Design and implementation of secured agent based NoC using shortest path routing algorithm

International Journal of Electrical and Computer Engineering (IJECE)
Vol. 9, No. 2, April 2019, pp. 950~959
ISSN: 2088-8708, DOI: 10.11591/ijece.v9i2.pp950-959  950
Journal homepage: http://iaescore.com/journals/index.php/IJECE
Design and implementation of secured agent based noc using
shortest path routing algorithm
Kendaganna Swamy S, Anand Jatti, Uma B. V.
Department of Electrical & Instumentation Engg, R.V College of Engineering, Bangalore, India
Article Info ABSTRACT
Article history:
Received Jul 9, 2018
Revised Oct 10, 2018
Accepted Nov 19, 2018
Network on chip (NoC) is a scalable interconnection architecture for every
increasing communication demand between many processing cores in system
on chip design. Reliability aspects are becoming an important issue in fault
tolerant architecture. Hence there is a demand for fault tolerant Agent
architecture with suitable routing algorithm which plays a vital role in order
to enhance the NoC performance. The proposed fault tolerant Agent based
NoC method is used to enhance the reliability and performance of the
Multiprocessor System on Chip (MPSoC) design against faulty links and
nodes. These agents are placed in hierarchical manner to collect, process,
classify and distribute different fault information related to the faulty links
and nodes of the network. This fault information is used for further packet
routing in the network with the help of shortest path routing algorithm. In
addition to this the agent will provide the security for the node by setting
firewall, which then decides whether the packet has to be processed or not.
This intern provides high performance, low latency NoC by avoiding
deadlock and live lock with low area overhead.
Keywords:
Congestion
Fault tolerant
Network on chip
Permanent fault
Random arbiter
Routing algorithm
Security
Shortest path routing Copyright © 2019 Institute of Advanced Engineering and Science.
All rights reserved.
Corresponding Author:
Kendaganna Swamy S,
Department of Electrical & Instumentation Engg,
R.V College of Engineering, Bangalore, India.
Email: kendagannaswamys@rvce.edu.in
1. INTRODUCTION
As a feature size of the transistor scaling down, the number of transistor on a single die increases
whose result improves the number of IP cores on the SoC. As number of IP cores increases on SoC the
networking becomes a bottleneck issue. The conventional crossbar and switches will not be able to support
the communication between more number of IP core based SoC because of their performance degradation.
In order to improve the communication performance on SoC a new method has been introduced that is
Network on Chip. Such NoC is capable to improve the networking performance on MPSoC [1] when
compared to conventional method if and only if network is fault free.
If there is any local fault on the network, it may be in router or link or Processing Element (PE) or in
Network Interface (NI) element. Due to this fault [2], [3], there may be a chance for the packet to enter into
the deadlock or live lock or packet loss. Then packet has to remap once again which leads to performance
degradation. These local faults [4] may occur during the fabrication process or down the length of year of
usage. Hence there is a demand to create awareness of local fault in NoC before mapping any packet into any
of the node in the network [5]. Hence there should be an intelligence unit on NoC to be aware about local
fault before mapping any packet.
The Background work in [6-8] the author addresses the local fault awareness using fault tolerant
routing algorithm and it is software in nature which may lead to long routing path hence there is a more
packet latency and throughput degradation [9]. In [10]-[12] the author introduces the hardware based
hierarchical agents on the NoC in order to gather and classify the fault information and transfer that message

