university of wollongong australia the institute for telecommunications and information technology...
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University of Wollongong AUSTRALIA The Institute for Telecommunications and Information Technology Research (TITR) 3 Research at Wollongong u Wollongong University is regarded by the Industry as Australia’s premier IT&T R&D site The Institute for Telecommunications and Information Technology Research (TITR) operates within the University TITR has successfully undertaken over $13 million worth of R&D for Industry during the past 5 years Around 50 full time researchers (including graduate students) Major industrial funding sources include: Telstra, Motorola, Vodafone, Ericsson, BNR Research areas: QOS issues for fixed and mobile networks, Audio coding, SecurityTRANSCRIPT
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
1
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Call Setup Delay Modelling for Internet
Telephony
Dr. Tony EyersTITR
University of WollongongAustraliaJune, 1999
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
2
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Where is Wollongong?
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
3
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Research at Wollongong Wollongong University is regarded
by the Industry as Australia’s premier IT&T R&D site• The Institute for Telecommunications and
Information Technology Research (TITR) operates within the University
• TITR has successfully undertaken over $13 million worth of R&D for Industry during the past 5 years
• Around 50 full time researchers (including graduate students)
• Major industrial funding sources include: Telstra, Motorola, Vodafone, Ericsson, BNR
• Research areas: QOS issues for fixed and mobile networks, Audio coding, Security
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
4
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Internet Telephony QOS Major focus on protocol development
• H.323, SIP/SDP• RTP• Gateway Location Protocol (GLP)
Variable QOS• As yet, no standard definitions• IETF work underway to adapt ITU performance
targets Current work on Internet voice QOS
• focus on UDP delay over public Internet Current work on Internet call setup
delay• some IETF drafts on IP signalling transport• [Elawid97] considers delay performance of a
Lucent H.323 exchange
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
5
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Problem Statement Determine Internet Telephony Call
Setup delay distribution, over public Internet• Measure Post Dial delay, ie between sending
Setup message and receiving Alerting message
• Key parameters- propagation delay- queueing delay- retransmission delay
• Processing delay not considered• Aim: compare SIP and H.323 setup delay
performance- key difference: recovery scheme for lost messages- SIP uses UDP, with timeout/retransmission mechanism- H.323 uses TCP
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
6
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Current Objectives for Call Setup Delay
ITU Rec E.721 (1988)• Mean post dial delay 3 seconds• 95th percentile for further study
ITU rec Q.709• maxm number of STP/SPs for national/international
component of connections ITU rec Q.725 (and Telcordia GR-1364)
• mean and 95th percentiles for switch response delay (ie IAM, ANM message processing)
ITU Q.706• STP message transfer delay
New IETF draft combines these to form call setup delay targets• eg large country: 95% of connections have mean of
3040-3158 msec, 95th %ile 3947-3615msec
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
7
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Call Setup Delay Observations
Signalling Queueing delay not included in IETF draft• Queueing delay includes
transmission/retransmission delays• SS7 queueing delay targets outlined in ITU
rec E.733 IETF call setup delay target implies
routing and resource reservation My study ignores these, focuses on
queueing delays only• results provide a lower bound for Call Setup
delay
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
8
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Call Setup: SIP
INVITE
PROVISIONALRESPONSE
Message losttimeout
INVITEPROVISIONALRESPONSE
Call Established
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
9
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Call Setup: SIP Provisional response retransmissions
prompted by INVITE arrivals• an optional mechanism is provided for
provisonal response timeouts Final response messages always
timeout• Final responses also retransmitted when
retransmitted INVITES arrive SIP timeouts
• 500 msec initially• Retransmissions increase timeout by factor of
two• Maximum value 4 seconds• Retransmissions stop after 7 attempts
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
10
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Call Setup: H.323 (Fast Connect)
TCP SYN
TCP SYN
TCP ACK
SETUP
CONNECT
CallEstablished
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
11
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
H.323 Call Setup TCP connection establishment adds
additional round trip• propagation delay• SYN retransmission delay
SYN, SETUP, CONNECT use ‘standard’ TCP timeouts
TCP timeouts• Recommended initial value 3 seconds (RFC 1122)• Some implementations start at 6 seconds
[Stevens94], Solaris allows initial timeout to be set
• Timeout value increases by a factor of two for each retransmission
• Maximum number of retransmissions varies between implementations
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
12
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Simulation: Modelling Scenarios
1) SIP: INVITE - Provisional Responsemessages can pass through stateless proxies
2) SIP: INVITE - Redirect Server, then INVITE - Provisional Response
3) H.323 Fast ConnectTCP connection setupExchange H.323 SETUP/CONNECT messagesTCP timeouts assumed to be the same as the
SIP ones
