apohn: subnetwork layering to improve tcp performance over heterogeneous paths april 4, 2006 dzmitry...
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APOHN:Subnetwork Layering to Improve TCP
Performance over Heterogeneous Paths
April 4, 2006
Dzmitry Kliazovich,
Fabrizio Granelli,
University of Trento, Italy
Giovanni Pau,Mario Gerla
University of California, Los Angeles
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Presentation Outline TCP/IP in Heterogeneous Networks
APOHN Architecture Techniques, Protocol, and Security
Performance Evaluation In Satellite + Wireless LAN Network
Conclusions and Future Potential
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Background TCP/IP protocol suite Nowadays Networks
(Heterogeneous)
Designed in late 70s (ARPANET) Strong Hierarchical structure Static Routing Stable Connectivity Small Propagation Delays Low Error Rates (BER: 10-8 – 10-6)
Wireless, Satellite links Terminal Mobility Limited Bandwidth Large Propagation Delays Signal Fading High Error Rates (10-3 – 10-1)
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
TCP/IP Improvements
Modify TCP bringing desired behavior Examples: TCP Westwood, TCP-DOOR, etc. Drawbacks: Difficulty to maintain E2E semantics, requires modification
of standardized and widely implemented TCP/IP stack
Transparent Adaptation
TCP Modification
Hide from TCP undesirable physical characteristics Examples: ARQ and FEC at the link layer Drawback: Not all the characteristics can be compensated in
transparent way
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
TCP/IP Semantics
S end er R ec eiverR o uter
N etw o rk
Physical Physical
Link Link
Network (IP) Network (IP)
TCP TCP
S end erR ec eiver
ConnectNeighbor Nodes
ConnectNetwork Nodes
Connection Service forApplications
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
TCP/IP Semantics Heterogeneous Network?
S ubne t 1 S ubne t 2 S ubne t 3
S end er
R o uter R o uterR ec eiver
Physical Physical
Link Link
Network (IP) Network (IP)
TCP TCP
Subnetwork Subnetwork
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
APOHN Architecture
TC P , U D P E n d - to - en d
S ubne t 1 S ubne t 2 S ubne t 3
A pplic a tion
IP
L ink SB 1
P H Y SB 1
SB P SB 1
L ink SB 1
P H Y SB 1
SB P SB 1
L ink SB 2
P H Y SB 2
SB P SB 2
IP
L ink SB 2
P H Y SB 2
SB P SB 2
L ink SB 3
P H Y SB 3
SB P SB 3
IP
TC P , U D P
A pplic a tion
IP
L ink SB 3
P H Y SB 3
C P SB 3
Applic at io n
Trans po r t
N e two rk
Subne two rk
L ink
P hys ic al
Ope
ratin
g Sy
stem
TC
P/I
PIn
terf
ace
card
or d
river
S end er
R o uter R o uterR ec eiver
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
APOHN Architecture Optimize Subnetwork Communications
Subnetwork Protocols (SBP)
Split-Connection at Subnetwork Layer
Preserve End-to-end Transport Layer
No Changes for TCP/IP OS Implementation
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Protocol Booster
Buffer TCP packets
Control TCP with Receiver Advertise windows (rwnd)
E2E Reliability: keep a packet in buffer until it’s E2E acknowledged
T C P A C Kge ne rato r
(o ne pe r p acke t)C lass if ie r
S ubne two rk Laye r
Ne two rk Laye r (IP )
Pro to co lB o o s t er
T ranspo rt Laye r (T C P )
Protocol Booster – Transparent interface between TCP and Subnetwork layers
D. Feldmeier at el., “Protocol boosters,” IEEE JSAC, vol. 16, no. 3, pp. 437 – 444, 1998.
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Protocol Booster Implemented at Sender Node
Protocol Booster completely disables TCP flow control mechanism without direct modifications on Transport layer
TCP becomes a controlled source of packet data
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Subnetwork Flow Multiplexing Rate-based or Window-based flow control at Subnetwork layer Results in TCP flow speed up: no need to probe the capacity with
Additive Increase Multiplicative Decrease (AIMD)
S ubne t
. . .
T C P /UD P f lo w
T C P /UD P f lo w
T C P /UD P f lo w
T C P /UD P f lo w
T C P /UD P f lo w
T C P /UD P f lo w
. . .
