Bidirectional Light-Trails Dzmitry Kliazovich, Fabrizio Granelli, University of Trento, Italy GLOBECOM’05 November 29, 2005 Hagen Woesner, Imrich Chlamtac

BidirectionalLight-Trails

Dzmitry Kliazovich,Fabrizio Granelli,

University of Trento, Italy

GLOBECOM’05November 29, 2005

Hagen Woesner, Imrich Chlamtac

CREATE-NET

Dzmitry Kliazovich ([email protected])November 29, 2005

Outline

Light-Trails and Internet Traffic

Bidirectional Light-Trails Bidirectional Synchronious Protocol (BLSP)

Conclusions


Light-Trails

Light-Trail – an opened optical bus for unidirectional multi-point communications

Established out-of-band in separate control channel

Ref.: A. Gumaste and I. Chlamtac, "Light-trails: a novel solution for IP-centric communication," in Workshop on High Performance Switching and Routing (IEEE, New York, 2003).


Light-Trails

Advantages Wavelength reuse based on spatial separation On-demand channel access

Drawbacks Unfairness – nodes located upstream always get

priority in channel access No upstream signaling


Internet Traffic

Internet Traffic Behavior Client-server applications Request-response protocols (HTTP, FTP, POP) Dominant TCP protocol (>85%) acknowledges data in backward

direction Multimedia applications (Videoconferencing, VoIP)

More than 90% of Internet traffic is bidirectional!

Requires two light-trails in opposite directions between sender and receiver


Bidirectional Light-trails (BDLT)

BDLT – an organization of two separate light-trails connecting a set of nodes in two directions (uplink and downlink) allowing bidirectional communication

R x T x

R xT x

N 1

R x T x

R xT x

N 2

R x T x

R xT x

N 3

R x T x

R xT x

N 4

D o w nlink

U p link

D W -c o nvener

U P -end

D W -end

U P -c o nvener



Bidirectional Light-Trail Set Up Select two available wavelength: one

in forward, another one in backward direction

Start switch configuration upon control packet reception

Last node generates the acknowledgement

Set Up time:

N 1 N 2 N 3 N 4

t1

t2

t3

t4

t5

C o n tr o l P ac k e tP r o c es s in g T im e

AC K P ac k e tP r o c es s in g T im e

O p tic a l S w itc hC o n f ig u r a t io n T im e

t6

t7t8

t9t1 0

t1 1t1 2

t1 3Tset-up = 2h(tp + tpr)

h – number of hops;tp – propagation delay between nodestpr – packet processing delay



Light-Trail Dimensioning Similar to Light-trail set up using control packets

Dimensioning Metrics Traffic Monitoring Bandwidth Utilization

Unidirectional Light-Trail Only downstream nodes observe traffic at the upstream part Light-trail end can be extended

Bidirectional Light-Trail Bidirectional In-band Signaling Full control on light-trail size / bandwidth utilization


Bidirectional Light-trail Synchronous Protocol

Supports data communications at the link layer as well as signaling

Superframe is divided into: Reserved Bandwidth Period – scheduled channel access Unreserved Bandwidth Period – on-demand channel access

Reserved Bandwidth Period Bandwidth Reservation Requests Schedule Announcement Data Delivery



The size of Reserved BW period is variable Based on reservation request received in prev. superframe

Data delivery slots are flexible (not as in fixed TDM)

S YNR S V

R S V1

. . . R S V( N - 1 )

D AT A1

. . .D AT A

N

R es ervatio n D ata D elivery

S up erfram e

S c hed uleA nno unc em ent

S C H1

. . .S C H

K

R es erved B W

S YNUN R S V

UN R S V D AT A

U nres erved B W



Communication Overhead

Link Speed (Gbps)

Number of nodes

Overhead (bytes)

Overhead (%)

Utilization (%)

1

10 245 1.57 98.43

50 1205 7.7 92.3

100 2405 15.39 84.61

10

10 245 0.15 99.85

50 1205 0.77 99.23

100 2405 1.54 98.46


Evaluation Results

OPNET simuations Light-Trail: 5 nodes, 80 km length Superfame size: 125 us

Simulation focus Fairness Channel Access Delay Bandwidth Utilization


Evaluation Results

Bandwidth Sharing (Per-node Fairness)

0

200

400

600

800

1000

0 1 2 3 4Simulation time (sec)

Thr

ough

put (

Mbp

s)

Node N1

Node N2

Node N3Node N4


Evaluation Results

Channel Access Delay Mostly determined by the node’s position from the light-trail

head Less dependant on the superframe size

0

0.2

0.4

0.6

0.8

0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1Simulation time (sec)

Del

ay (

mse

c)

Node N1

Node N2

Node N3

Node N4


Evaluation Results

Goodput and Bandwidth Utilization


Conclusions

Bidirectional Light-Trails (BDLT) are proposed as an extension of the Light-Trail concept in order to take advantages from in-band signaling motivated by bidirectional nature of the Internet traffic

Ongoing research deals with bidirectional architectures as well as with other types of access protocols which can minimize channel access delays


Thank you!

Documents

Bidirectional Light-Trails Dzmitry Kliazovich, Fabrizio Granelli, University of Trento, Italy GLOBECOM’05 November 29, 2005 Hagen Woesner, Imrich Chlamtac