1. A Bandwidth-Efficient and Low-Latency Packet Assembly Strategy for Optical Burst Switching in Metro Ring
Prasanna Krishnamoorthy, Andrea Fumagalli
Optical Networks Advanced Research (OpNeAR) Lab.,
Erik Jonsson School of EECS, University of Texas at Dallas
Burst Switching
LightRing Architecture
LightRing Advantages
Packets from a flow – same source, destination and class – are aggregated to make bursts
These bursts, are transmitted all-optically through the core of the network
Benefit
Lower overhead
Allows slower optical switching speeds 4
No loss
In lossy Burst switching networks, larger bursts cause higher packet loss probability
LightRing is lossless, hence we can build bigger bursts
Ring topology
Since path and intermediate nodes are known, aggregation can be done across multiple destinations
Ring topology
Multi-wavelength
All-optical
Token-based access protocol
Loss-free, bandwidth on-demand
Spatial Reuse 3 5 2 6 l1 l2 l3 1 7 8
Node Architecture
Optical Burst Add Drop Multiplexer (OB-ADM)
Aggregation Protocol
QoS Protocol
Different aggregation possibilities
Same source, destination and class (S/D/C)
Same source, destination, different classes (S/D)
Same source, different destinations and classes (S)
Aggregating different packet flows provides even better bandwidth efficiency
more packets travel on the same burst
number of burst requests go down
latency goes down due to many flows being multiplexed
Larger bursts can be created quicker due to lossless nature of LightRing !
Source OB-ADM node
receives packets from external connection.
aggregates packets into a burst
transmits bursts all-optically to destination
Destination OB-ADM
de-multiplexes the packets from the burst
transmits out of the network
Token has a counter
Counter keeps track of outstanding real-time traffic at all the nodes
If counter increases, then best-effort traffic is not allowed onto the ring
Only if counter decreases, best-effort traffic is allowed onto the ring
Response Time Vs Throughput
Variation with Ring Size
a/D with Varying Load
Summary
Lossless transmission allows greater efficiency – since each burst can be larger
Ring topology – intermediate nodes are known – allows same burst to have packets for different destinations
Larger bursts more efficient (less overhead)
Since more flows are used, bursts can be built quicker – lower latency
16 Nodes, 4 x OC-192, 80km
16 Nodes, 4 x OC-192
16 Nodes, 4 x OC-192, 80km