voip forum july 16 -17 (c) 1998 all rights reserved, hitachi, ltd.1 voip voice stream multiplexing...
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July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
1
VoIP Forum
VoIP Voice Stream Multiplexing
VoIP ForumHonolulu, Hawaii
July 16, 17
Tohru HoshiKeiko Tanigawa
Systems Development LaboratoryHitachi, Ltd.
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Table of Contents
Issues on Voice Streaming multiplexing pointed out last meeting Additional delay? Additional packet loss? Effectiveness of multiplexing? Architecture and protocol requirements
not to have constraints on multiplexing sequenceto have H245 capabilities exchange to indicate support of
multiplexing
Multiplexing FormatSummary and Future Work
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Network Topology of IP-GWs with multiplexing
PSTN
Phone
IP-GWPSTN
Internet
PSTN
IP-GW
Phone
Multiplexed voice stream channel
Single stream channel
IP-GW
PC (H.323)
.
.
.
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Overhead Reduction and Packet reduction
Discussed in last Portland meetingResults shows
Packet overhead is reduced to about 2/3
Packets are reduced to 1/ number of multiplexing
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Header overhead reduction(example calculation)
(kbps)
Number of simultaneous connections(streams)
20
120
100
80
60
40
1 2 4 8
non multiplex
multiplex 8 streams
Bandw
idth
use
d
Option 1
Option 2
multiplex 4streams
Option 1
Option 2
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VoIP Forum
Additional delay?
Originating sideNetwork sideTerminating side
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VoIP Forum
Additional delay? :Originating side
Coding delay : no additional delay Additional multiplexing processing delay caused
by multiplexing interval multiplexing interval is set to equal to or less tha
n framing or packetizing interval• G.723.1 framing and packetizing interval 30ms• G.729 framing interval 10ms, packetizing interval 20ms
Additional delay = multiplexing interval less than 10s ms
• example of multiplexing interval: 10 ms, 20 ms, 30ms
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Additional delay? :Network side
Store and forward delay in Router store and forward delay = packet
length/line speedComparison in 1.5Mbps line:
• non multiplex mode : 0.3ms/hop • 8 multiplex mode : 1.5ms/hop •Additional delay is 1.2 ms/hop
IP-GW IP-GWPhone Phonerouter router
Line speed
10Mbps 10Mbps
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Additional delay? :Network sideTra
nsm
issi
on
dela
y/h
op
(st
ore
an
d f
orw
ard
dela
y)
2
4
6
8 m
s
128 384 768 1544 kbps
8 mux
3 mux
Non- mux
Additional delay
ConditionsG.723.1 5.3kbps framing interval 30mspacketizing interval 30msmultiplexing interval 30msVoice 20B no silence compressionIP+UDP 28BRTP 12BMux-H 2B
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Additional delay? :Termination side
Additional storing delay is less than 1 ms because of 10 Mbps/100Mbps connected fast LAN speed.
No additional delay is introduced by de-multiplexing
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Additional delay? :Conclusion
Originating side: cause: multiplexing delay
10s ms (example: 10 - 30 ms) Network side:
cause: store and forward delay1.2 ms/hop (in case of 1.5Mbps line)
Terminating side: cause: storing delay
negligible small
Over all Additional delay caused by multiplexing is several 10s ms a
nd this is rather small compared with the internet delay of several 100s ms.
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Additional Packet Loss?
Additional packet loss introduced by channel bit bit error rate(BER)
Additional packet loss introduced by packet loss in router
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Additional Packet Loss? (cont.) Packet Loss by BER
BER is proportional to packet length
packet loss rate caused by BER Non-mux :P1 =480*p 3 Mux :P2= 1008*p 8 Mux :P3= 2288*p
Discussions Multiplexed stream has higher packet loss rate, but less than the rate of n times of non-mux mode Since BER is less than 10-6, then packet loss introduced by BER is negligi
ble small (compared to Internet’s packet loss of 10-1-10-2)
Voice packet
Length i bit
BER:pPacket Error Rate:PP = 1 - (1-p)i
= nearly 1-(1-ip) = ip
1 4 8 # of mux
Com
pari
son
of P
P=
Pi/
P1
1
4
8
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Additional Packet Loss? (cont.)
Packet loss in nodes Large packet loss in the Internet seems to be introduced
in routers
Reason is overload burst packet traffic to the routers Overload condition occurs based the number of packets Multiplexing mode will reduce the number of packets to
the nodes and this will improve overload condition and reduce packet loss
Conclusion Packet loss rate in multiplexing is nearly the
same compared to non-multiplexed mode.
