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On Using Circuit-switched Networks
for File Transfers
Ph.D. Dissertation presented by
Xiuduan Fang
Department of Computer Science
University of Virginia
September 19, 2008
Outline
•
•
•
•
•
Overview
 Hypothesis
 Contributions & Publications
Motivation
Theoretical component:
 Design and evaluate algorithms to support file
transfers on circuit-switched networks
Experimental component:
 Implement and demonstrate architecture for
internetworking circuit-switched networks with the
Internet
Conclusions & Future work
2
Hypothesis
Circuit-switched networks, with dynamic callby-call bandwidth sharing and support for
heterogeneous-rate circuits, can be used
efficiently to support file transfers, and can be
evolved gradually into the existing Internet.
Dissertation organization
end-to-end circuits?
Yes
Theoretical component
Call-admission control (CAC):
No
Experimental component
Internetworking architecture
 rate allocation
 minimum file size
3
Key Contributions
•
File transfers on a hybrid architecture
 Constructed analytical models
 Provided insights on how to design admission control
 Proposed a novel heterogeneous rate-allocation
scheme to lower file-transfer delay
•
Internetworking architecture
 Designed and implemented a gateway to interconnect
circuit networks with the Internet
 Characterized the gateway performance
4
Publications
•
Ph.D. dissertation:
•
MS thesis:
 X. Fang and M. Veeraraghavan, On using circuit-switched
networks for file transfers,” accepted to IEEE Globecom, New
Orleans, LA, Nov. 2008.
 X. Fang, M. Veeraraghavan, M. E. McGinley, and R. W. Gisiger,
“An overlay approach for enabling access to dynamically
shared backbone GMPLS networks,” in Proc. of IEEE
ICCCN2007, Honolulu, Hawaii, Aug. 2007.
 X. Fang and M. Veeraraghavan, “On using a hybrid architecture
for file transfers,” Submitted to IEEE Transactions on Parallel
and Distributed Systems, 2008.
 M. Veeraraghavan, X. Fang, and X. Zheng, “On the suitability of
applications for GMPLS networks,” in Proc. of IEEE Globecom,
San Francisco, CA, Nov. 2006.
 X. Fang, X. Zheng, and M. Veeraraghavan, “Improving web
performance through new networking technologies,” IEEE
ICIW'06, Guadeloupe, French Caribbean, February 23-25, 2006.
5
Outline
•
Overview
 Hypothesis
 Contributions & Publications
Motivation
• Theoretical component:
•
•
 Design and evaluate algorithms to support file
transfers on circuit-switched networks
Experimental component:
 Implement and demonstrate architecture for
internetworking circuit-switched networks with the
Internet
Conclusions & Future work
6
Motivation
•
Why File Transfers on Circuit Networks?
 Packet switching is considered better than circuit
switching for file transfers
Pros: high throughput under light loads
 Cons:
– Unpredictable delays
– Proportional fairness but no temporal fairness

 eScience community is using high-speed
switched networks for very large file transfers
circuit-
Predictable service time (admission control)
 Temporal fairness: give deference to job seniority

