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American Journal of Engineering and Technology Research
Vol. 14, No. 1, 2014
RESEARCH ON MULTIPLY TRAFFIC TRANSMISSION EXPANSION IN
OPTICAL INTEGRATED SERVICES DIGITAL NETWORK
Wei Yang1, Mingyuan Wu1, Ting Yang2
1
School of Mechatronics Engineering, Henan University of Science and
Technology, Luoyang, Henan, China
2
School of Electrical Engineering and Automation, Tianjin University
Tianjin, China, [email protected]
Abstract. Optical transmission technology and fiber communication network are widely utilized
in the Metropolitan Area Network (MAN), such as telecommunication, electrical power system
communication, and smart transport communication. With more and more digital equipments
connected, the disadvantages of traditional SDH technique became obvious. Different from
traditional optical network, control plane is introduced into automatic switched optical network
(ASON) to manage traffic flow. Integrated services digital network (ISDN), based on ASON
technique, could supply a variety type of traffic and achieve effective transmission ability. This
paper studied the multi-cast service type in ISDN, and proposed a novel multiply traffic
transmission expansion (MTTE) algorithm. MTTE embed DiffServ model into Generalized
Multiprotocol Label Switching (GMPLS) and provide guarantee IP QoS (Quality of Service).
Moreover, congestion occurred at local node can be avoided. With computer simulation, it is
benefit to enhance networks’ utilization ratio and ensure high priority traffic transmitted with
low delay.
Keywords: Generalized Multiprotocol Label Switching, Quality of Service, Differentiated
Services, Integrated Services Digital Network.
Introduction
With the development of optical communication technology and fiber networks, various data
traffic flows can be efficiently loaded on optical communication system, such as integrated
services digital network. Moreover, the introduction of the optical control plane (CP) allowed the
simplification and automation of provisioning in ISDN networks. The ITU-T Automatic
Switched Optical Network (ASON) standard describes the set of CP components that are to be
used to manipulate transport network resources in order to provide the functionality of setting up,
maintaining, and releasing optical connections [1][2].
On the other hand, traditional service can not achieve the multi-QoS traffic flow. With the Best
effort service, traffic is transmitted as quickly as possible, but there is no guarantee as to
timeliness or actual delivery. Therefore, the Internet Engineering Task Force (IETF) has
proposed many service models and mechanisms to meet IP QoS. Notably among them there are
InterServ/RSVP (Resource Reservation Protocol) model, DiffServ model, MPLS/GMPLS,
Traffic Engineering (TE) and CBR. [3]
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In networks, one router relays traffics to another depending on hardware and software routing.
Hardware routing transmits packets, and software routing can achieve special function with
different routing strategy. Research new IP QoS algorithm to satisfy multi-traffic transmission
guarantying communication requirements becomes a hotspot.
Because of the complexity of the QoS requirements and network’s applications, such as smart
transport communication, telecommunication, and electrical power system communication, using
one technology alone can hardly reach the optimized schedule. By analyzing IP QoS models
(IntServ and DiffServ) and the GMPLS technologies, the paper presents a novel multiply traffic
transmission expansion (MTTE) algorithm, which can be applied in the optical control plane and
improve the ISDN performance with satisfy the QoS requirements of high priority flows.
The remainder of this paper is organized as follows. Section II proposed the relative work,
including two kinds of IP QoS models, IntServ and DiffServ, MPLS/GMPLS technology. The
MTTE is described in section III. And then it is analyzed and simulated in section IV, V. Section
VI concludes this paper.
Relation Works
A. InterServ Model. With IntServ model, the routing path must be set up firstly and the
resources should be reserved by Resource Reservation Protocol (RSVP). Then data flows cross
the area on the path and QoS requirements are achieved. But IntServ/RSVP model has its own
shortages: (1) The amount of state information increases proportionally with the number of
flows, which places a huge storage and processing overhead on the routers. (2) The requirement
for routers is high. All routers must implement RSVP and schedule packet. (3) There is no
scalability in the Internet core.
B. DiffServ Model. Because of the difficulty in implementing IntServ/RSVP model, DiffServ is
proposed by IETF and has been completely implemented in IPv6. DiffServ is significantly
different from IntServ. Only a limited number of service classes are handled in DiffServ rather
than all of the flows in InServ/RSVP. It is therefore more scalable.