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Effectiveness of multiplexing?
In case of concentrated traffic on certain IP-GWs For the enterprise network or large VoIP traffic route in
ITSP, it in no doubt that multiplexing is useful This is similar to VoFR environment
In case of flat traffic on IP-GWs network Effectiveness of multiplexing is considered
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Effectiveness of multiplexing? -flat traffic over IP-GW network-
1 2
3
N
N-1
Simplified Model Mesh Configuration Same traffic deviation between nodes
Internet
N 5 10 20 40 50
# of links 10 45 190 780 1225
calls/node 40 Total calls 100 200 400 800 1000ave mux# 10 4.4 2.1 1.0 0.8
calls/node 100Total calls 250 500 1000 2000 2500
ave mux# 25 11.1 5.2 2.6 2.0
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Effectiveness of multiplexing?(cont.) -flat traffic over IP-GW network-
10 20 30 40 Number of Nodes
n
umbe
r of
mul
tiple
1
1
0
20
simuntaneous calls/node : 40
simuntaneous calls/node :100
Multiplexing is useful for the IP-TEL NW
with several 10s of IP-GWs
Degree of Multiplexing
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Effectiveness of multiplexing?(cont.) -flat traffic over IP-GW network-
10 20 30 40 Number of Nodes
T
otal
P
acke
ts (
Nor
mal
ized
)0.
5
1.
0
w/o multiplexing
w/ multiplexingsimuntaneous calls/node : 40
w/ multiplexingsimuntaneous calls/node :100
packetsreduction
Packet Reduction
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Multiplex Sequence variable?
H1H121H232H33
3 2 1
3 2 1
3 2 1 Voice stream #3
Voice stream #2
Voice stream #1
t
Our implementation example shows “yes” shown below Variable multiplexing sequence(FIFO base) and variable
length Use of existing port for multiplexing new calls
Multiplexed stream
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Multiplexing method: Multiplexing Layer
IP
UDP
mux
RTP RTP RTPRTP
Voi
ce
Voi
ce
Voi
ce
Voi
ce
IP
UDP
New RTP profile
for muxV
oice
V
oice
Voi
ce
Voi
ce
RTP
(a) RTP Multiplexing (b) Multiplexing in RTP (c) New multiplexing method
IP
UDP
NewMultiplexing
method
Voi
ce
Voi
ce
Voi
ce
Voi
ce
RTP
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Multiplexing method: Multiplexing Format
IP-Header UDPHeader
RTP voice 1
20B 8B
……..RTPHeader
RTPHeadervoice voice
RTP voice n
12B+20B(G.723.1)
(a) RTP Multiplexing (Hitachi’s proposal)
IP-HeaderUDPHeader
20B 8B
……..RTPHeader Voice
1
Voice n
(b) Multiplexing in RTP (Lucent:Rosenberg’s new proposal)
12B
RTP-MUXHeader
2or4B/user
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Multiplexing method: Comparison RTP Multiplexing
While keeping RTP voice packet streams, and aggregate them into a multiplexed stream
“multiplex”profile exchange in H.245 call control required to be defined
RTP process modification: no Simple implementation way using current RTP voice packet
format Multiplexing in RTP
Define new payload type and format “multiplex” in RTP “multiplex”profile exchange: new payload type to be defined
within RTP RTP process modification: large Seems complex in implementation
New multiplexing method Define new protocol for multiplexing
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Multiplexing: Multiplexing Format proposal to IETF
Lucent: Rosenberg’s new proposal “An RTP Payload Format for User Multiplexing” http://www.ietf.org/internet-drafts/draft-ietf-avt-aggregation-00.t
xt
Hitachi’s proposal based on IP-GW implementation “An RTP Simple Transfer Method for Internet Telephony Gateway” http://www.ietf.org/internet-drafts/draft-tanigawa-rtp-multiplex-0
0.txt
July 16 -17 (c) 1998 All rights reserved, Hitachi, Ltd.
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VoIP Forum
Summary and Future Work
Examine additional delay and packet loss caused by multiplexing, which result in small influence to VoIP systems. Also, show the effectiveness of multiplexing.
Categorize multiplexing layer and protocol and introduce internet-draft proposals to IETF
More discussions needed for multiplexing format and protocol