New Networking Architectures and Technologies

1
New Networking Architectures and Technologies

• Martin Zirngibl
• Director, Bell Labs Research
• mz_at_lucent.com
• Dimitri Stiliadis, Peter Winzer, Harsha Nagesh,
  Vishy Poosala

2
Background

• Fiber amplifier and WDM have allowed orders of
  magnitude increase in point-to-point bandwidth
• Data traffic dominates, but voice traffic still
  creates most revenues
• Problems
• Switching has become bottleneck
• Legacy networks not optimized for data traffic
• Outline of Talk
• Are there network architectures that can be
  efficient for both, voice traffic and data
  traffic?
• How can we scale SONET/SDH networks?
• How can we scale packet switches?

3
Network Architectures for Bursty Traffic

• Point-to-Point
• Logical point-to-point
• Use SONET/SDH layer for muxing
• Packet Switched
• Muxing is done in IP
• Burst Switched
• Dynamic provisioning of the network resources
• Load-Balanced
• New proposal to combine advantages of
  point-to-point and packet switched.

4
Statistical Multiplexing
Bandwidth demand

• Statistical Muxing aggregates Bandwidth gt Better
  Efficiency
• Will be used when traffic is bursty and bandwidth
  expensive

C
C
C
Packet Buffer And mux
C
C
Total demand

• Where will statistical muxing be used, core or
  edge?
• Not Clear Because
• Edge bandwidth Bursty but Transport Cheap
• Core Traffic Smooth but Bandwidth Expensive

5
Todays Network Architecture
Logical mesh Between edge and access routers
High Order Circuit Switching (STS-1)
High Order Circuit Switching (STS-1)
Data over SONET
Enterprise Data Access DSO/DS1/DS3
HUB
POP Ethernet Network
SONET/WDM Optical Core
Low Order Circuit Switching (VT1.5)
Enterprise Voice DSO/DS1
TDM
Core Routers
Edge Routers ATM/Frame Relay
Circuit switched core SONET/SDH optical
Circuit-switched access network
Packet aggregation on customer premise
Packet aggregation At edge of core network
6
Statement of the Problem

• N nodes want to exchange packet traffic
• Each node wants to deliver and receive packets
  at an average rate C
• Packets from any node may go to any other
  node(s) at a rate(s) between 0 and C

C
C
C
C
1
2
C
Demand X to Y
3
4
C
C
C
C
time
7
Solution 1 Point-to-Point Bandwidth of Cbetween
all Nodes

• Requires Transport Network with N(N-1)C
  Bandwidth
• Logical Point-to-Point can be provided through
  SONET network
• - Very inefficient for bursty traffic
• Transport Network Static
• No Packet Switching Necessary in Intermediate
  Nodes (Single Hop Routing)

C
C
C
1
2
C
3
4
C
C
C
C
gt Preferred Solution When Bandwidth is Cheap or
Traffic is Static
8
Solution 2 Multi-Hop Packet Switching

• Nodes Are Packet Routers
• Each Node is Only Connected to Nearest Neighbors
• Requires Transport Network with NC Bandwidth
• Very efficient for bursty traffic
• Transport Network Static
• - Intermediate Nodes Complex and Costly

C
C
C
1
2
C
3
4
C
C
C
C
gt Preferred Solution When Bandwidth is Expensive
and Traffic is Bursty
9
Solution 3 Burst Switching
Switch Transport bandwidth the Follow Traffic
Pattern gt Transport network Dynamic Needs NC
Transport Bandwidth Needs Global Control Plane
(MPLS, ATM, .)
C
C

• Complex Network control
• Cannot follow traffic faster than time
• of-flight changes (ms)
• Needs large buffers
• Latency and probability of loss issues

C
C
1
2
3
4
C
C
C
C

• Complexity of control plane and intrinsic slow
  response
• is a problem for this technique

10
Solution 4 Load-Balancing

• Send C/N traffic to every node
• Needs 2NC bandwidth
• Packet routing Less Complex than in IP-router
  Network
• Transport network static
• will work for any traffic pattern

C
C
C
1
2
C
3
4
C
C
C
C

• New Solution that eliminates packet switching,
• no new control planes needed.