7
Dissertation Organization
end-to-end circuits?
Yes
No
Theoretical component:
File transfers on
a hybrid architecture
Experimental component:
Interconnect circuit networks
with the Internet
Call blocking for circuit network?
No
Yes
Call blocking
circuit network
Call queueing
circuit network
 Implemented software
 Characterized performance
Published in ICCCN2007
rate allocation
homogeneous rate allocation
 Analytical model
 Designed a gateway
Homogeneous
Heterogeneous
Submitted to TPDS
 Analytical model
 Analytical model
Blocked calls rerouted
to the Internet path
 Simulation model
 Simulation model
 Fairness issue
Accepted by Globecom2008
For large files, waiting for high-speed circuit s is a better
option than being immediately rerouted to Internet path
Hybrid Architecture - Example
Internet2's new Dynamic Circuit (DC) network
Yellow nodes: Ciena CD-CI SONET switches
Blue nodes: Juniper T640 IP routers
Courtesy: Rick Summerhill
(2006)
9
Dissertation Organization
end-to-end circuits?
Yes
No
Theoretical component:
File transfers on
a hybrid architecture
Experimental component:
Interconnect circuit networks
with the Internet
Call blocking for circuit network?
No
Yes
Call blocking
circuit network
Call queueing
circuit network
 Implemented software
 Characterized performance
Published in ICCCN2007
rate allocation
homogeneous rate allocation
 Analytical model
 Designed a gateway
Homogeneous
Heterogeneous
Submitted to TPDS
 Analytical model
 Analytical model
Blocked calls rerouted
to the Internet path
 Simulation model
 Simulation model
 Fairness issue
Accepted by Globecom2008
For large files, waiting for high-speed circuits is a better
option than being immediately rerouted to Internet path
Call-blocking Circuit Network
•
Goal: design efficient connection-admission control
(CAC) algorithms
 Metrics: file-transfer delay and utilization
•
•
Block call if circuit is unavailable; reroute to Internet
Our focus:
 What is an appropriate minimum file size?
 Serve files sized x > minimum file size, Â, via the
circuit network
 What is an appropriate circuit rate, r, for a file transfer?
11
Analytical Model
Internet
N
¸0
x>Â
Y
1
…
routing decision
¸0
Link L
capacity C
n
Assumptions:
•
•
•
Circuit network
Single class
 homogeneous rate allocation
 m circuits; per-circuit rate, r=C/m
Call arrival process: Poisson with rate, ¸0 [Paxson95]
Call holding times: Pareto distribution [Crovella97]
[Paxson95] V. Paxson and S. Floyd, "Wide area traffic: the failure of Poisson modeling," Networking, IEEE/ACM Transactions on , vol.3, no.3, pp.226-244, Jun 1995
[Crovella97] M. E. Crovella and A. Bestavros, Self-Similarity in World Wide Web Traffic: Evidence and Possible Causes, IEEE/ACM Transactions on Networking, 5(6):835--846.
Key Insights

Combine M/G/m/m loss model & TCP delay model



Two criteria to select Â



Erlang-B formula: input the number of channels, m, & traffic load;
output: call blocking probability and utilization
TCP model: bottleneck link rate, round-trip time, packet loss rate
[Padhye98]
Delay-based (user-perspective): compare delay estimates
across two paths
Utilization (service provider-perspective): make circuit-setup
overhead a small fraction (e.g., 10%) of circuit file-transfer delay
Define a metric to quantify mean delay reduction
1
R = s-1 (E[Ttcp(x)]-E[Tcircuit(x)])¢fX(x)dx

