B
NI
NI
Request
Request
s 1
A
C
R
R
Response
Response
Request
Response
Request
Response
NI
NI
m 1
m 2
s 2
43
Interconnection Networks in Network-on-Chip
Figure 2.23
Solutions to message-dependent deadlock.
Having virtual instead of physical networks mitigates the aforementioned
problem as shown in Figure 2.23. However, the router complexity increases
as it must forward messages considering the message type. Virtual circuits
represent the extreme case of strict ordering as every connection has its own
logical network. This way of implementing unconditional delivery is found
in the guaranteed service networks of Æthereal (Radulescu et al. 2005) and
Nostrum (Millberg et al. 2004).
2.5 Flow Control Protocol
Flow control protocol determines how packets traverse through the network and
reach from source to destination. It also supports error control scheme either at
an end-to-end level or at a switch-to-switch level in the presence of transmission
error. For the end-to-end case, a standard flow control protocol is credit based.
In a credit-based flow control, an upstream node keeps count of data transfers.
Available free slots are termed as credits. Once the transmitted data packet is
either consumed in the receiver NI or further transmitted to the core, a credit is
sent back. Æthereal (Radulescu et al. 2005), SPIN (Guerrier and Greiner 2000),
and QoS architecture and design process for network-on-chip (QNOC) (Bolotin
et al. 2004) use the end-to-end credit-based flow control technique.
Murali et al. (2005) reported that the average packet latency is higher in
an end-to-end flow control compared to a switch-to-switch flow control.
The later scheme can further be classified as flit level (ssf) and packet level (ssp).
NI
NI
Request
Request
s 1
A
C
R
R
Response
Response
Request
Response
Request
Response
NI
NI
m 1
m 2
s 2
43
Interconnection Networks in Network-on-Chip
Figure 2.23
Solutions to message-dependent deadlock.
Having virtual instead of physical networks mitigates the aforementioned
problem as shown in Figure 2.23. However, the router complexity increases
as it must forward messages considering the message type. Virtual circuits
represent the extreme case of strict ordering as every connection has its own
logical network. This way of implementing unconditional delivery is found
in the guaranteed service networks of Æthereal (Radulescu et al. 2005) and
Nostrum (Millberg et al. 2004).
2.5 Flow Control Protocol
Flow control protocol determines how packets traverse through the network and
reach from source to destination. It also supports error control scheme either at
an end-to-end level or at a switch-to-switch level in the presence of transmission
error. For the end-to-end case, a standard flow control protocol is credit based.
In a credit-based flow control, an upstream node keeps count of data transfers.
Available free slots are termed as credits. Once the transmitted data packet is
either consumed in the receiver NI or further transmitted to the core, a credit is
sent back. Æthereal (Radulescu et al. 2005), SPIN (Guerrier and Greiner 2000),
and QoS architecture and design process for network-on-chip (QNOC) (Bolotin
et al. 2004) use the end-to-end credit-based flow control technique.
Murali et al. (2005) reported that the average packet latency is higher in
an end-to-end flow control compared to a switch-to-switch flow control.
The later scheme can further be classified as flit level (ssf) and packet level (ssp).