11
Load-Balancing Capacity Comparison
Uni-Directional Ring
Mesh Network
C
C
1
2
C
C/N
C
C/N
3
4
C
C/N
C
C
C
12
Conclusions Network Architectures

• Load balancing
• scales more favorably in transmission capacity
  than point-to-point (by factor 2/N)
• scales more favorably in packet switching
  requirements than IP (by factor N)
• scales more favorably in circuit switching
  capacity than point-to-point (by factor 2/N)
• TDM network sufficient

• Some other benefits
• No global control plane, topologic maps, etc.
• No node ever sees full information (high degree
  of data security)
• Easy restoration possible (overhead packets,
  similar to FEC)

• Some open questions
• Latency (more time of flight propagation delay,
  but single-hop routing)
• Required resequencing buffer sizes

13
The Next Step

• Load-balancing takes THRU traffic from layer 2/3
  into layer 1 (SONET/SDH/MPLS) gt simplified
  switches, but still needs O-E-O for all THRU
  traffic
• Can we take the THRU traffic from layer 1 into
  physical layer gt no O-E-O on THRU traffic?

14
The SONET/SDH Ring Scalability Problem

• SONET ring
• Good granularity (STS-1) but
• O-E-O, data processing at each node
• Amount of thru-traffic increases withnumber of
  nodes
• ? limited scalability
• WDM ring
• Connect nodes with static wavelengths
• Good scalability, but
• Granularity too coarse
• N-1 transponders at each node
• ? Expensive solution

15
Time Multiplexed WDM (T-WDM) TDM Aggregation
Traffic De- aggregator
Traffic Aggregator
10 Gb/s
16
Time Multiplexed WDM (T-WDM) Coloring the Packets
Traffic Aggregator
Filter
10 Gb/s

• T-WDM
• Allows to connect in all-optical domain
  sub-wavelength granularity channels
• Routes channels with simple, passive optical
  filters
• Scalability of WDM
• Granularity of SONET

17
Solution Time-Multiplexed WDM

• T-WDM SONET ring
• Drop single wavelengthat each node
• Tunable transmitters provide WDM connections
  without intermediate O-E-Os
• Time-multiplexed packet transmission (TDM)
  provides fine bandwidth granularity
• Periodic global schedule provisions capacity
  between nodes and ensures 100 throughput and
  fixed low latencies

18
T- WDM Ring
19
Performance Comparison for N-Node Ring

• T-WDM has Bandwidth Granularity of SONET
• T-WDM has Scalability and Efficiency of WDM

20
Experimental Setup

• OC-12 generator produces scrambled SONET frames
  with PRBS 231-1 payload
• Unused 10 Gb/s time slots are filled with dummy
  packets
• All Txs switch packets based on a global,
  periodic schedule
• De-aggreators reassemble packets with SONET data
  back into OC-12 stream
• BER measurements on OC-12 outputs
• Span 1 21 dB, 400 ps/nm. Span 2 22 dB,
  -100 ps/nm

21
Fast Tunable Laser Module
3
2
SG -DBR Laser
Gain Source
Wavelocker
TEC Control

• Tunes between 64 ITU channels in less than 45 ns
• Wavelocker feedback improves frequency accuracy
  and prevents long-term drift

Without Locker
With Locker
22
Aggregator / De-Aggregator Hardware
10 Gb/sPackets out
10 Gb/sPackets in
10 Gb/s Mux(161) board
10 Gb/s Demux(116) board
AggregatorFPGA
DeaggregatorFPGA
15 x OC-12(622 Mb/s)Data out
15 x OC-12(622 Mb/s)Data in
23
Aggregator creates Optical Data Packets

• Aggregator FPGA compresses622 Mb/s chunks by
  factor 16 in time and adds dead time and training
  pattern
• 15 packets in 16 time slots? overhead 1/16 (lt
  7)? dead time training pattern equals
  1/16 of payload
• Currently, the aggregator receives one OC-12
  stream and creates 14 dummy packets for every
  real data packet
• Extension to multiple OC-12 channels to be
  programmedin the near future

