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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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])April 4, 2006
Related Works Performance Enhancement Proxy (PEP)
Dzmitry Kliazovich ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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 ([email protected])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