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H.323 and SIP – VoIP Protocols Comparison

H.323 and SIP – VoIP Protocols Comparison

In recent years, the internet technology has grown in leaps and bounds. One major product of this technology is the Voice over Internet protocol (VoIP). VoIP is a technology that enables better audio and visual communication from our home computers. Through this, we can communicate easily from wherever we are and it is cheaper than the conventional telephone services. The upfront investment required for this is also very less. VOIP is still in its early stages and it has to undergo more development before it can substitute the regular telephone.

The two types of VOIP protocols used today are:

  1. H.323
  2. SIP


The more commonly used protocol. This was created by the International Telecommunication Union for the purposes of multimedia communication over IP networks.


  • Videoconferencing
  • Voice over IP

It is been designed with a number of means to recover connection failures. It has a number of alternate gatekeepers and endpoints which help to pinpoint the source of connection failure.

In the message encoding process, messages are encoded by H.323 into binary format and are decoded by using decoding machines. This binary format is suitable for both broadband and narrow band connections.

In load balancing process, endpoints report their total and available capacity to H.323, which distributes the calls equally across these gateways.

In call signaling process, the H.323 gatekeeper provides address resolution through RAS message exchange and routes the call signaling traffic.

In address resolution, the H.323 gatekeeper may use any number of protocols to discover the destination address of the callee, including LRQs to other gatekeepers, Annex G/H.225.0, TRIP, ENUM, and/or DNS.

New features are added to H.323 keeping in mind that backward compatibility is preserved.


The second type of VOIP protocol used is the SIP.

  • SIP was designed to setup a “session” between two points
  • It has no support for multimedia conferencing
  • SIP has large number of problems and has been deployed successfully only in PSTN gateways
  • Detection can only be done through timer expiration and re-establishment takes long periods

Like H.323, SIP also performs the functions of message encoding, load balancing, and address resolution.

In message coding, the message are coded into ASCII format and are too long. This makes it suitable only for broadband networks. Efforts are being made to encode SIP in binary format.

In the load balancing stage, SIP follows “trial and error” methods across different proxy servers available. If there is a timeout, then it shifts to another server.

In the process of address resolution, SIP has no address-resolution protocol. To check SIP advantages by yourself, try to use trial phone number by Hottelecom.


  • The main disadvantage of SIP is that it has no means to detect network failures
  • The processing requirements placed on the SIP proxy are higher than with H.323, which requires more message exchanges to pinpoint the position
  • Another main problem with SIP is that all the new versions are not backward compatible, which causes operational problems

Hence we see that in many ways, H.323 protocol is vertical and complex, but actually SIP is horizontal and more open. So SIP protocol pretends to be more promising, despite of disadvantages.

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Calling Card – Dos And Don’ts

A calling card has made a significant place for itself in the telecom industry. It is initially started as a method to avoid using coins in the local pay phones. Today, any type of call i.e. local, STD and ISD can be made from the prepaid calling card. The card can be operated from any phone even if the outgoing calls are barred on that phone. The bill amount for all the calls made is taken from your prepaid card amount and the rate per minute for any call remains constant throughout the day.

There are certain points which must be checked before one purchases a prepaid calling card:

  1. If the prepaid card is operational in the countries where one might travel. It must allow you to call back home from the foreign country.
  2. The calls rates to make and receive calls, duration of validity period and the provision to recharge the call internationally must be checked.
  3. To find out if there is any monthly fees for the card, the pulse rates for the call and if the call rate varies at different times of the day.
  4. Find out the difference in call rates to different countries of the world.
  5. Find out which other telecom companies the card provider has tie-ups with.
  6. Find out whether the bill increment system is based on minute billing or minute rounding method. In minute billing, there is a 1 min. pulse and bill is taken for total duration of the call only. In minute rounding system, if there is a 3 min. pulse and the call duration is 4 min., then the bill is charged for 6 min.
  7. Whether there is any charge for the calls that do not connect.
  8. If there are any hidden costs and taxes within the calling card amount.
  9. If the calling card customer service operator is available throughout the day.
  10. If the calling card company provides any guarantee and is trustworthy or not.
  11. How the prepaid calling card will be sent to you after purchase.

An international calling card is one that allows you to make calls to foreign countries at a price lower than normal ISD charges. The amount for each call to a foreign country is deducted from the prepaid card amount. The main point to be observed is whether the international calling card you are going to purchase can be used in the country of your frequent travel. You must also check the call charges from and to a country, both from your home country and the foreign country. Before traveling to a foreign country, it is a must to check the access code of the card with the retailer or Card Company.

Some More Tips

To avoid being billed any taxes on the card use, it is beneficial to purchase cards of smaller denomination and use up the entire amount in one call. You should not be billed extra amount for long calls if the call takes more than specific duration. If you use a card purchased from a company in one country, and use it to make calls from a payphone in a foreign country, a certain payphone fees is charged. It must be verified whether your calling card is exempted from this fees.

Some companies charge fees even at the time of disconnecting the calls, which is called the disconnection fees. These cards are better not purchased if you want to save money. The taxes levied on the call charges must also be checked. It is usually 5-15% of the call costs. Retailers usually do not mention about another type of fees called the maintenance fees, which is deducted weekly, bi-weekly or monthly. This is the fees the company charges for the maintenance of the card from the card-holders only.

Hence, you must verify all these features of different calling cards before you choose one that suits you best. It should be found out whether the card you purchase can be used in the countries you visit regularly. The card which you purchase should finally suit your needs and your way of lifestyle.

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