Compute mopt (ropt = C/ mopt) & Âopt that maximize R
[Padhye98] J. Padhye, V. Firoiu, D. Towsley, and J. Kurose, “Modeling TCP throughput: A simple modeland its empirical validation,” in Proceedings of the ACM SIGCOMM, Aug. 1998, pp. 303–314.
Key Results
•
To maximize R, ropt should be much higher than effective
throughput on the Internet path
 e.g., Internet path: bottleneck link rate = 100 Mb/s,
RTT = 50 ms, packet loss rate = 1%
) effective throughput = 1.9 Mb/s
Circuit path: link capacity = 10 Gb/s, call-setup delay = 1 sec
) ropt = 63 Mb/s & Âopt = 75 MB
 If r = 2 Mb/s ) Â = 4.5 MB
) Files of size (4.5 MB, 75MB) will get lower delay on circuits
But, mean delay will increase; hence directed to Internet
•
Load sensitive: under low loads,
•
 Larger per-call circuit rate, ropt
 Larger ropt ) Larger minimum file size, Âopt
 Relax utilization criterion to decrease Âopt
RTT sensitive: Larger ropt & Âopt for short-RTT path
14
Dissertation Organization
end-to-end circuits?
Yes
No
Theoretical component:
File transfers on
a hybrid architecture
Experimental component:
Interconnect circuit networks
with the Internet
Call blocking for circuit networks?
No
Yes
Call blocking
circuit network
Call queueing
circuit network
homogeneous rate allocation
 Analytical model
Submitted to TPDS
Blocked calls sent to
the Internet path
 Designed a gateway
 Implemented software
 Characterized performance
Published in ICCCN2007
rate allocation
Homogeneous
Heterogeneous
 Analytical model
 Analytical model
 Simulation model
 Simulation model
 Fairness issue
Accepted by Globecom2008
For large files, waiting for high-speed circuits is a better
option than being immediately rerouted to Internet path
Homogeneous Rate Allocation
•
Key question: how much bandwidth should be allocated for
each file transfer so that the system performance is optimized
in terms of mean response time at a given effective utilization?
Metrics: mean response time
•
•
•
File size: boundedPareto distribution
Call arrival: Poisson
16
M/G/m queueing model
•
•
Goal: compute per-call circuit rate, ropt (i.e., C /mopt)
Input:
 A set of m = {1, 10, 100, 1000}
 Link capacity C = 10 Gb/s
) r = {10Gb/s, 1Gb/s, 100Mb/s, 10Mb/s}
 Call setup delay = 1 sec
 Bounded-Pareto parameters
) the first two moments of service time
 Traffic load 2 (0, 1)
•
Output:
 Effective utilization: call-setup delay overhead
 Mean waiting time
17
Numerical Results
Bandwidth allocation should be load sensitive
18
Heterogeneous Rate Allocation
•
Heterogeneous scheme: divide calls into classes based on file size &
allocate each class a different-rate circuit
A complete-partitioning system
19
Analytical model
•
•
•
Multiple separate M/G/m subsystems
 Basis for classifying calls: cutoff points, Â1,…, Ân-1?
 Bandwidth allocation per subsystem, C1, …, Cn?
 Ideal per-call circuit rate for each class, r1, …, rn?
To compute optimal operating point that minimizes mean
response time:
 Mathematica optimization package
 e.g., for a 2-class system
 Start with an initial value for Â1
 Determine C1, C2 & r1, r2
 Vary Â1 to study its impact
Fairness:
 Fairness ratio: ratio of mean slowdown of 2 classes
 Slowdown: ratio of waiting time to service requirement
20
 File-size distribution parameters:
Smallest file size: l = 1 MB
 Largest file size: u = 1 TB
 Cutoff point: Â = 1000 MB
 Homogeneous system is virtually
divided into 2 subsystems by Â
21
Fairness Ratio (small-file to large-file)
Homogeneous system
(at all utilization levels)
Heterogeneous system
•
A complete-partitioning heterogeneous scheme treats small
files more fairly when compared with a complete-sharing
22
homogeneous scheme
Simulation Study
• Single-link: simulation results are
•
consistent with analytical results
Multi-link: fairness study
 Short-path vs. long-path calls
 Work-conserving
scheme: unfair to long-path calls
 Proposed conditional-priority scheme: give priority
to long-path calls based on queue occupancy
 Small-file vs. large-file calls
