APOHN: Subnetwork Layering to Improve TCP Performance over Heterogeneous Paths April 4, 2006 Dzmitry Kliazovich, Fabrizio Granelli, University of Trento,

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


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)


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


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


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


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


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


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.


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


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


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


Related Works Performance Enhancement Proxy (PEP)


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


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)


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


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


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


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


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


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


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


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


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


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


Thank you!

Documents

APOHN: Subnetwork Layering to Improve TCP Performance over Heterogeneous Paths April 4, 2006 Dzmitry Kliazovich, Fabrizio Granelli, University of Trento,