The document discusses optical interconnect technology for routers. It describes how conventional copper interconnects have limitations like power consumption and distance, while optical interconnects using fibers can transfer data over longer distances with lower power. The D-chip is presented as the first commercial router product using optical interconnect between silicon chips. It provides over 1 terabit per second bandwidth density and can scale to support future networking needs. The document also outlines how an output queued router architecture using optical interconnects between line cards improves performance for multicast traffic compared to a conventional router design.

1. Compass-EOS for Linkmeup
Alex Clipper 17/1/15

2. Agenda
Conventional chip review
D-Chip review
Standard carrier-grade router architecture
Compass-EOS router architecture
Dev-test methodologies
Questions

3. D chip on the map
3600
412 mm2

4. 4
Zooming in on the challenge

5. Data Transfer Between CMOS Processors
The Conventional Way
 Electrical transmission via Copper
 Loss is frequency dependent
 High Power consumption as
additional electronics are needed to
compensate for the signal loss
 Limited Interconnect length
The Compass Way
 Using photons in fibers to transfer the data
 Parallel optics are used to achieve high BW
 Small interconnect footprint (10% of the total chip
area)
 Low Power consumption
 Negligible Loss, supports long distances (>200m)
CMOS
Serial Links
Traffic-in Package
Tx Matrix Rx Matrix
FibersTraffic-out
CMOS
CMOS
Fibers

6. Compass Multi Terabit interconnect
First Commercial Implementation – The D-chip
Tx
Rx

7. icPhotonics™ - Fastest Optical Interconnect
1.34Tb/s Full Duplex Bandwidth
Order of magnitude higher Chip
I/O Density. 64Gb/s per mm2
Passive optical links that stretch to
Hundreds of Meters vs.
Centimeters with Electronics
• Direct Coupling to CMOS Chip
• Low energy consumption: 10pJ/bit
• Dozens of Patents Covering
Technology & Processes
• Flexible form factor
• Ready for Mass Production
Laser
Matrix
Photo
Detector
s
Standard
I/O
Digital
CMOS chip
Direct
optical
interface

8. 1.34 Tb/s In
Fiber Optic Bundle
Compass Optical Interconnect
Half bundle illuminated
1.34 Tb/s In

9. The enabling Technology
2 x 350G
2 x 1344G
 Low Power – 2.7T at < 15 W
 High Density – 2.7T in 40 mmSQ
 Future Proof – Protocol Agnostic Technology
 Very Scalable – 20T+ per Slot
BW density 30X

10. ASR9k LC Architecture

11. A simple Multicast scenario, fabric links normalized at 100G
Multicast in conventional architectures
Ingress
buffer
Switch
Fabric
Forward
From
Fab
Forward
Egress
buffer
ToFab
Buffer
Ingress
bufferForward
From
Fab Forward
Egress
buffer
ToFab
Buffer
Ingress
bufferForward
From
Fab Forward
Egress
buffer
ToFab
Buffer
Ingress
bufferForward
From
Fab Forward
Egress
buffer
ToFab
Buffer
30G Multicast stream
100Gbps
100Gbps
100Gbps
100Gbps
30G Unicast stream
30G Unicast stream
30G Unicast stream
Congestion
• From fab resource on egress card congested
Back pressure
• Back pressure (BP) is signaled to all ingress
cards
X
X
X
• In response to BP, all ingress cards reduces
transmit rate towards the congested card
30G Multicast stream
X
• Multicast traffic to non-congested egress
cards can in worst case also be impacted !
X
?!?
?!?
Affected stream direction (streams with packet loss)

12. Operation of a distributed router system
 Line cards comprises several
Silicon processors performing
different functions (Queuing,
Forwarding etc.)
 Data needs to be exchanged
between these Silicon chips.
 The interconnect can be chip
to chip, board to board or
chassis to chassis.
 Data transfer rate between
processors is a significant
factor when it comes to router
performance