DiffServ defines the DiffServ domain which is a subnet providing assured and premium
Differentiated Service [4]. The routers at the edge of the subnet are called Edge Routers (ER)
and others are Core Routers (CR). In the approach, packets are classified, policed, shaped, and
marked DiffServ Code Point (DSCP) by ER. These operations can not only insure the Per-Hop
Behaviors (PHB) according with the Traffic Conditioning Agreement (TCA), but also test the
velocity of traffic and reduce the extent of traffic’s outburst. DiffServ redefined the TC field of
IPv6 header with DSCP. In TC field, the last 2 bits are undefined and the first 6 bits store DSCP.
The first 3 bits define differentiated service classes and the following 3 bits define different loss
rate for each class. CR needs only to implement Behavior Aggregate (BA) classification and
forward traffic according with its PHB. It makes CR simple and forwards packets very fast.
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C. Transmitting and Switching Technique – MPLS/GMPLS. IntServ and DiffServ are
absolute technologies in network layer, which do not relate to the data link layer. However, the
network layer is not able to hold the network’s real state. Only the technologies based on the data
link layer can exactly grasp them.
MPLS/GMPLS is just the technology mapping traffics from network layer to data link layer,
which is an advanced forwarding scheme [5].
MPLS extends routing with path controlling. At the ingress LSRs of a MPLS-capable domain, IP
packets are classified and routed based on a combination of the information carried in the IP
header of the packets and the local routing information maintained by the Label Switched
Routers (LSRs). A MPLS header is then inserted for each packet. Figure 1 presents the
MPLS/GMPLS header and IPv6 header formation. Within the MPLS-capable domain, each LSR
will use the label as the index to find the next hop in the forwarding table. Before a packet leaves
the MPLS domain, its MPLS header is removed at the egress LSR. The paths between the
ingress LSRs and the egress LSRs are called Label Switched Paths (LSPs). In order to control
LSPs effectively, each LSP can be assigned one or more attributes based on different QoS
requirements.
GMPLS is an implementation of the CP that also has been developed by the IETF to facilitate
the establishment of LSPs, involving signaling, routing, and resource management functions and
protocols. GMPLS implements all functional entities necessary for controlling an ASON,
actually going beyond the pure optical domain and being capable of setting up LSPs in a variety
of data plane technologies.
Fig. 1 MPLS/GMPLS Header and IPv6 Header Format
Algorithm Description
A. Communication Networks Mathematical Model. With Graph theory, An optical
communication network, such as ISDN, based on DiffServ over MPLS VPN model is
represented as a connected, simple digraph, which is established by thousands of different logical
nodes/routers and edges. Each node has its own properties and exchanges data with its neighbor.
Finally, a connected, simple digraph G=(E,N,H) is established, where E={E1,E2}, E1 is the set
of edge logic nodes and E2 is the set of code ones, N is the set of links and H={H1,H2}, H1 is
the set of each router’s measurements and H2 is the set of each link’s measurements.
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With each router E={E1,E2}: H1={Hop+(E) ,Delaymax(E), Jitter(E), LossP(E)}, Hop+(E):
ein→eout is the increased hops that a data packet passes the router E, Delaymax(E): ein→eout is
the delay that a data packet experiences on the corresponding router E (the sum of queuing delay,
transmission delay, and propagation delay). Jitter(E) and LossP(E): ein→eout is the impulsion
and the probability of loss for a packet passing the router. With each link l (lN, and the
direction is E→E’+): H2={Ur(l),Metric+(l)}, Ur(l):E→E’+ is the maximum bandwidth provided
for applications; Metric+(l): E→E’+ is a measure of the utilization of this link’s resources.
In mathematic model, the state of router E’s queue can be transformed into the used bandwidth
of link l, which contents at the end k on router E. So QoS of the class j is:
QoSj(Ing,
LossP_maxj}
Eng)={BandW_minj,
Delay_maxj,Hop_maxj,
Metc_maxj,
Jitter_maxj,
(1)
The proposal of this model is to compute one or more LSPs (Label Switched Paths) for each
class of traffic, and to optimally configure these LSPs, in order to make full use of the network
resource, and effectively avoid network congestion.
B. Mathematical Model’s Engineering Mapping. The mathematical simplicity and modeling
are reasonable and can be mapped in practical engineering. We present analyses ISDN applying
in electric power system.
Electric power system, reliable and secure delivery of energy, is essential to modern society [6].
To reduce the greenhouse impact, and decrease the power energy cost, Smart Grids are proposed.
It is an advanced concept with a number of unique features compared to their precedents,
including early detection and self healing capabilities. Advanced metering infrastructure, reliable
bidirectional communication and life cycle management are the very important techniques in the
Smart Grid design.