Int J Elec & Comp Eng ISSN: 2088-8708 
Design and implementation of secured agent based noc using shortest path… (Kendaganna Swamy S)
951
to upper layers [13]. Such agent based NoC method uses the odd even based routing algorithm. This method
will improve the network performance with an area overhead and these agents are unsecure in nature [14].
Hence there is research scope to enhance the feature of fault tolerant agents.
1.1. The problem
The significant research problems are as follows:
a. Existing agent based NoC systems focused only an XY routing algorithm.
b. Conventional research towards fault tolerance doesn‟t emphasize on the scalability while evolving up
with fault tolerant protocol over network design.
c. Although existing studies have worked on fault identification but there are less number of studies
towards classifying the faults existing over the networks.
d. None of the existing studies towards NoC has highlighted any design issues with its processing
elements that offer latent faults in any network architecture.
e. The mechanism of formulating the decision in ensuring better performance of fault tolerance network is
not clearly defined in any existing studies.
Therefore, the problem statement of the proposed study can be stated as “Developing a cost effective
modeling to encapsule comprehensive network faults with equivalent focus on packet-level controlling
mechanism in chip architecture with different routing algorithm is computationally challenging.”
1.2. The proposed solution
The prime aim of the proposed system agents are not only fault and congestion information provider
but also takes the decision whether packet has to pass or not to the Processing Element by setting the firewall.
Such secured agents will give two benefits such as placing the firewall on the chip is safer from the hackers
compare to off chip firewall. Second is, if the specific packets can be able to execute only through the
specific PE that time by securing such node we can overcome the waiting of highest priority packet looking
for the specific PE and overcome the live lock situation [15]. In the proposed design in order to route the
packets, shortest path routing algorithm is used which will improve the network performance with less area
overhead as compare to [16]-[20] the proposed stsem is described in detail in Section 2.
2. PROPOSED HIERARCHICAL AGENTS BASED MONITORING SYSTEM
The performance of NoC based multiprocessor system on chip depends on the packet switching and
processing rate on the network. The network has fault or congestion because of a faulty link or a router or a
PE which may occurs in manufacturing or in a operational phase. If the upper layer is not aware of such local
fault and congestion information then the packet enters into the dead lock and live lock situation which leads
to performance degradation. Then the proposed agents need to be placed in hierarchical manner as shown in
Figure 1. These agents will collect and classify the local fault [21], [17] and congestion information and send
them to the upper layer before mapping any packet into the node from the application layer. In addition to
this the proposed agent provides security to decide whether the received packet as to pass or not to the
processing element by setting the firewall.
Application Layer
Platform Level
Cluster Separation
Module
Cluster Agent Level
Cell Agent Level
Figure 1. Proposed hierarchical agent monitoring system flow

 ISSN: 2088-8708
Int J Elec & Comp Eng, Vol. 9, No. 2, April 2019 : 950 - 959
952
The proposed hierarchical agent system has five layers namely application layer, platform level,
cluster separation module, cluster agent and the cell agent. The platform level will receive the packet from
the application layer and try to produce the error free packet to the network layer by considering all network
erroneous scenarios [22] Cluster separation module decides the received packet belongs to which cluster
under N number of clusters. These cluster agents have N number of cell agents. Cluster agent will collect
fault information from the cell or node agents and update to the upper layer. The node or cell agent dedicated
to one node will collect, accumulate and distribute the fault and the congestion information of its own node
and neighboring node by updating the local fault register [LFR] and regional fault register
[RFR] respectively.
SPRA Module
R1….R16
Figure 2. 4x4 hierarchical agent based NoC
A 4x4 hierarchical agent based NoC is as shown in Figure 2, which consist of PE, router [23], NI
and the agents. All the agents are connected bidirectional in order to perform pear to pear communication and
there is a one bit information exchange between the agents to update the RFR. These agents are connected to
router network [24]. The packets form the upper layer enters into the router via cell agent in order to check
the security parameters which will be elaborated in the next section. The base line data communication takes
place between the routers in the network. In addition to this, the SPRA module is added to the network to
perform packet routing using shortest path routing algorithm [16]. The SPRA module is connected to each
and every node of the network.

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3. PROPOSED SECURED CELL AGENT DESIGN
The proposed cell agent is as shown in Figure 3 which will perform the following tasks: fault detection,
security, session monitoring and congestion detection hence the proposed design called as secured agent.
RAM
(16x6 Bytes)
Bypass
Register
Session
Monitoring
Config
Register
Control
Packet
N S E W Node PE U U
NE U U UNW NS NN U
Regional Fault Register (RFR)
Local Fault Register (LFR)
Packet
Processing
Security
Bypass or neglect the audio or
video contained packets
Count Up/Down (31:0)
Figure 3. Proposed cell agent design
3.1. Fault information classification
The network fault information classification is useful for the router to perform the routing process.
The fault detection circuitry in the agent will provide the appropriate signals. These signals provide the faulty
component information such as links, router and processing element. The cell agent accumulates,
manage and distribute the fault information of its own components with the help of LFR and update the
neighboring node faults with the help RFR.
N
0
S
0
E
0
W
0
PE
0
Node
0
EN
0
NN
0
SN
0
NN
0
RFR (Regional Fault Register)
LFR
(Local Fault Register)
N1
N
0
S
0
E
0
W
0
PE
0
Node
0
EN
0
NN
0
SN
0
NN
0
LFR
N2
N
0
S
0
E
0
W
0
PE
1
Node
0
EN
0
NN
0
SN
0
NN
0
LFR
N3
Figure 4. Fault information exchange between the agents
Figure 4 shows that how the cell agents update the fault information between the neighboring cell
agents. Assume N2 is the current node; its LFR gets updated based on its own component faulty status of its
PE, NI and the router. The RFR gets update based on faulty status received from the E, W, N and south side
neighboring agents. Assume Node3 PE is faulty, then the N3 LFR PE bit changes from status „0‟ to „1‟ this
faulty status gets updated in the neighboring agents RFR. The N2 is the neighbor of N3, the N2 RFR east
Node [EN] bit status changes from 0 to 1 to indicate east side node [N3] is faulty. This indicates that the east
side node is unhealthy and the packet from N2 will be routed towards south side rather than east side by
considering the RFR status to reach the destination of bottom right side of the node in the network.
The congestion information or the fault information is determined by the agents with the help of encoding
and decoding process.
3.2. Agent security
This cell agent will provide the security to the processing element using config register and control
packet stage. Config register is used for source port configuration (using lookup table concept) in order to
block the unwanted and unrelated packets to give security (like blocking the website or virus packets).