 Complete-partitioning
heterogeneous scheme
23
Key Results
•
Complete-partitioning heterogeneous rate
allocation
 Large files allocated high-rate circuits
 Lowers mean response time
 Treats small files more fairly when compared with
complete-sharing
 Requires a network management system to monitor
traffic load & dynamically update partitions
•
Conditional priority scheme improves the fair
treatment between long-path and short-path
calls
24
Dissertation Organization
end-to-end circuits?
No
Yes
Theoretical component:
File transfers on
a hybrid architecture
Experimental component:
Interconnect circuit networks
with the Internet
Call blocking for circuit networks?
No
Yes
Call blocking
circuit network
Call queueing
circuit network
Submitted to TPDS
Blocked calls rerouted
to the Internet path
 Implemented software
 Characterized performance
Published in ICCCN2007
rate allocation
homogeneous rate allocation
 Analytical model
 Designed a gateway
Homogeneous
Heterogeneous
 Analytical model
 Analytical model
 Simulation model
 Simulation model
 Fairness issue
Accepted by Globecom2008
For large files, waiting for high-speed circuit s is a better
option than being immediately rerouted to Internet path
Experimental Component
•
Motivation:
 It is expensive to deploy a new networking technology on an
end-to-end basis
 As link speeds increase, high-capacity circuit switches are
cheaper than packet switches
 Circuit-switched (CS) networks operated in shared mode )
admission control (AC) phase
 Connectionless (CL) networks have no admission control
phase
 So internetworking CL + shared CS is a challenge
•
Our solution: gateway that implements all sub-layers of the
network layer with data-plane and control-plane (AC)
•
Metrics: reliable file transfer, circuit utilization, forwarding rate
26
Related Work
•
State-of-the-art: IP routers
•
 Original purpose: interconnect connectionless networks [Cerf74,
RFC791, Clark88]
 Connection-oriented networks when used in the Internet are
used only in leased-line mode
Proposed but not deployed:
 IP-over-ATM internetworking: Ipsilon's IP switching
 Routers have to "guess" which flows are long-lived
 TCP switching: IP switching with protocol classifier
[Cerf74] V. G. Cerf and R. E. Kahn, “A protocol for packet network intercommunication,” IEEE Transactions on Communications, vol. 22, no. 5, pp. 637–648, May 1974.
[Clark88] D. D. Clark, “The design philosophy of the DARPA Internet protocols,” in SIGCOMM. Stanford, CA: ACM, Aug. 1988, pp. 106–114.
27
Internetworking Architecture
R
Web client
R
S
R
R
CAG
R
CAG
CAG
R
regional
network
Circuit
subnetwork
S Ethernet switch
S
R
R
R
Connectionless
R IP router
Web server
R
R
S
R
enterprise
network
IP-router core
subnetwork
regional
network
S
enterprise
network
Connectionless
circuit/VC switch
CAG Circuit-aware application gateway
28
Internetworking Architecture
R
IP-router core
subnetwork
Web client
R
S
R IP router
R
R
R
S
R
enterprise
network
Web server
R
CAG
R
CAG
CAG
R
regional
network
S Ethernet switch
HTTP/TCP/connectionless IP
R
R
R
Circuit/
subnetwork
circuit/VC switch
S
regional
network
S
enterprise
network
CAG Circuit-aware application gateway
HTTP/CTCP/circuit
29
Gateway Design
•
Start with an open-source Web proxy software
package called Squid
•
Data-plane:
 Base functionality provided by Squid
 Integrated Circut-TCP (removes Slow Start, receive-side
autotuning)
•
Control-plane: Integrated RSVP-TE signaling client
module into Squid to initiate circuit setup/release
30
Gateway Design contd.
•
•
•
•
•
•
•
•
Unpredictable rate across connectionless (CL) segments
But fixed-rate across circuit-switched (CS) segments
What if these are mismatched?
Need buffering within gateways
Buffers are finite: so possibility of losses?
Squid implementation: back-pressure mechanism;
 Data not read from incoming TCP buffer if Squid buffer
(controlled by read_ahead_gap) is full
 Latter is full if outgoing TCP buffer is full
Leads to circuit utilization problems
