Hybrid Switching

1. Down to the Bottom:
Innovation from Below
Dae Young KIM
Chungnam Nat’l Univ.
cnu.ac.kr/~dykim
20-May-06/KCIST dykim@cnu.ac.kr 1

2. Internet Hurdles
 Quality of Service
 Multicast
 Mobility
 Security
 …
20-May-06/KCIST dykim@cnu.ac.kr 2

3. Why Internet fails
 Internet tries to implement the
advanced features in the IP layer.
 Yet, essential networking features
should be implemented within the
(sub-)Network Layer and below, not in
the Internetworking (IP) Layer.
 IP just for global addressing & reach
 “Connectivity is its own reward.”
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4. Network Design Goals
 Provide essential features intrinsic
 QoS
 Multicast
 Fast mobility
 Availability of L1 and L2 information
 Security
 …
 Instantaneous seamless (w/o
signaling) transport of BE IP packets
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5. Back to the Basics
 Circuit Switching:  Packet Switching
 Guaranteed QoS  Best-effort
 Expensive  Cheap
 Wasteful of  Exploiting the
bandwidth bandwidth
 CO operation  CL operation
 Telco-centric  Computer-centric
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6. Circuit Switching is Expensive?
 Due to:
 Over-specification; five-9 in OAM&P, MTBF, ...
 Network is too smart
 Telco Monopoly
 Can be made drastically cheaper:
 Loosened specs
 Data is over 90% of all
 Packet back-up is available
 TDM chips are cheap
 Open-ended competition among network/service
providers
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7. Circuit over Packet
 Circuit emulation not e2e scalable
 Too many states to manage
 Excessive consumption of resources
 Circuit-like, but never really is one.
 Hop-by-Hop emulation an alternative
 Challenge: Uncompressed HDTV for
military/medical/physics applications
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8. Packet over Circuit
 QoS comes as default.
 Less states management
 States (quasi-)static, not dynamic
 Can be made to load BE packets
signaling-free onto circuits
 Multicast may come intrinsic
 Ckt better for security enforcement
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9. Now What?
 Ultimately, people will expect you to deliver
uncompromised HDTV in the same pipe as you do
IP packets.
 Until then, they'll never be happy, you'll never be
dismissed.
 Sorry, the world is divided into two, and you have
to take a side:
 either Packet or Circuit
 Or you're just a believer in the theory:
 They'll eternally go in parallel, like railways;
 Always two pipes to your home and office.
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10. Two Schools
 Circuit over Packet
 IEEE 802.1as: A/V Bridging
 QoS WiFi?
 Packet over Circuit
 Hybrid Switching
 FireWire (IEEE 1394)
 Bluetooth
 WiMAX / WiBro
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11. Hybrid Switched Network
 Based on synchronous slots
 Hybrid Transfer Mode (HTM)
 QoS data taking on slots periodically
 BE packets flows thru the rest of slots
 Hybrid Switch
 TDM switch + Packet switch
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12. HTM: Hybrid Transfer Mode
User
Header
t0 t1 t2 t3
CO slot
A Buffer CL slot
Idle slot
B To Remote
C
D
A B B D B B C B A B B B B B C B
Cycle1 Cycle2 Cycle3 Cycle4
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13. Slot format
10 9 8 7 6 5 4 3 2 1
H eader P a y lo a d
S lo t f o r m a t
01 P a y lo a d 1 10 P a y lo a d 2 11 P a y lo a d 3 01 P a y lo a d 1 00 P a y lo a d 2
C L t r a f f ic C O t r a f f ic C L t r a f f ic I d le t r a f f ic
0 0 ; I d le s lo t , 0 1 ; S t a r t o f C L t y p e , 1 0 ; C o n t in u a n c e M e a s a g e o f C L T y p e 1 1 ; C O t y p e
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14. HTM Switch Structure
R o u t in g M o d u le
C o o r d in a t o r
A d m is s io n C o n t r o l/ C o n t r o l
S ig n a lin g P r o c e s s in g
C o n tro l T D M S w itc h
D a ta
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15. Hybrid Switch
Buffer
R outer H eader H ig h P r io r it y L o w P r io r it y
M o d u le I n s e r t io n
Packet table lookup
r e a s s e m b le r
O utput
H eader
S lo t
E x tracter C ut-through
Interface
Inserter
CL
S e r ia l
CO /CL
C la s s if ie r
S w it c h M o d u le
CO
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16. IEEE 802.1as: A/V Bridging
- synchronized switches -
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17. IEEE 802.1AS: A/V Bridging
- topology & connectivity -
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18. Conclusion
 Implementing advanced features in
the IP layer is a false dream.
 IP simply for connectivity
 Hour- or wine- glass model
 Seek innovation with smart design in
the lower layers.
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19. References
 D. Y. Kim, “Hybrid Switching”, internal
notes and papers, 1996~
 http://www.ieee802.org/1/pages/avb
ridges.html
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