 ISSN: 2088-8708
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Control packet will get the authorized packet information from the config register and decides whether
packet must be passed or not to the processing element. In general, people can hack the secured firewall,
but in the proposed design, some of the port addresses are itself blocked in the hardware ( i.e inside the chip),
which avoids the intruder by hacking the firewall. The cell agent will ignore or bypass some of the packets,
if those packets contain video or audio related data using bypass register. The agents will also monitor the
maximum sessions per node using session monitoring stage. This session monitoring stage will take care of
start session and close session (limited to 0 - 31 sessions) after performing the task.
4. SHORTEST PATH ROUTING ALGORITHM
In the proposed system in order to rote the packet on the network, shortest pate routing algorithm
(SPRA) is implemented. This SPRA module is connected to each and every node of the network and
exchanges the one bit information bidirectional as shown in Figure 2. The SPRA will assign the weightage to
each and every node from 0 to 7; this weightage assignment indicates how busy the node is. If the weightage
assigned to the node is 7 means, the node is highly busy or if the weightage assigned to node is 0 means,
the node is idle. The SPRA module assigns two registers for each and every node, one is permanent
weightage assignment register and another one is temporary weightage assignment register. The value of
temp weightage register keeps on updating for each and every movement of the packet where as the
permanent weightage register will never change its value. The SPRA module will route the packet on the
network based on the weightage. The working flow of SPRA is as shown in Figure 5.
Start
Take request and
generate pass „1‟
Take new request
weight age and add
with existing
Compare the shortest
path
Generate the
corresponding pass
New Request
Figure 5. SPRA flow chart
For example if the packet generated in node1 as to reach Node16 using SPRA module, initially node
1 sends the request to SPRA module and SPARA module will take the request and check the weightage
status on its internal database and generate the one bit grant information to node1. Then it will check the
shortest path based on weightage like node1 can move ether move to node 5 or Node2 which are its
neighboring nodes respectively. The SPRA will add the node 1 weightage with Node2 weightage and update
the node2 temp weightage register value to new weightage value (i.e. 1+2 = 3). Similarly SPRA will add
node1 weightage with Node5 and update the node5 temp weightage register value to new weightage value
(i.e. 1+4 = 5). Then SPARA will compare both the weightage value and find the shortest path. Then SPAR
will generate the corresponding pass, it means that the packet will be sent from node1 to node2 side because
this path is having less weightage compare to node5 side. Ones it reaches the ndoe2 the proposed router will
crosscheck the destination location using destination bits on the packet, if this matches, it will stop the

955
routing process else further routing process takes place by generating the new request from node2 and it will
be continue till the packet reaches node16 (destination node). Figure 6 shows the shortest path direction from
node 1 to 16 with updated weightage assignment. The updated weightage on temp register is as shown in
brackets in the Figure 6 and the original weightage assigned in the register will not be affected by the
new value.
N1 N5 N9 N13
N2 N6 N10 N14
N3 N7 N11 N15
4 1 4
S
1
2
(3) (5) (7) (9)
2 2 2
3 3 3 3
N4 N8 N12 N16
4 1 4 1
(12)
(13)
D
Figure 6. Shows the shortest path direction from node 1 to 16
The Figure 7 shows the simulated waveform with respect the network configuration in Figure 6.
The packet moving path N1-N2-N6-N10-N14-N15-N16. In the waveform data enters into the N1 from its
own PE and virtually the data is sent out in all the direction first then actual packet is sent out based on the
decision of the SPRA module and finally it will send the packet data out to south (PoS) from node1 and
data_in to Node2 of north side i.e PinN based on weightage calculation. This will continues till the packet
reaches the destination node16.
Figure 7. Shows the simulated waveform

