Tài liệu Supporting Configurable Congestion Control in Data Transport Services ppt

1 ::
23
udt.sourceforge.net
Supporting Configurable Congestion Control in
Data Transport Services
Yunhong Gu and Robert L. Grossman
Laboratory for Advanced Computing
National Center for Data Mining
University of Illinois at Chicago
November 16, 2005
udt.sourceforge.net
2 ::
23
udt.sourceforge.net
Outline
OVERVIEW
DESIGN OF UDT/CCC
PERFORMANCE EVALUATION
CONCLUSIONS AND FUTURE WORK
3 ::
23
udt.sourceforge.net
>> OVERVIEW
DESIGN OF UDT/CCC
PERFORMANCE EVALUATION
CONCLUSIONS AND FUTURE WORK
4 ::
23
udt.sourceforge.net
From UDT to Composable UDT


UDT (UDP-based Data Transfer Protocol)

New application level protocol: add reliability and congestion control to
UDP

New congestion control algorithm designed for high performance data
transfer over high-speed wide area networks

Open source:

Composable UDT

An expansion to UDT with ability to allow users to configure the UDT
library: congestion control, data reliability, etc.

Compile time option: no performance drop for the original UDT
5 ::
23
udt.sourceforge.net
UDT with Configurable Congestion Control (CCC)

CCC support is the first step of
Composable UDT

UDT/CCC allows user to implement or assign
a specific congestion control algorithm to
a UDT connection

Per connection control


Dynamically configurable
6 ::
23
udt.sourceforge.net
Motivations

Easy implementation and deployment of new
control algorithms

Easy evaluation of new control algorithms

Application awareness support and dynamic
configuration
7 ::
23
udt.sourceforge.net
>> DESIGN OF UDT/CCC
PERFORMANCE EVALUATION
CONCLUSIONS AND FUTURE WORK
OVERVIEW
8 ::
23
udt.sourceforge.net
UDT with Configurable Congestion Control
UDP
Socket API
Applications
UDT
UDT Socket
CC

CC Callbacks
Memory Copy
Bypass
9 ::
23
udt.sourceforge.net
Methodologies

Packet sending control

Window-based, rate-based, and hybrid

Control event handling

onACK, onLoss, onTimeout, onPktSent, onPktRecved, etc.

Protocol parameters access

RTT, loss rate, RTO, etc.

Packet extension

User-defined control packets
10
::
23
udt.sourceforge.net
Supported Protocols

Reliable UDP-based Protocols


Standard TCP (TCP NewReno)

Loss-based TCP Variants

Delay-based TCP Variants

Group-based Protocols

And more…
11
::
23
udt.sourceforge.net
Examples: Reliable UDP Blast
class CUDPBlast: public CCC
{
public:
CUDPBlast() {m_dCWndSize = 83333.0;}
public:
void setRate(int mbps)
{
m_dPktSndPeriod = (m_iSMSS * 8.0) / mbps;
}
protected:
static const int m_iSMSS = 1500;
};
12
::
23

udt.sourceforge.net
Examples: Reliable UDP Blast
UDT::setsockopt(usock, 0, UDT_CC,
new CCCFactory<CUDPBlast>,
sizeof(CCCFactory<CUDPBlast>));
CUDPBlast* cchandle = NULL;
int size = sizeof(CUDPBlast);
UDT::getsockopt(usock, 0, UDT_CC, &cchandle,
&size);
if (NULL != cchandle)
cchandle->setRate(500);

cchandle->setRate(1000);
13
::
23
udt.sourceforge.net
Examples: TCP NewReno
virtual void onACK(const int& ack)
{
if (three duplicate ACK detected) {
// ssthresh = max{flight_size / 2, 3}
// cwnd = ssthresh + 3 * SMSS
} else if (further duplicate ACK detected) {
// cwnd = cwnd + SMSS
} else if (end fast recovery) {
// cwnd = ssthresh
} else {
// cwnd = cwnd + 1/cwnd
}

}
14
::
23
udt.sourceforge.net
>> PERFORMANCE EVALUATION
CONCLUSIONS AND FUTURE WORK
OVERVIEW
DESIGN OF UDT/CCC
15
::
23
udt.sourceforge.net
Evaluation

Simplicity

Can it be easily used?

Expressiveness

Can it be used to implement most control protocols?

Similarity

Can Composable UDT based implementations reproduce the
performance of their native implementations?

Overhead


Will the overhead added by Composable UDT be too large?
16
::
23
udt.sourceforge.net
Simplicity & Expressiveness

Eight event handlers, four protocol
control functions, and one performance
monitoring function.

Support a large variety of protocols

Reliable UDT blast

TCP and its variants (both loss and delay based)

Group transport protocols
17
::
23
udt.sourceforge.net
Simplicity & Expressiveness
CCC
Base Congestion
Control Class
CTCP
TCP NewReno
CGTP
Group Transport

Protocol
CUDPBlast
Reliable UDP
Blast
CFAST
FAST TCP
CVegas
TCP Vegas
CScalable
Scalable TCP
CHS
HighSpeed TCP
CBiC
BiC TCP
CWestwood
TCP Westwood
28
73 / +132-6 11 / +192-29 8 / +27-1 11 / +192-29 27 / +145-2
37 / +351-2
18
::
23
udt.sourceforge.net
Similarity and Overhead

CTCP vs. Linux TCP

Aggregate throughput

Jain’s fairness index


Stability index (standard deviation)
Flow
#
Throughput Fairness Stability
TCP CTCP TCP CTCP TCP CTCP
1 112 122 1 1 0.517 0.415
2 191 208 0.997 0.999 0.476 0.426
4 322 323 0.949 0.999 0.484 0.492
8 378 422 0.971 0.999 0.633 0.550
16 672 642 0.958 0.985 0.502 0.482
32 877 799 0.988 0.997 0.491 0.470
64 921 716 0.994 0.996 0.569 0.529
19
::
23
udt.sourceforge.net
CPU Overhead vs. ACK Frequencies

CPU usage

Sender: CTCP uses about 100% more times of CPU as Linux TCP

Receiver: CTCP uses about 20% more CPU than Linux TCP

Source of overheads

Additional memory copy and context switch

ACK Frequencies is one of the major factors

Flow
#
ACK Intervals
2 4 8 16 32 64 128
1 3.28 3.15 3.20 3.43 2.57 2.59 2.07
2 3.91 3.77 3.95 3.59 3.52 3.35 3.51
4 4.32 4.36 1.45 3.08 3.54 3.44 3.27
8 4.05 4.87 4.32 3.84 3.91 3.63 3.63
16 4.59 5.07 5.60 4.41 4.41 4.17 3.12
32 5.41 5.31 5.27 4.99 5.15 4.53 4.01
64 6.63 6.58 6.15 5.89 5.35 5.08 4.51
20
::
23
udt.sourceforge.net
>> CONCLUSIONS AND FUTURE WORK
OVERVIEW
DESIGN OF UDT/CCC
PERFORMANCE EVALUATION
21
::
23
udt.sourceforge.net
Conclusions

We expanded our UDT protocol with support
for configurable congestion control

Easy implementation and deployment of new control algorithms


Easy evaluation of new control algorithms

Application awareness support and dynamic configuration

Pros

Simplicity and expressiveness

Easily deployable

Cons

CPU overhead
22
::
23
udt.sourceforge.net
Future Work

Keep improving

More built-in congestion control package

More configuration abilities (e.g., data
reliability and timeliness)
23
::
23
udt.sourceforge.net
The End

Thank You!
For More Information
Please visit:
SC|05 Exhibition Booth 2430
Or online at