1.4 ms
64 ns
25 ns
24
BER measurements

• BER of OC-12 data versus optical power of 10 Gb/s
  packets
• small penalty (lt 0.5 dB) between back-to-back and
  node-to-node transmission
• T-WDM can tolerate 24 dB span loss and 400
  ps/nm and -100 ps/nm dispersion

25
Scheduling Similarity of T-WDM and PON
Time-multiplexed WDM
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Tx
Rx
Upstream Passive Optical network
Tx
Tx
Tx
Nx1 Passive Combiner
Tx
Tx
Rx
Tx
Tx
26
Summary T-WDM

• T-WDM has bandwidth granularity of SONET
• Grooming in optical domain
• Aggregation/deaggregation similar to ATM
• Single 10Gtransmitter shared over multiple
  end-nodes
• T-WDM has scalability and cost-efficiency of WDM
• Multiple wavelengths simultaneously in fiber
• Optical Add/drop
• Periodic scheduling assures 100 efficiency and
  SONET like QoS
• Key technologies
• Fast tunable transmitters
• Burst-mode receivers
• Aggregator/Deaggregator
• Global scheduler

27
Benefits of Load-Balancing in Packet Routers

• Removes Central Scheduler
• Only local decisions per port-card
• Much better scalability for scheduling
• Guarantees close to 100 throughput
• Replaces Switch Fabric by Hard-Wired Bandwidth
• Allows to reuse STS1 fabric of a SONET xconnect
• Fabric does not need to be strictly non-blocking
• Fabric complexity of O(N) instead of O(N2)
• 1N protection scheme
• Graceful upgrade

28
Request by US Defense Agency A Scalable Optical
Router

• Optical Router Architecture Scalable to gt100Tb/s
• Believe is that current router architecture will
  not scale to more than a few Tb/s throughput
• Main Bottleneck is electronics
• No Electronics in Data-Path
• Complicated functions like regeneration,
  buffering, header recognition must be implemented
  in optics
• Innovative All-optical Signal Processing and
  Buffering Techniques
• Currently known techniques do not allow for above
  processing functions
• Push Density of Monolithic Integration
• DARPA believes that optical technologies must
  follow path of electronics to achieve high levels
  of functionality

29
Bell Labs won 12.5M Research Contract with IRIS
Proposal

• Optical Three Stage Load-Balanced Architecture
• Solves Scheduling problem
• Optimally Designed to Take Advantage of Simple
  Buffers
• High Scalability Because Does Not Require
  Strictly Non-Blocking Stages
• Photonic Integrated Circuit (PIC) with more than
  100 Semiconductor Optical Amplifier
• Regenerative Multi-Wavelength Switch
• Optical Time Buffer
• Multi-Wavelength Optical Header Look-Up
• Total Throughput Scales To 256 Tb/s, 6400 Ports
  at 40Gb/s
• Exploit Space and Wavelength Dimension
• Wavelength Routing in a 80x80 AWG on 80
  Wavelength Channels
• Wavelength Switching Below 1 ns

30
Wavelength Switching
Buffer
From Input Port
Output
T-Tx
40G Rx
retiming
T-Tx
40G Rx
Sche- duler
T-Tx
40G Rx
T-Tx
40G Rx
Clock
31
N2 Scalability of the AWG
wavelength
insensitive
Combiners
10
Arrayed
Waveguide
Output Ports
Input Ports
Grating
32
Conclusions

• Scalability of current networks architecture for
  data traffic is an issue
• SONET/SDH inefficient because not statistical
  muxing
• Packet switched networks very complex
• WDM networks have too coarse bandwidth
  granularity
• Load-balancing allows for more scalability
• Static SONET/SDH network can now be used for
  statistical muxing across network.
• Removes scheduling bottleneck from packet
  switching
• Allows for optical switching technology
• T-WDM for scaling SONET/SDH
• Maintains bandwidth granularity of SONET/SDH
• Scalability of WDM