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5. IMPLEMENTATION AND PERFORMANCE EVALUATION
The proposed secured agent based NoC using shortest path routing algorithm is designed using HDL
code and simulated using Xilinx ISE 14.2 tool with modelsim 6.3f respectively.
Figure 8. 4x4 NoC implementation result
The proposed design synthesized and implemented on VERTX – 5 FPGA (XC5VFX70T) Kit,
which uses is 45nm technology with 100 MHz Operating frequency. Figure 8 shows the waveform recorded
at the output of the FPGA kit.
Figure 9. Average packet latency
The performance of the proposed system is compared with the existing method. Figure 9 shows the
comparison of average packet latency with existing system. In [5] it does not have any means to reliably send
all the packets to their destination in the faulty situation, there may be chance of packet entering in to
deadlock in the faulty node. Then packet will be resent from the top level, which leads to performance
degradation by increasing latency. The proposed system has prior knowledge of all the faulty links and
nodes. Hence the packet will reach the healthy node with a reliable time as compare to existing agent based

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system. The proposed system graph has high performance with saturation point compare to existing
system [14]. In the graph, proposed method saturation point is high i.e packet injection rate will be more and
it will reach the destination with a less number of clock cycles. From the graph existing method input packet
data rate lies between 0.25 and 0.3 by taking 100 clock cycles. The proposed method takes 77 clock cycles to
achieve the same data rate. Hence in the latency graph the line one which has higher saturation point with a
wider slanting have better performance hence proposed system have higher performance compare to [14].
Figure 10. Throughput of the proposed system
Figure 10 shows the throughput of the proposed system. The proposed system takes care of
receiving error free packets from the platform level itself hence packet remapping can be avoided and also
proposed system have prior knowledge of all faulty links and nodes which will give higher throughput under
different fault conditions and in the existing agent based system [14] author haven‟t discussed on throughput.
Table 1 shows the proposed system hardware utilization summary with gate count and the simulated
operating frequency was found to be 260.132 MHz with 3.927 delay path in the operation. The value of the
set-up time was observed as 2.022ns whereas that of the hold-time was 3.711ns. Both set-up time and hold-
time are slack values and do not result in time violation.
Table 1. Proposed design area utilization summary
The proposed agent based NoC system using shortest-path-Algorithm is compared with previous
similar NoC systems like RAFT [5] and traditional agent based NoC [14] in Table 2 to validate hardware
utilization improvements by 51.82 %, 55.50% and 55.50 % respectively. In the Hierarchical cell agent using
shortest-path, the routing process is controlled using Shortest Path Data Pass (SPDP) unit, which generates
the pass signal to each node that allows the shortest route to be followed. In routing, based on Pass signal, the
packet will traverse in east, west, south and north direction along with local output. In this module there is no
arbitration and packet will not traverse as per XY algorithm [14]. Because of these reasons, Hierarchical Cell
Agent using shortest-path consumes lesser area than Hierarchical Cell Agent using XY algorithm.

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Table 2. Agent based NoC system using shortest-path-Algorithm is compared with previous similar NoC
systems
Routing Method Area utilization (Gate Count)
for 5 Port
Area Overhead Comparison
(%) of RAFT[5]
Area Overhead Comparison
(%) of Agent based NoC [14]
RAFT[5] 39355 NA NA
Agent-based Routing[11] 41574 5.6 NA
Proposed agent based NOC
system using shortest-path-
Algorithm
17510 No Area Overhead No Area Overhead
Proposed agent based NOC system using shortest-path-Algorithm
Area reduced % compare to exisiting NoC system.
55.50% 55.50%
6. CONCLUSION
The proposed secured agent based on chip system design using shortest path algorithm have
hierarchical Agents. These agents secure the node by providing security and healthy status of the node to
upper layer. This healthy status information helps the upper layer to map the packet into healthy node.
This improves the performance by avoiding packet remapping and reduces the packet latency against faulty
links and nodes. In addition to this, the agent will provide the security to PE which avoids the unrelated and
unwanted packet for the dedicated PE. This intern overcomes the live lock situation of the high priority
packet. From the simulation and synthesized result, the proposed design provides better performance
compare to existing method using shortest path routing algorithm with less hardware overhead.
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BIOGRAPHIES OF AUTHORS
Prof. Kendaganna Swamy. S, Assistant Professor Department of Electronics and Instrumentation
engineering, R.V College of engineering, Bangalore. He is having 6yrs of teaching experience and
2 years of industry; Area of interest VLSI design, FPGA and NoC. He is published 19 papers along
with one national level patent published.
Dr. Uma B.V., working as Professor & Head in Department of electronics and communication
engineering, R.V College of engineering, Bangalore. She is having 25yrs of teaching experience,
Area of interest VHDL, VLSI design, Digital Electronics Circuits, Synthesis and optimization of
digital circuits, CAD tools for VLSI, CMOS VLSI design. She is published 48 papers.
Dr. Anand Jatti, working as an Associate Professor Department of electronics and
instrumentation engineering, R.V College of engineering, Bangalore. He is having 14yrs of
teaching experience; Area of interest image processing, signal processing and VLSI. He is
published 23 papers.

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