Optics and Routing Seminar

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Optics and Routing Seminar Whats next?
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Goal of this talk

• To propose a strawman system that has
  interesting research problems in the areas of
• Optics and optical switching,
• Networking and networking system design, and
• Circuit and interconnect design.

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Overall SystemThe Stanford Phicticous Optical
Router?

• 100 Tb/s Internet Protocol Router, arranged as
  625 linecards, each operating at 160Gb/s.
• Rationale
• Hard but not impossible.
• An Internet Router is well-defined, well-known
  and relevant.

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Generic 100Tb/s IP Router
Switch
Linecard 625
Linecard 1
160- 320Gb/s
160- 320Gb/s
40Gb/s

• Line termination
• IP packet processing
• Packet buffering

• Line termination
• IP packet processing
• Packet buffering

40Gb/s
160Gb/s
40Gb/s
Arbitration
Request
40Gb/s
Grant
5
IP Header
0
16
31
Total Length
Version
Service
HLEN
Datagram ID
Flags
Fragment Offset
TTL
Hdr checksum
Protocol
20B-64kB
Source address
Destination address
Data
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IP Router Requirements

• Lookup packet IP destination address in
  forwarding table.
• If known, forward to correct port.
• If unknown, drop packet.
• Decrement TTL field, update header checksum.
• Buffer packet until switch is available for
  transfer.
• Forward packet to outgoing interface.
• Wait turn to be transmitted.
• Transmit packet onto outgoing link.

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Basic Flow
Egress Linecard
Ingress Linecard
Buffer
Buffer
Forwarding Table
625x625 Switch
160- 320Gb/s
160- 320Gb/s
160Gb/s
160Gb/s
IP Lookup
Packet parse
Buffer Mgmt
Buffer Mgmt
Request
Arbitration
Grant
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Basic Flow
Egress Linecard
Ingress Linecard
Buffer
40Gb/s
Forwarding Table
40Gb/s
Packet parse
625x625 Switch
IP Lookup
Buffer Mgmt
160- 320Gb/s
160- 320Gb/s
Buffer
Forwarding Table
40Gb/s
40Gb/s
Packet parse
IP Lookup
Buffer Mgmt
Buffer
Forwarding Table
40Gb/s
40Gb/s
Request
Packet parse
Arbitration
IP Lookup
Buffer Mgmt
Grant
Buffer
Forwarding Table
40Gb/s
Packet parse
40Gb/s
IP Lookup
Buffer Mgmt
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Linecard Questions

• Packet buffering at 40Gb/s and 160Gb/s With 64B
  units at 40Gb/s, one read/write every 6.4ns.
• IP Lookup at 40Gb/s and 160Gb/s At 160Gb/s, at
  least one data-structure access every 2ns.
• Power efficient packet processing.

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Various Approaches Switching and Arbitration

• Approach 1
• Switch datapath electronic direct-attached
  VCSELreceiver
• Arbitration electronic
• Approach 2
• Switch datapath MEMs switch(es)
• Approach 3
• Switch datapath Tunable lasers and passive
  coupler.
• Approach 4
• Switch datapath Multistage switch.

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Approach 1
1
625x625 Crossbar 2.5Gb/s per I/O
2
Egress Linecard
Ingress Linecard
160Gb/s
64-128
160Gb/s
Grant
Arbitration
Request
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Approach 1Switch datapath
625x625 Crossbar 2.5Gb/s per I/O

• 625 VCSEL and detectors at 2.5Gb/s
• 625x625 digital, synchronous crossbar
• For power to be lt 20W per chip, requires TxRx
  lt 35mW

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Approach 1Arbitration
Ingress Linecard
At 320Gb/s, 64B every 1.6ns 1600B every
40ns 40kB every 1us 40MB every 1ms
160- 320Gb/s
160Gb/s
Grant
Arbitration
Request
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Approach 1Arbitration Load-balancing
1
625x625 Crossbar 2.5Gb/s per I/O
2
Arbitration
Egress Linecard
Ingress Linecard
Arbitration
160Gb/s
160Gb/s
Request
64-128
Arbitration
Grant
At 2.5Gb/s, 64B every 200ns
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Approach 2MEMs switching
Pairs of MEMs crossbar elements. One passes data
while the other is configured.
A
Egress Linecard
Ingress Linecard
B
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Approach 2MEMs switching
A
B
Egress Linecard
Ingress Linecard
Arbitration
A
B
Arbitration
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Approach 3
Egress Linecard i
Ingress Linecard
li
li l1 l2
Passive Optical Coupler
Arbitration
Fixed or pseudo-fixed wavelength detector
Fast tunable Laser or array of VCSELs
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Action Plan

• Lets split the architecture into three parts
  Linecard, Switch Datapath, Arbitration.
• Lets form at least three groups each group
  works on one part.
• Each group report back with a proposal in ???
  weeks.