CSE 291A Interconnection Networks

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CSE 291-aInterconnection Networks
Lecture 12 Deadlock Avoidance
(Contd)Router February 28, 2007 Prof.
Chung-Kuan Cheng CSE Dept, UC San Diego Winter
2007 Transcribed by Yi Zhu
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Topics

• Deadlock avoidance
• Restricted physical route (lecture 10)
• Resource classes
• Distance classes
• Dateline (ring)
• Duatos protocol
• Router Architecture

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Distance Classes

• classes gt diameter of network
• At source, we inject packets into resource of
  class 0
• At each hop, the packet of class i acquires a
  resource of class i1
• Use min routing

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Dateline (Ring)

• There are two classes
• A dateline cuts the ring into a string
• At source, we inject packets into resources of
  class 0
• Packets remain in the same class, but jump to
  class 1 when crossing the dateline

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Dateline (Ring)
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Duatos Protocol for Deadlock-Free Adaptive
Algorithm

• The underlying network is deadlock-free. The
  routing relation is R1 escape routing
• Create new virtual resources and routing relation
  Rc
• Rc -gt R1 works as injection at the node.
• R1 -gt Rc not allowed

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Router Architecture
state
Physical channel
Physical channel
buffer
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Virtual Channel State

• Virtual channel state fields 5-vector GROPC
• G Global state
• I (idle),
• R (routing)
• V (waiting for VC)
• A (active)
• C (waiting for credits)
• R Route, output port R for the packet
• O Output VC, output VC O of port R

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Virtual Channel State (Contd)

• P Pointers, flit head and flit tail pointers
  into the input buffer
• C Credit count, credits C for VC O of port R