Answer: main memory or disk buffering in gateways +
multiplexing on circuits
31
Experimental Hypothesis
A modified version of Squid software can be used
as a gateway to interconnect circuit-switched
networks and connectionless packet-switched
networks for reliable file transfers, and can support
an effective throughput of 460 Mb/s when executed
on a Linux 2.6.20 host with a 2.8GHz Xeon
processor and 1 GB memory.
32
Experimental setup to test
if there is buffer overflow
•
•
•
•
NIC speeds: CHEETAH NIC (NIC2) = GbE, Internet NIC (NIC1) ¸ 100 Mb/s
Circuit (zelda1 $ zelda4) rate=155Mb/s, link (zelda4 $ zelda5) rate=1Gb/s
Control link rate on zelda1 ! zelda2 path to mismatch sending and
receiving rates
The parameter read_ahead_gap controls CAG’s application buffer for each
flow, read_ahead_gap = 16 KB (default value)
33
CAG zelda1’s forwarding rate
CAG zelda1’s CPU and memory usage
•
Key results:
 No packet loss in buffers within
CAGs due to a back-pressure
mechanism
 Drawback: low circuit utilization
e.g., only 1/155 < 1% for 1 Mb/s
bottleneck link rate
CAG zelda1’s receive window size for
zelda1 $ zelda4 CTCP connection
34
Improving Circuit Utilization
•
Configured read_ahead_gap:
 e.g., when read_ahead_gap (for CAG zelda1) = 1 GB, circuit
utilization = 90% for a 1-GB file transfer
 Problem: unscalable because Squid only uses main memory for
buffering in-transit data
•
Disk buffering: used two instances of Squid on a CAG
35
Other Experiments & Analysis
•
Measured maximum forwarding rate
 Stress test by using long flows: 460 ± 4.75 Mb/s
•
Measured user-perceived throughput
 Throughput improvement when circuits replace
congested Internet paths.
•
Related the internetworking architecture with the
TCP/IP & OSI reference models
 Fits into the OSI model
36
Conclusions
•
File transfers on circuit-switched (CS) networks
 Advantage relative to packet switching: predictable service time
•
Packet switching (PS) better for small file transfers
 Call setup delay >> Transfer time (link rates ↑, transfer time ↓)
 Predictability not a concern when absolute delays are low
•
Hence hybrid architecture: PS for small; CS for large
Internet path
Considered in
Not
Circuit
metrics routing decision
considered
network operation
Call blocking
√
X
Call queueing
X
√
 Call admission control algorithms designed to be fair across
small-file, large-file & across short-path, long-path
37
Conclusions contd.
•
Designed a gateway called CAG to interconnect
connectionless networks with circuit networks
 CAG implements all sub-layers of the network layer with
data-plane and control-plane (admission control)
 CAG supports reliable file transfers
 File transfers need high-speed links on whole path
 Gradually evolving circuit-switched networks for access
(current bottleneck) will lead to improved performance
38
Future Work
•
More sophisticated bandwidth-sharing schemes
 Currently studied a complete partitioning scheme
 To avoid sensitivity to network management system
performance as is the case with partitioning
•
Hardware-based implementation of CAG with the
support of disk buffering for in-transit data
 Current software implementation could slow down
effective transmission rates
39
Questions from Form G111
Thank you!
Questions?
41
Questions from Form G111 -
Defining the problem
•
Has the student stated the problem clearly, provided
its motivation, and the requirements for a solution?
•
In the context of new optical circuit-switched
technologies and new application requirements, how
do we support file transfers efficiently on a
dynamically shared circuit-switched network and
how can we interconnect a circuit network with a
connectionless network?
42
Questions from Form G111 -
Analysis of previous and related work
•
Theoretical component: file transfers on circuit networks
 Packet switching is considered better
 But circuit switching provides rate guarantees
 Very large file transfers on optical connection-oriented testbeds