S ub netw o rk P ro to c o l(S B P )
Trans po r t Subne two rk Subne two rk T ra ns port
Network Utilization Increase
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Related Works Delay-Tolerant Network (DTN)
Overlay network Adds Bundle layer above TCP E-mail style communications
Drawbacks Modifies TCP/IP Requires dedicated (overlay) nodes Router nodes process whole protocol stack Can not handle delay sensitive traffic
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Related Works Performance Enhancement Proxy (PEP)
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Related Works Performance Enhancement Proxy (PEP)
Designed for links or Subnetworks where TCP/IP performs poor Typically Satellite links
Commonly Split-Connection approach End-to-end connection is split into two or more connections Use Optimized (non-TCP/IP) Protocol over a Problematic
Link
Drawbacks End-to-end Semantics not prevented Large Processing + Buffer Overhead Inability to Handle IPSec
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Secure Communications Split-Connection on Transport Layer (like PEP) can not
support IPSec Multilayer IP Security (by Zhang at el.) as an adaptation
of IPSec for split-connection PEPs Divide network in the number of Zones (Subnetworks) Encrypt for every zone (not End-to-end)
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Secure Communications APOHN IPSec Support
End-to-end IPSec (RFC 2401) Additional Subnetwork Security (Optional)
S ubne t 1 S ubne t 2
S end er
R o uterR ec eiver
TC P hdr
SB P hrd
TC Pdata
IP hdr
IP SE C hdr
I P s ecen c r y p t
TC P hdr
SB P hrd
TC Pdata
IP hdr
IP SE C hdr
TC P hdr
SB P hrd
TC Pdata
IP hdr
IP SE C hdr
TC P hdr
SB P hrd
TC Pdata
IP hdr
I P s ecd ec r y p t
TC P hdr
SB P hrd
TC Pdata
IP hdr
S u b n eten c r y p t
S u b n etd ec r ip t
S u b n eten c r y p t
S u b n etd ec r y p t
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation Simulated network: Satellite + Wireless LAN
Distributed Communications with no fixed infrastructure Disaster Recovery, Military Applications
S ate ll i te /W L A NR o u ter
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation APOHN Subnetwork Protocols
Satellite Transport Protocol (STP) over Satellite Link LLE-TCP (ACK suppression) over WLAN
T C P N ew renoS A C K
T C P N ew renoS A C K
S T P S T P
IP IP
LLE -T C P LLE-T C P
S atelliteLL /P H Y
S atelliteLL /P H Y
802.11LL /P H Y
802.11LL /P H Y
R ate C o ntro l A C K S up p res s io n
End -to -end
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation Ns-2 Simulation Scenario
Satellite Link: 20 Mb/s, 300 ms downstream; 6 Mb/s, 300 ms upstream
Wireless LAN Link: IEEE 802.11b (PHY – 11 Mb/s)
T C P N e wR e noAge nt
T C P S A C KS ink
S T P A gent S T P S ink LLE -T C PA gent
LLE -T C PS ink
802.11b S haredM ed ium
(P H Y : 11 M b /s )
End -to -end
B o o s ter A gent T C P S ink(o ne p er p ac ket)
S T P A gentS T P S ink
d o w nlink: 20 M b /s , 300 m s
up link: 6 M b /s , 300 m s T C P S A C KS ink
Legend :
T C P d a ta T C P a c k no w le d ge m e nts
S en d er R eceiver
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation Single-Flow Scenario
TCP Reno SACK triggers multiple timeouts SaTPEP is limited by WLAN bottleneck
0 200 400 600 800 1000 1200 1400 1600 1800 20000
1
2
3
4
5
6
7
time (s)
Go
od
pu
t (M
b/s
)
NewReno SACKSaTPEP
APOHN
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation Congestion Window Evolution
0 500 1000 1500 20000
50
100
150
200
250
300
350
400
time (s)
Co
ng
est
ion
Win
do
w (
pa
cke
ts)
TCP Newreno SACKConnection Capacity
Loss Detectedwith DupACKs
Loss Not Detected,Timeout
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation Bottleneck Buffer
0 500 1000 1500 20000
5
10
15
20
25
30
35
40
45
50
time (s)
Bu
ffer
size
(p
ack
ets
)
APOHNTCP/IP
Multiple OverflowDrops
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation Multi-Flow Scenario
0 5 10 15 200
1
2
3
4
5
6
7
Number of Flows
Ave
rag
e C
um
mu
lativ
e G
oo
dp
ut (
Mb
/s)
APOHNSaTPEPTCP/IP
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Performance Evaluation Cumulative Throughput
0 500 1000 1500 20000
2
4
6
8
10
12x 10
5
time (s)
Ack
no
wle
dg
ed
pa
cke
ts
APOHNSaTPEPTCP/IP
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Conclusions and Future Work Need for TCP/IP Adaptation to Heterogeneous Network
Environment
APOHN Architecture adds Subnetwork Layer to the protocol stack
Optimized Subnetwork Protocols, Flow Multiplexing, and Protocol Speedup are keys for Performance enahncement
IPSec is Supported
Dzmitry Kliazovich (klezovic@dit.unitn.it)April 4, 2006
Thank you!
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