basics of protocols david duffett, aculab august 8-10, 2006 santa clara, california hyatt regency...
TRANSCRIPT
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
4www.voipdeveloper.com
August 8-10, 2006Santa Clara, California
Hyatt Regency Santa Clara
• 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
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August 8-10, 2006Santa Clara, California
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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
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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
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Introduction
Hello
Hello
Conversation
Goodbye
Goodbye
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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
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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
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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
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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
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Which protocol am I?
• 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
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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
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Which protocol am I?
• 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
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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
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Which protocol am I?
• 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
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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
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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
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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
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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