e.g.: ESnet4, NSF DRAGON, CA*net4, UKLight, JGN2, etc.
Focus: implementation & inter-domain usage
Our work: how much bandwidth to allocate per file transfer
 File transfers have not been considered on other circuit/virtual-circuit
networks

•
e.g.: telephone networks, ATM
Experimental component: interconnect circuit networks with
connectionless networks
 State-of-the-art: IP routers


Original purpose: interconnect connectionless networks
Used leased line modes to include circuit networks
 Proposed but not deployed: IP switching & TCP switching
 Our work: gateway that handles service-type mismatch between
connectionless and circuit networks
43
Questions from Form G111 -
Success criteria
•
Has the student adequately defined the measure(s) of success to be
used to evaluate the work? Is there a well defined metric with a goal?
Does the metric adequately represent the desired success criteria?
•
Success criteria
 Theoretical work: use a hybrid architecture for file transfers

Call blocking circuit network: optimal design parameters to maximize mean
delay reduction
 Call queueing circuit network: optimal design parameters to minimize mean
response time at a given effective utilization
 Experimental work: designed an internetworking gateway called CAG



•
CAG supports reliable file transfers
Improved circuit utilization
Measured maximum forwarding rate of CAG
Metrics
 Theoretical work: file-transfer delay, utilization, mean delay reduction,
fairness ratio
 Experimental work: reliable file transfer, circuit utilization, forwarding rate,
user-perceived throughput
44
Questions from Form G111 -
Solution
•
Is the approach taken well executed? Does it appear to be correct?
Is the work technically challenging? Does the student utilize
appropriate professional standards?
•
A combination of analytical, simulation, and experimental methods
 Call blocking circuit network for file transfers
 Analytical model
 Call queueing circuit network for file transfers
 Analytical model
 Simulation model
 An internetworking gateway
 Software implementation
 Experimentation and measurements
 Architecture positioning
45
Questions from Form G111 -
Innovation and risk
•
To what extent is the work innovative? Has the student taken a risk
in applying the chosen approach?
•
Bandwidth sharing problem on using circuit networks for file
transfers has not been studied before
•
The problem of internetworking connectionless networks and
dynamically shared circuit networks has not been addressed widely
(only one previous solution – from the 90s which proved unviable)
46
Questions from Form G111 -
Broader implications
•
Has the student considered the broader implications of
the work? Broader implication may include social,
economic, political, technical, ethical, business, etc.
•
Enable the deployment of high-speed circuit networks at
low costs (sharing) to provide predictable-delay services
 New applications can be created with this type of service
•
Integrated with Internet
 Avoids need for desert-start deployment
47
Background –
High-Speed Circuit-Switching
•
Data-plane technologies
 Switching: Time Division Multiplexing (TDM) &
Wavelength Division Multiplexing (WDM)
 Mapping: to carry Ethernet frames via SONET signals or
WDM lightpaths
•
Control plane: Generalized MultiProtocol Label
Switched (GMPLS)
 Three components: signaling, routing, & management
 Bandwidth sharing mode: immediate-request (IR)
•
Equipment examples:
 SONET switches: Sycamore SN16000
 WDM switches: Adva/Movaz RayExpress OADM
48
Layers in OSI reference model
AL: Application Layer
TL: Transport Layer
DLL or L: Data-Link Layer
PHY or P: Physical Layer
Sublayers of network layer (NL)
• SNICF: Subnetwork Independent Convergence Function
• SNDCF: Subnetwork Dependent Convergence Function
• SNACF: Subnetwork Access Function
• SNSF: Subnetwork Switching Function
[ITU X.200] http://www.itu.int/rec/T-REC-X.200-199407-I/en
[Callon83] R. E. Callon, "Internetwork protocol,“ Proc of the IEEE, vol. 71, no. 12, pp. 1388-1393, Dec. 1983
Layers in the Internetworking
Architecture
This internetworking architecture fits into OSI reference model
50
Analytical Model: Homogeneous Rate Allocation
•
File-size distribution: bounded-pareto, BP(®, l, u),
®: shape, l: minimum file size, u: largest file size
•
Service time:
•
Per-server traffic intensity:
•
Effective utilization:
•
Mean waiting time:
•
Mean response time:
Analytical Model: Heterogeneous Rate Allocation
•
Each subsystem:
 File-size distribution: bounded-pareto, BP(®, Âi-1, Âi),
®: shape, Âi-1 : minimum file size, Âi : largest file size
E[Y j ] =  pi ¢ E[Yij]
 Call arrival rate:
 Capacity:
•
Whole system:
 Effective utilization:
 Mean response time:
Simulation Results: Multiple-link
53
Model Validation & Verification
•
Model validation
“Three aspects of model validation
 Assumptions
 Input parameter values and distributions
 Output values and conclusions” [Jain91]
 Our models are for an initial design
to support file transfers on circuit networks
 No real-world measurements
 Model validation technique – peer/expert reviews
 Real system measurements “available”
for input parameters
 E.g., real-system measurements for file transfer
– Poisson call arrival process
– Pareto distribution
•
Model verification
“Three validation techniques
 Expert intuition
 Real system measurements
 Theoretical results” [Jain91]
 Compare analytical model results with simulation model results
[Jain91] R. Jain, The Art of Computer Systems Performance Analysis: Techniques for Experimental Design, Measurement, Simulation, and Modeling, New York, Wiley-Interscience, 1991.
54
Related Work –
File Transfers on Other Testbeds
•
•
Other testbeds: Large file transfers  high per-circuit
rate, long holding time  Coarse-Grained Sharing
(CGS)
Our interest: Fine-Grained Sharing (FGS) for all files
Leased Line
CGS
FGS
coarse
TCP/IP
fine
Different bandwidth sharing modes
55
Circuit-switched networks:
Signaling for call setup
Connection setup (Dest: III-B;
BW: OC1; Timeslot: a, 1)
II
a
b
Host
I-A
a
III
I
c
b
d
c
Routing
table
Dest.
Next hop
III-*
IV
a
IV
d
Host
III-B
b
c
V
Connection setup actions at each switch on the path:
1.
Parse message to extract parameter values
2.
Lookup routing table for next hop to reach destination
3.
Read and update CAC (Connection Admission Control)
table
4.
Select timeslots on output port
5.
Configure switch fabric: write entry into timeslot
mapping table
6.
Construct setup message to send to next hop
56
Connection-Admission Control (CAC)
Network
Management System
configures Â
Y
1
2
N-1
N
Receive a file-transfer
request with size x
 & rx
¸
CAC
x>Â
N
Simple
sum
Â: crossover file size
rx: allocated bandwidth
Switch model
Y
allocate a circuit
with rate rx
reject
Simple sum:
rx < available bandwidth
N
accept
reject
The procedure of CAC
57
Design and Implementation
•
How does a CAG select the “best” parent?
 Static configuration based on geographic location of
Web servers using ARIN WHOIS database
•
How does a user configure the Web client to use
the Web proxy server?
 Configuring for every request is not user-friendly
 Instead, use Proxy Auto-Configuration (PAC)
58
File Transfers on
Other Circuit/VC Networks
•

