of phone traffic as they were a call center. However, we never got a chance to ascertain the actual problem as the customer migrated away from SIP trunks back to traditional carrier services.

Again, we have MANY customers doing this with no issues – and they’re enjoying tremendous cost savings! As mentioned above in the Quality section, we usually recommend a dedicated low cost / high bandwidth connection used solely for the SIP trunks (usually customers over 5 trunks). Internet connections with a direct connection to the ISP can be a very good alternative (and more expensive) to higher-call volume customers. Connections such as fiber, T1, and MPLS all fall into this category. Note these connections are still “best effort” as the voice traffic still traverses the wide-open Internet. Also, you need to consider the amount of standard Internet traffic you’re generating. We haven’t seen any issues with fiber or Internet T1s.

We don’t recommend a wireless Internet connection. Unfortunately, the amount of packet loss and delay in these connection methods can severely affect quality.

This depends on the type of codec (the mechanism used to compress the voice traffic over IP) and the number of simultaneous calls. Broadvox uses G.711 and G.729. G.711 is considered “higher quality” and usually consumes about 88 Kbps (with overhead). G.729 consumes about 38 Kbps. Most of our customers choose the G.729 codec because they get more use out of their bandwidth. We personally cannot hear the quality difference between the two codecs.

This depends on the SIP provider. Broadvox allows for month-to-month, 1-year, 2-year, and 3-year terms. Month-to-month contracts require that the customer pay monthly with an automatic credit card deduction.

Yes, one of the fantastic things about SIP is that you can source or port numbers from any state to your SIP trunks (regardless of where the SIP trunks are terminated). However, there are a few areas in the country where not all numbers can be ported. Check with Access Technologies or an Access Technologies Agent to be sure. This also depends on the SIP provider.

That varies by the SIP provider and the location of the customer. We usually estimate about 12% of the total monthly billing with Broadvox. However, we’ve seen it higher. Normally the miscellaneous fees and taxes are much less than traditional carriers.

Yes. Pricing usually depends on the SIP provider and term.

Many SIP providers will bundle a large number of local calling minutes into a flat price. If the customer exceeds these minutes, they get billed per minute for the additional local minutes. This doesn’t sit very well with companies who are used to unlimited local calling. That’s why we like Broadvox. Broadvox will charge a flat rate per SIP trunk with unlimited local calling.

Yes. Often for a lot less per minute too! The pricing varies by the country called.

Actually, 911 works very well. With Broadvox, it’s all about the number that is out-pulsed from the customer’s telephone system (which is usually easily configurable in the phone system). The number out-pulsed has to be a 911-registered number with Broadvox. The following examples illustrate this:

BTN – Billing Telephone Number: All Broadvox BTNs are 911-registrable. Usually the BTN corresponds with the physical address of the company. If a 911 call is placed from the corporate office, the phone system will send the BTN, thus emergency personnel will show up at the correct address.

EDID- Enhanced DID: This is a Direct Inward Dial (DID) number with 911 registration. For example, a home worker places a 911 call with their IP phone. The phone system is programmed to out-pulse that EDID number, which is a 911-registered address with Broadvox. That number corresponds to the physical address of the home worker – not the main office (which is where the SIP trunks are terminated).

It is very important to note that you must coordinate with Broadvox to register the appropriate address and have it correspond with the phone number. It is equally important to program the telephone system to out-pulse the appropriate caller ID. Always test this during the phone system installation.

No, with Broadvox, SIP trunks can be provisioned with a dynamic IP address using registration.

Absolutely. With Broadvox’s GoDomestic product, you only pay for the minutes used, not on a per-trunk basis. You can have as many simultaneous call sessions as your bandwidth can handle. This is very popular for outbound call centers and schools who don’t use their phone lines during parts of the year.

