VOIP

1. VOIP ENGR 475 – Telecommunications Harding University November 16, 2006 Jonathan White

2. Outline • Functionality • What it runs over • Benefits • Cost • Flexibility • Quality • Security • Drawbacks • Hurdles that need to be overcome • Adoption rates • Legal issues

3. VOIP • VOIP: Voice over Internet Protocol. • A method for routing voice calls across the Internet, instead of the PSTN. • Your voice is packetized and sent across the Internet. • No longer circuit switched. • Main benefit: • You have a telephone wherever you have an Internet connection • You can bypass the PSTN, and its charges.

4. VOIP Access Methods • Computer to Computer: • Skype, free, closed source, security by obscurity, potential bandwidth issues. • Requirements: • Software, microphone, speakers/headphones, soundcard, connection to the Internet. • No charges ever involved. • Does it matter how far away a website is? • Easiest method. • But, who wants to be on a computer all the time to make a phone call?

5. VOIP Access Methods • ATA: Analog Telephone Adapter. • Your analog telephone is connected to a special device that connects your phone to the Internet. • Just looks like a DSL router. • This is typically what Vonage sends you when you buy service from them. • $20 a month for Vonage service, with deals similar to cell phone plans. • Inexpensive, typically $50 for the Adapter.

6. VOIP Access Methods • IP Phones • Look like normal phones, except they use an RJ-45 (Ethernet) jack instead of an RJ-11. • Connects to your router or switch. • All the necessary hardware and software is on the phone when you buy it. • Phones cost $150 and up • Combination of the ATA and analog phone.

7. Packet Switching • Most PSTN network trunks are becoming packet switched. • Why? • Voice providers are carrying more data than they are voice. • Most calls today get sent across a packet switched network at some point already. • However, there can be a large lag time: • 600 ms for a call in China from the US • As time goes on, many predict that voice will just be another application on the Internet. • This is already true to some extent.

8. Nokia E61 • Dual Mode with WiFi and 3G CDMA support: • At home or where ever there is a wireless Internet connection, the phone uses VOIP to communicate for free. • Where there isn’t an Internet connection, it accesses the cellular network. • Both have high data transfer rates. • Is this the future of telephony? • Is this the future of computing?

9. Benefits of VOIP • Free or nearly free calls to other VOIP users. • No long distance • Every feature imaginable is free or nearly free: Call waiting, ring tones, call forwarding, etc, etc, etc. • Quality can actually be quite good. • Better than cellular calls. • On par with landlines.

10. Benefits of VOIP • Large installed base of packet switched networks get to be used more fully. • Voice data gets compressed from the beginning. • When no one is talking, no packets are sent. • Voice is encrypted from the beginning. • You can get a phone number for free. • You can receive calls anywhere where there is an Internet connection. • Your landline phone is no longer stuck on land.

11. How a VOIP call works • You have an IP address and probably a telephone number on your ATA or IP phone. • Dial who you want to talk to. • The phone number is sent to your VOIP provider’s call processor. • Large database that maps IP address to phone numbers and back and forth. • A session using a protocol called SIP ( or H.323) is used to essentially connect the 2 computers. • Much like the HTTP protocol. • You then can talk with your voice being carried on the Internet. • The data network can’t tell the difference between your voice and a webpage.

12. VOIP Drawbacks • Can’t send a fax with VOIP. • Dependent on wall power. • Dependent on an Internet connection. • Added one more database dip to the telephone system. • Latency and Jitter. • Must use voice buffers on both end. • Packet delay can be a maximum of 600 ms if using a satellite link.

13. VOIP Drawbacks • Packet loss. • Your data network must be non-congested. • UDP is used in some implementations, which doesn’t guarantee delivery of packets. • Reliability of your Internet connection • Especially compared to your landline phone. • 911 doesn’t work at all or it works poorly. • In 2005, the government made VOIP providers: • Support CALEA (wiretapping) • LNP • Payment of Universal Service Fees

14. VOIP Drawbacks • In developing countries, cellular phones have nearly complete market penetration. • Is there a need for a VOIP phone? • VOIP numbering schemes and protocols are not interoperable. • VOIP is still a developing technology. • Some devices depend on having a telephone grade connection. • TIVO, home security systems, some digital TV services • Operating systems of VOIP users. • Has your computer ever had a virus? • Has your landline ever had a virus?

15. VOIP Codec • Called G.723.1 and it is a descendant of PCM. • Samples at 8000 times a second. • Uses LPC (like a cell phone), so it doesn’t send the actual samples. • The look ahead is 7.5 ms. • Packages voice in samples of 30 ms. • The codec only takes up 2.2 Kbytes of RAM in execution.

16. VOIP Protocols • 2 Main protocols: • H.323 • Primary protocol for backbone networks. • Doesn’t handle firewalls well. • SIP • Session Initiation Protocol. • Used by end nodes. • Text based protocol, similar to HTTP • Uses TCP and UDP over port 5060 to connect to SIP servers. • Highly centralized, like the telephone network.