Has ATM implemented file transfers with a guaranteed
service?  No.
Service classes on the ATM layer
 Hard QoS for multimedia applications

CBR: voice & VBR: audio
No QoS at the ATM level for all other data traffic
 ABR & UBR
File transfers are served by UBR
 No guaranteed bandwidth allocation
 Loss recovered with ARQ in TCP
 No effort to maintain flow rate to match VC rate


59
Analytical Model (cont.)

M/G/m/m loss model

Erlang-B: compute call blocking probability, Pb, and utilization, Ub,
given the number of channels, m, and traffic load, ½
0
1
N
…
RD

Link L, capacity C
RD: routing decision
A switch model for file transfers

The computation of ½:
¸: aggregate call arrival rate offered to the switch
1/¹: mean call holding time
60
The Derivation of
Offered Traffic Load, ½
File size: Pareto distribution
®: shape, k: scale
Circuit file-transfer delay
Mean call holding time
Tprop: propagation delay
Serve files with
size x > Â
Original call
arrival rate, N¢¸0
Mean file size
Aggregate offered call arrival rate
Offered traffic load
C/m: per-circuit rate
61
The Selection of
Crossover File Size, Â

Delay-based, Âd: compare two delay values
where
Pb: call blocking probability

Utilization-based, Âu: the mean call-setup delay, E[Tsetup], is
a small fraction of circuit file-transfer delay, Ttransfer(x)
e.g., ¯=10

Choose
62
Numerical Results - Input Parameters

File size distribution: shape, ®=1.0009, scale,
k=1000bytes

Circuit:






Link capacity C=10Gbps
Original call arrival rate, N¢¸0=1100calls/second
Mean call setup delay, E[Tsetup]=1second
Round trip time, RTT=50ms
Utilization factor, ¯=10
Internet path



