Lecture 9 - Åbo Akademi
Lecture 9 - Åbo Akademi Lecture 9 - Åbo Akademi
Routing algorithms • Routing algorithm must ensure freedom from livelocks • livelocks are similar to deadlocks, except that states of the resources involved constantly change with regard to one another, without making any progress • occurs especially when dynamic (adaptive) routing is used • e.g. can occur in a deflective “hot potato” routing if a packet is bounced around over and over again between routers and never reaches its destination • livelocks can be avoided with simple priority rules • Routing algorithm must ensure freedom from starvation • under scenarios where certain packets are prioritized during routing, some of the low priority packets never reach their intended destination • can be avoided by using a fair routing algorithm, or reserving some bandwidth for low priority data packets
Flow control schemes • Goal of flow control is to allocate network resources for packets traversing a NoC • can also be viewed as a problem of resolving contention during packet traversal • At the data link-layer level, when transmission errors occur, recovery from the error depends on the support provided by the flow control mechanism • e.g. if a corrupted packet needs to be retransmitted, flow of packets from the sender must be stopped, and request signaling must be performed to reallocate buffer and bandwidth resources • Most flow control techniques can manage link congestion • But not all schemes can (by themselves) reallocate all the resources required for retransmission when errors occur • either error correction or a scheme to handle reliable transfers must be implemented at a higher layer
- Page 1 and 2: Special Course in Computer Science:
- Page 3 and 4: Network-on-Chip (NoC) Why NoC OCP S
- Page 5 and 6: From simpler to more complex chips
- Page 7 and 8: Problems to solve • Cores that pe
- Page 9 and 10: Some driving forces • Technical I
- Page 11: NoC illustration
- Page 14 and 15: OCP standard for on-chip communicat
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- Page 26 and 27: Introduction • Network-on-chip (N
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- Page 40 and 41: Switching strategies • Two main m
- Page 42 and 43: Switching strategies • Allocating
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- Page 46 and 47: Routing algorithms • Static and d
- Page 48 and 49: Routing algorithms • Minimal and
- Page 52 and 53: ACK/NACK flow control scheme • wh
- Page 54 and 55: Clocking schemes • Fully synchron
- Page 56 and 57: NoC Architectures examples
- Page 58 and 59: HERMES • Developed at the Faculda
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- Page 70 and 71: Motivation • Increasingly harder
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Routing algorithms<br />
• Routing algorithm must ensure freedom from livelocks<br />
• livelocks are similar to deadlocks, except that states of the resources<br />
involved constantly change with regard to one another, without<br />
making any progress<br />
• occurs especially when dynamic (adaptive) routing is used<br />
• e.g. can occur in a deflective “hot potato” routing if a packet is bounced<br />
around over and over again between routers and never reaches its<br />
destination<br />
• livelocks can be avoided with simple priority rules<br />
• Routing algorithm must ensure freedom from starvation<br />
• under scenarios where certain packets are prioritized during routing,<br />
some of the low priority packets never reach their intended<br />
destination<br />
• can be avoided by using a fair routing algorithm, or reserving some<br />
bandwidth for low priority data packets
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