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
13
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
UDP Delay: the Surveyor Project
Run byAdvanced Networks and Services Measures one way UDP delay
• Currently 38 sites (mostly USA, some in Europe, Korea, New Zealand)
• Each site exchanges 4x40 byte UDP packets each second (2 each way)
• One way delay measured, resolution 50 usec• Packet loss also recorded
Surveyor site provides• delay/loss histograms for each day, for all site
pairs (measurements began in 1997)• located at http://www.advanced.org/csg-ippm/
Have been able to access the Surveyor traces for this project• provide delay/loss for each UDP packet
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
14
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Simulation Methodology Periods of up to 1 hour are examined Instantaneous Delay/Loss probabilities
constructed from trace records• two state error model used• 200 sample and 20 sample moving windows
maintained- if 20 sample window has one error or less, current error prob.
calculated from previous 200 samples- otherwise bad state assumed, error prob. calculated from 20
sample window
Simulated Calls then arrive• 50/sec, poisson call arrivals
Call Setup Delay distribution/Call loss rate recorded over simulated interval
Statistics for a one hour period generated from 6000000 calls
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
15
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Case Study Simulation runs over the first 90
business days in 1999• 60 minutes per day starting at 16:00
Source Destination pairs• New York-Boston• New York-Chicago• New York-West Coast• New York-Hawaii
Variations• All calls visit a redirect server in Washington DC • All calls visit a redirect server in Washington DC,
then transit a proxy server in Indiana• H.323 (eg TCP)
Plots show 0th percentile (‘+’) and 95th percentile of call setup delay (‘o’)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
16
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Boston
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
17
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Chicago
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
18
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/West Coast
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
19
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Hawaii
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
20
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Boston (DC redirect)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
21
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Chicago (DC redirect)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
22
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/West Coast (DC redirect)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
23
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Hawaii(DC redirect)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
24
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Boston(DC redirect,via Indiana)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
25
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Chicago(DC redirect, via Indiana)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
26
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/West Coast(DC redirect, via Indiana)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
27
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/Hawaii(DC redirect, via Indiana)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
28
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/BostonTCP comparison
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
29
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/ChicagoTCP Comparison
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
30
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/West CoastTCP Comparison
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
31
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York/HawaiiTCP Comparison
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
32
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Conclusions 95th percentile of Call setup delays
mostly under 1 second• relatively small sample• missing days may hide poor results• relies on error probability modelling assumptions
95th delay percentile determined by error threshold• as additional paths are added (ie redirect
servers/proxy servers), increased error probability eventually raises 95th percentile
TCP shows, in some cases, a marked increase in 95th delay percentile• due to increased error probability arising from
connection setup• TCP delay will increase markedly if standard TCP
timeout values used
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
33
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
Future Work This project
• Extend experiments to consider- TCP/UDP performance during very high error periods- Full H.323 call setup
• Develop analytical model for delay/loss- based on mean error rate
• Determine effect/prevalence of bursty errors Related Projects
• Determine targets for signalling message transport delay (as a component of overall call setup delay)
• Design procedures for dedicated IP signalling networks
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
34
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York-Indiana
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
35
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York-Boston(error window =600)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
36
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York-Boston(error window = 4)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
37
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York-Chicago(error window = 600)
University of
Wollongong
AUSTRALIA
The Institute for
Telecommunicationsand Information
TechnologyResearch
(TITR)
38
T H E I N S T I T U T E F O R
T E L E C O M M U N I C A T I O N S
R E S E A R C H
New York-Chicago(error window = 4)