Bottleneck link rate, r=100Mbps
Packet loss rate, Ploss=1%
Round trip time, RTT=50ms
63
Delayed-based crossover file size
Utilization-based crossover file size
Numerical Results:
Impact of Per-circuit Rate on Â
Link capacity expressed in channels
High per-circuit rate
Low per-circuit rate
64
m=1000
m=100
Delayed-based crossover file size
Utilization-based crossover file size
Numerical Results:
Impact of Per-circuit Rate on Â
For m=10, 100, and 1000 (i.e, per-circuit rate is 1Gb/s, 100Mb/s, and 10Mb/s)
Âu is the limiting factor  Simplifies the computation of Â
65
File transfer delay over circuits or the Internet
Numerical Results: Impact of
Per-circuit Rate on File-transfer Delay
m=10, 100, and 1000 $
per-circuit rate is 1Gb/s
100Mb/s, & 10Mb/s
(11.9MB)
(118.9MB)
(1.2GB)
66
Numerical Results: Impact of
Per-circuit Rate on Mean Delay Reduction
67
Design and Implementation
•
Gateway:
Receive a Web request
 Started with an opensource Web proxy
Y
N
software package called
Cache miss
Squid
 Integrated RSVP-TE
Circuit to
N
Y
signaling client module
Serve the
parent
into Squid to initiate circuit
request
set up/release
 Integrated Circut-TCP
(removes Slow Start,
Fork a process to
Serve the
receive-side autotuning)
attempt a circuit setup;
request via
 Added monitoring module the circuit
Meanwhile, serve the
to watch circuit usage.
request via the IPInitiate circuit release if
router core subnetwork
idle for time >T
68
Experiments to Measure
User-perceived Response Time
• Two sets
 Controllable experiments by loading specificsize files on a Web server
 Operational Web sites
• For each set, two tests
 Direct without proxy
 CHEETAH proxy: via CAGs but without
caching
69
Experimental Results – 1st Set
Web client:
unc-planetlab1
Chapel Hill, NC
Internet
Web server:
zelda2
NIC1
NIC2
SN16000
zelda1
NIC1
CHEETAH
CAG
NIC2
SN16000
circuit
Atlanta, GA
wuneng
Raleigh, NC
CAG
CHEETAH proxy
direct
unc-planetlab1
zelda2
unc-planetlab1
wuneng
wuneng zelda1
(circuit)
zelda1zelda2
10.77 ms
1.27 ms
8.87 ms
0.23 ms
File size
Test(Mb/s)
100 KB
1 MB
10 MB
100 MB
Direct
10.70± 0.65
15.08± 0.55
17.25± 0.52
16.71± 0.66
CHEETAH proxy
13.61± 0.76
46.40± 1.70
64.64± 3.21
58.59± 2.30
70
Experimental Results –
nd
2
Web server
Web client
Ballstein.cs.virginia.edu
wuneng
Web server parameters
name
Set
CHEETAH
zelda1
RTT (ms)
via the
Internet
Bottleneck
local RTT
(ms)
file size
(MB)
Latencies (s)
direct
CHEETAH
Proxy
location
kernel.org
Carrollton,
TX
86
61.6
48
70
33
sourceforge.net
Atlanta, GA
32
14.6
113
520
140
71
Background –
High-Speed Circuit-Switched Networks




US: DOE’s UltraScience net, CHEETAH, Internet2 Dynamic Circuit network
Europe: UKLight (UK), SURFnet (Netherland), VIOLA (Germany), MUPBED
Canada: CA*net 4
Japan: JGN
Oak Ridge, TN
Raleigh, NC
SN16000
GbE/
OC192 Control
10GbE
card Card
card
To Cray X1
H zelda4
H zelda5
SN16000
GbE/
OC192 Control
10GbE
card Card
card
H wukong
Atlanta, GA
OC-192
OC-192
SN16000
GbE/
OC192 Control
10GbE
card Card
card
H zelda1
H zelda2
H zelda3
CHEETAH: Circuit-switched High-speed
End-to-End Transport ArcHitecture
SN16000: circuit switch
72
Numerical Results for
Fixed Per-call Circuit Rates
Under high loads (U > 73%), heterogeneous scheme
lowers mean waiting time
 By partitioning, small files do not need to wait for large files to
complete ) small files are treated more fairly
73