The answer depends on the SIP provider. We’ll answer this question with Broadvox capabilities:

• The ability to provide a primary / secondary configuration to two SIP trunks
• The ability to load balance to multiple IP addresses on the customer’s end. Concurrent call sessions (per trunk) must be split between IP addresses.
• The ability to perform fail-over to a POTS line or cellular number if the SIP trunk goes down
• The ability to automatically fail over between separate Internet connections using SIP registration.

Note: Fail-over capabilities also depend on the phone system and/or network equipment deployed. We’ve seen in work natively with some phone systems and we’ve seen additional routers that had to be installed with others. We highly recommend you test all SIP capabilities, including fail-over, with your particular brand of PBX.

Again, this depends on the SIP provider. We’ll stick with the Broadvox answer. Like 911, it all depends on what number is out-pulsed to Broadvox. The following Broadvox products support local calling:

• BTN – Billing Telephone Number: All Broadvox Go! Trunks include one BTN. All outbound calls with the BTN as the caller ID receive unlimited local calling to the calling area of the BTN.
• ELN- Enhanced Local Number: This is an additional number that can be purchased from Broadvox. Like the BTN, all outbound calls with the ELN as the caller ID receive unlimited local calling to the calling area of that ELN. For example, a customer in Portland, Oregon has Broadvox SIP trunks. All calls to Phoenix have a Phoenix ELN as the caller ID. Broadvox sees this ELN and rates the call as local. ELNs also receive 911 registration from Broadvox.
• GoAnywhere Trunks: Since GoAnywhere trunks provide unlimited local and long distance calling in the United States (lower 48 states) and Canada, it doesn’t really matter what number is out-pulsed from the phone system to Broadvox.

Note: It is important to note that Broadvox will allow the customer’s phone system to out-pulse any 10-digit caller ID (7 digit dialing is not supported). However, if the number is not a BTN or ELN, the call will be rated as long distance (if the call is placed over a GoLocal SIP trunk). If the customer purchases VDIDs (Virtual DIDs), and out-pulses the VDID caller ID, Broadvox will still meter the call as long distance. VDIDs are primarily used for inbound calling. The BTN and ELN have to be Broadvox numbers, all others will get metered at long distance rates.

Different SIP providers are certified to work with various IP phone system manufactures. Some IP phone system manufactures require additional equipment to operate. Check with an Access Technologies representative to determine if your phone system is certified.

Note: It is important that you test your phone system EXTENSIVELY with the SIP provider before implementing production systems with SIP. Often, demo trunks can be ordered on a monthly basis for this purpose. Test all important features like call forwarding, conferencing, transferring, etc. Often a phone system can be “certified” but certain features can be missing. As an agent, we’ll try to get you in touch with another agent who is using the same type of phone system for technical / feature discussions.

No. We have many customers that use an Integrated Access Device (IAD) that converts the SIP trunks back to traditional analog or PRI connections.

This depends on the SIP provider. Broadvox can implement SIP trunks over a dedicated or VPN-enabled connection. Actually, it’s much harder for somebody to intercept a VOIP call than a traditional PRI or analog call. To intercept a traditional Public Switched Telephone Network (PSTN) call, the hacker only needs limited telco knowledge and access to the building junction box. To hack a VOIP call, the hacker must have significant networking knowledge as well as hack one or more networks that have been deployed with ample security precautions.

Yes, most SIP providers support G.711 or T.38 faxing protocols. We’ve been told that faxing over SIP trunks is about 95% reliable. For this reason, we generally recommend that our customers keep faxing off SIP trunks and on analog lines (which is great for a back-up line anyway). This may change as we feel more comfortable with it.

Yes, using SIP registration, this is possible.

Yes. We often mix long distance SIP trunks with local SIP trunks. By least-cost routing long distance calls over the long distance trunks, you save the maximum amount of money.

Note: With Broadvox, you must purchase three minimum of any flavor of SIP trunks. If you wanted to purchase their long distance (GoAnywhere) and local (GoLocal) products, you would need three minimum of each.