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©Stephen Kingham
SIP Peering
SIP Workshop
APAN Taipei Taiwan 23rd Aug 2005
By Stephen Kingham
mailto:[email protected]
©Stephen Kingham
This work is the intellectual property of the author. Permission is granted for this material to be shared for non-commercial, educational purposes, provided that this copyright statement appears on the reproduced materials and notice is given that the copying is by permission of the author. To disseminate otherwise or to republish requires written permission from the author.
Copyright Stephen Kingham 2004
©Stephen Kingham
Review Call Setup
SIP UA SIP UA
SIP Location Server
2. L
ook fo
r SRV re
cord
for f
linder
s.ed
u.au Call Control
Call Control andAudio and Video
SIP Redirect Server
DNS
3. INVITE
russ.nagel@flin
ders.edu.au
1. Register
Flinders University
Audio and VideoRTP UDP
©Stephen Kingham
• DNS is integral to SIP routing.• DNS is used to find a priority list of SIP servers for a
domain.• It does this by putting in SIP specific SRV records into
the DNS.• Just like MX records in DNS for mail.
• So it turns out it is easy to have backup servers in SIP.
• Good description found on the MIT Internet2 sip.edu project cookbook: http://mit.edu/sip/sip.edu/dns.shtml
SIP and DNS
©Stephen Kingham
• Specific SRV records added to your DNS for SIP,eg
IN A 192.94.63.28
;If we place the SRV record above the next line it fails to load
$ORIGIN aarnet.edu.au.
_sip._udp SRV 0 1 5060 ser.yarralumla.aarnet.edu.au._sip._udp SRV 1 1 5060 ser.nsw.aarnet.edu.au.
ser.yarrulumla.aarnet..edu.au. IN A 192.94.63.28ser.nsw.aarnet..edu.au. IN A 138.44.16.90
SIP and DNS
©Stephen Kingham
• On a unix host use the dig command:dig -t SRV _sip._udp.aarnet.edu.au
• You should get a response that has this in it:
;; QUESTION SECTION:;_sip._udp.aarnet.edu.au. IN SRV
;; ANSWER SECTION:_sip._udp.aarnet.edu.au. 333 IN SRV 1 1 5060 ser.yarralumla.aarnet.edu.au.
SIP and DNS TEST
©Stephen Kingham
• ENUM (rfc 2916) uses the DNS to find the full SIP address using a telephone number. ACA might have ENUM Tier 1 into Australia soon http://www.aca.gov.au/telcomm/telephone_numbering/enum_nsg2/.
SIP and ENUM
©Stephen Kingham
2. Today, many addresses
tel:+61-399636844
mailto:[email protected]
tel:+46-706051234tel:+61-399636844
Source: Patrik Fältström, Area Director Applications Area IETF, from ITU Tutorial Workshop on ENUM 8 Feb 2002 Geneva
©Stephen Kingham
2. With ENUM, only one
tel:+61-399636844
mailto:[email protected]
tel:+46-706051234
tel:+61-399636844
Give this number to friends:+61-399636844
ENUM
Source: Patrik Fältström, Area Director Applications Area IETF, from ITU Tutorial Workshop on ENUM 8 Feb 2002 Geneva
©Stephen Kingham
VoIP via PSTN to PSTN
DNS-Server
“ENUM”
SIP-Server
SIP-Server
Gateway
Gateway
Source: Patrik Fältström, Area Director Applications Area IETF, from ITU Tutorial Workshop on ENUM 8 Feb 2002 Geneva
©Stephen Kingham
ENUM in a nutshell
• take phone number +46-8-6859131
• turn into domain name 1.3.1.9.5.8.6.8.6.4.e164.arpa.
• return list of URI’ssip:[email protected]
• ask the DNS
mailto:[email protected]
Source: Patrik Fältström, Area Director Applications Area IETF, from ITU Tutorial Workshop on ENUM 8 Feb 2002 Geneva
©Stephen Kingham
• TRIP (rfc 3219) does for telephone numbers that BGP does for the entire Internet. Dynamic routing by advertisement!
• Presenter to review – BGP version 3– Traditional Telephone routing using static configurations– TRIP
SIP and TRIP (Telephone Routing over IP)
©Stephen Kingham
Peering in APAN - STATIC
• Project 1 of the APAN SIP Working Group
• Static entries in a central SIP Server at APAN.• Could be called “SIP Global Dialling Scheme (SGDS)”
– based on H.323 GDS– Central APAN SIP Server “relays” calls to the APAN
Member.– APAN Member must tell APAN the numbers they
support.
©Stephen Kingham
Peering in APAN – Private ENUM
• (not proposed yet).• APAN use a Private ENUM tree where APAN members
populate their E.164 numbers with NAPTR records that point to their SIP Servers.
• This would be used in conjunction with the “golden” ENUM DNS Tree.
• SIP Servers today can look up multiple ENUM trees!, see talk at APAN Taipei 2005 on Thursday.