13. MAC
NPU
Egress
Buffers
D-chip
100Gbps
100Gbps
100Gbps
30G Multicast stream
30G Unicast stream
30G Unicast stream
30G Unicast stream
30G Multicast stream
MAC
NPU
Egress
Buffers
D-chip
MAC
NPU
Egress
Buffers
D-chip
MAC
NPU
Egress
Buffers
D-chip
• Egress interface is congested
Congestion
• Egress interface queuing have full visibility of all
traffic to this egress destination and handle
packets according to operator SLA priorities.
• No impact on Traffic destined for ports on
same or other cards
A simple Multicast scenario, Backplane links normalized at 100G
r10004 architecture

14. Compass EOS - Evolving Router Architectures
Ingress
buffer
Forward
ToFab
Buffer
From
FabForward
Egress
buffer
Ingress
buffer
Forward
ToFab
Buffer
From
FabForward
Egress
buffer
Egress
buffer
Ingress
buffer
Egress
Buffer
Ingress
buffer
Forward
Forward
ToFab
Buffer
From
Fab
ToFab
Buffer
From
Fab
ToFab
Buffer
From
Fab
ToFab
Buffer
From
Fab

15. Compass EOS – Router Architecture
Ingress
Forward
engine
Egress
Forward
engine
Ingress
Buffer
Queing &
Egress
Buffer
Ingress
Forward
engine
Egress
Forward
engine
Ingress
Buffer
Queing &
Egress
Buffer
To
switch
Buffer
From
switch
Buffer
To
switch
Buffer
From
switch
Buffer
Input ports
Input ports
Output ports
Output ports
D
D
•Queing
•Egress Processing
•Egress Buffer
•Queing
•Egress Processing
•Egress Buffer
•“Switch fabric” Router The Compass way
• Chip to Chip Optical inter-connect
• True Output Switched Router
• Switch Fabric eliminated
• No ingress side queuing
• Maintaining all of the functionality

16. DP components – the LC
iNP
Interlaken 150G
Interlaken 100G
Interlaken 150G
Interlaken 100G
eNP
D
eBufferiBuffer
iBuffer
Interlaken 60G
Interlaken 60G
Interlaken 60G
Interlaken 60G
D
eBuffer
Interlaken 100G
Interlaken 150G eNP
Interlaken 100G
Interlaken 150G
iBuffer
iBuffer
Interlaken 60G
Interlaken 60G
Interlaken 60G
Interlaken 60G
IL 30G
L2 FPGA
PMC
SFP+
SFP+
L2 FPGA
L2 FPGA
L2 FPGA
PMC
SFP+
SFP+
PMC
SFP+
SFP+
PMC
SFP+
SFP+
PMC
SFP+
SFP+
PMC
SFP+
SFP+
PMC
SFP+
SFP+
PMC
SFP+
SFP+
PMC
SFP+
SFP+
PMC
SFP+
SFP+
IL 30G
IL 30G
IL 30G
IL 30G
IL 30G
IL 30G
IL 30G
IL 30G
IL 30G
IL 30G
IL 30G
CPU Module
10GE
TCAM
TCAM
iNP
TCAM
TCAM

17. Compass-1: Overview
800Gbps system
6 RU , 19” shelf
4 x Line Cards
Optical BP
Front to Back air flow
Distributed DC Power Supply
80x10GE, 8x100GE

18. Summary Full Mesh advantages (Real Output Queue)
Ease of QoS configuration
What you configure is what you get
Packet drop takes place where you have full visibility
Better Multicast scale
Better system security
More accurate SLA
Predicted and deterministic behavior
D iNP eNP
D iNP eNP
CPU
mac
mac
mac
mac
mac
D iNP eNP
D iNP eNP
CPU
mac
mac
mac
mac
mac
D iNP eNP
D iNP eNP
CPU
mac
mac
mac
mac
mac
eNP iNP D
eNP iNP D
CPU
mac
mac
mac
mac
mac
CPU MEM MEM
CPU MEM MEM
CPU MEM MEM
CPU MEM MEM