basics of protocols david duffett, aculab august 8-10, 2006 santa clara, california hyatt regency...

Basics of protocols

David Duffett, Aculab

3www.voipdeveloper.com

August 8-10, 2006Santa Clara, California

Hyatt Regency Santa Clara

Our agenda for today

• Introduction• Background• A quick game of ‘which protocol am I?’• Strengths and weaknesses• Real life examples




• Clasp your hands in front of your face• Which thumb is closest to your face?

• Left thumb closest– You are the sexy people

• Right thumb closest– You think you’re the sexy people

But first … a quick test




Introduction

• What is a protocol?– pro·to·col (prọ tọ -kôl) n. – The forms of ceremony and etiquette observed by

diplomats and heads of state– A preliminary draft or record of a transaction– The plan for a course of medical treatment or for a

scientific experiment– Computer science – a standard procedure for regulating

data transmission between computers




Introduction

• In the crazy world of VoIP…– We can generally take ‘protocol’ to mean the way in

which the calling and called end points must communicate with each other in order to set up, tear down and otherwise manage a session (call)

– There are a number of these protocols– Even having two end points claiming to use the same

protocol is not a guarantee of a working solution– People interpret the ‘standards’ for their own purposes




Introduction

Hello

Hello

Conversation

Goodbye

Goodbye




Background

• As VoIP has developed, various protocols used for call control have appeared– Telecoms standards bodies– Internet standards bodies– Individual developers trying to solve a problem– Commercial entities




Background

• For VoIP to work, both (all) the end points involved must use the same protocol for call control – unless a gateway is in use




Which protocol am I?

• Developed by a telecoms standards body• Based on the tried and tested Q.931• Adopted in early VoIP deployments, I am still very

much in use today• I am very efficient in that I use short codes for

messages• Some of the really big players developed their

systems around me




Yes – I’m H.323

• Developed by the ITU• Very ‘telecomsy’ way of doing things• Good record on compatibility• Cisco were heavy H.323 users• Early protocol, but still very much in use• Used for video sessions, as well as voice





• Developed by an Internet standards body• Arrived at by successful RFCs• Most VoIP developers talk about me• I use messages that humans can easily understand• Some backbone networks are based on me• I am very flexible, useable for more than just voice




Yes – I’m SIP (session initiation protocol)

• Developed by the IETF• People contribute RFCs, once agreed they become

part of the ‘standard’• Probably more SIP end points than anything else• BT’s 21CN is based on SIP• Amazing potential with 3PCC (third party call

control)• The initiated session may be used for voice





• Originally developed by an individual• My name references an Open Source PBX• I am bandwidth efficient• A lot of end points are capable of supporting me,

even though the big players don’t yet use me




Yes – I’m IAX2 (pronounced ‘eeks’)

• Originally developed by Jared Smith, an Asterisk developer

• Full name is Inter-Asterisk eXchange version 2• Ongoing development encouraged within the Open

Source community• Aggregates RTP payloads together in order to

make more efficient use of the packet headers, and therefore bandwidth





• Developed by a commercial organisation• I am probably the most widely used protocol today• I have been described as a ‘car with hood welded

shut’• I enable peer-to-peer voice and video

communications• I am probably the most widely known VoIP brand




Yes – I’m the Skype protocol

• Developed around 2003 by the people that brought us the KaZaa file sharing service

• Uses an overlay peer-to-peer network made of ordinary hosts and supernodes

• Very little is known of the details of the protocol• Great at traversing NATs and firewalls• Over 100,000,000 downloads to date




Real life situations

• Person away on business wants to communicate with their spouse from hotel room– Skype would allow voice and video

• Same person wants to call normal landlines– Skype Out (costs)– ATA – using IAX2 would remove NAT hassles

• Telco wants multi-functional network and the ability to separate voice and call control signalling– SIP




In summary

• VoIP call control protocols are used to set up, tear down and otherwise manage calls

• H.323 – well deployed, but not seen as the future• SIP – all the talk is SIP, has trouble with NATs and

firewalls• IAX2 – popular with Asterisk installations, on the

ascendancy and bandwidth-efficient• Skype – the most popular, but bespoke and only for

peer-to-peer




In summary

• Choice of protocol must be a function of requirements, both now and in the future

• Safe bet is to go with equipment that can support multiple protocols and codecs

Thank you

[email protected]

See us at booth 115

basics of protocols david duffett, aculab august 8-10, 2006 santa clara, california hyatt regency...

Documents

use slide

aculab slide

voice slide

purposes slide

quick test slide

users early protocol

protocol pr t

introduction background