Smart Grid system requires high speed sensing of data from all the sensors on the system within
a few power-cycles. With the development of electronic, communicate, and signal processing
techniques, more and more second equipments in substation automation system are connected in
to the electric power communication networks, which include relay protections, signal system,
measurement instruments, and automatic equipments,. The main equipments, transmission and
distribution circuits can be completely monitored, measured and controlled. Integrated services
digital networks with optical communication are designed to achieve the multiply types of
traffic.
The Communications Networks and Systems in Substations Protocol, IEC61850 [7], is just the
new networking approach for substation automation system. It was designed for higher-speed
networks that can carry more data. More capacity and speed enables automated control actions
that are initiated by computers in the substation rather than by a human at a distant central site.
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The protocol specifies how power system devices should organize data in a consistent way for all
types and brands of devices, and related services.
It also standardizes data names for logical devices containing logical nodes for automatic control,
metering and measurement, supervisory control, generic functions, interfacing/archiving,
protection, sensors, instrument transformers, switchgear, power transformers and other
equipment. IEC61850 also creates a comprehensive set of services for logical devices and nodes,
implements them within standard protocols and hardware, and defines a process bus.
Employing IEC61850, the abstraction of data items/objects and services provided are
independent of underlying protocols. Then, abstract data model is easily mapped to a specific
protocol stack based on MMS (ISO/IEC 9506), Ethernet or the integrated services digital
networks.
C. MTTE Algorithm Flow. Reference [8] proved that satisfying all of QoS has been NPComplete. We use greedy strategic to optimize the load balance. The algorithm firstly analyzes
the character of networks’ existing state from TED (Traffic Engineering Database) and
determinants networks’ type, then computes LSPs to achieve each class’s IP QoS by different
united object functions and MPLS over DiffServ technology.
Link Utilization Ratio:
Ur(li )  [(1 -   k )ToBw(li ) 
klsp
 usBw (l )] / ToBw(l )
jlsp
j
i
i
(2)
Where αk is the bandwidth retained ratio for the class service k; usBwj(li) is the used bandwidth
of the class j in link li.
Load balancing degree (G):
Ur(li ) 2
Ur(li ) 2
(3)
 (G)  
 (
) 100%
N
lN
lN
N
Here we regard the load balance degree (G) as the standard of rationality of traffic load
distribution.
n
[Ur]k  （Ur(li ) / n)
[Ur]
j
i 1
For collocation k, 
is less than
, where j≠k, it defined collocation k is
better than collocation j, and it is a load-unbalancing networks with collocation k.
How to execute MTTE in routers and the basic steps of MTTE are shown in Figure 2.
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American Journal of Engineering and Technology Research
In edge LSRk:
Vol. 14, No. 1, 2014
In core LSRj:
do{
Define the class for Traffici by QoS (Ingj, Engj ) ;
MPLS(Lab)The class of Traffici;
If (Lab = = AF)
Configure the different loss-packets probability to
MPLS(EXP);
}which ( {Traffic1,…, Traffici} is end );
if ( Classk = = EF || Classk = = BF )
LSRj → LSRj+1 by MPLS head;
else{
if (Quk  Routj is congestion)
// Quk:
queue for Classk
Losing packets based on the MPLS (EXP)
defined ;
else
LSRj → LSRj+1 by MPLS head ; }
do{
If (the traffic class is EF serive type)
Define Lsp_Obj[ ] = {Hop, Ur, Metric } ;
Else if (the traffic class is AF serive type)
Define Lsp_Obj[ ] = {Ur, Hop, Metric } ;
Else // the traffic class is BF serive type
Define Lsp_Obj[ ] = { Metric, Ur, Hop} ;
Allocate MPLS head for each LSP ; }
} while ( ClassEF = { … } is end ) ;
Fig. 2 Pseudo Code MTTE
Algorithm Analysis
From the stated above all, we can get the conclusion that the MTTE algorithm has some
advantages.
Firstly, MTTE algorithm can be compatibly applied in optical ISDN. Border routers in networks
region classify each of traffic by its QoSj(Ing, Eng). Then MTTE algorithm sets up LSP by
different types. It can avoid the Micro-flow “N2”problem in traditional routing, where N is the
number of boundary routers. So the algorithm is scalable.
Core routers forward packet only by examining its MPLS header (Because Border routers have
set up LSPs, Core routers merely examine LAB fields to transmit). Moreover, if there is a
bottleneck area, the core routers in this area can distinguish the loss-packets level of each class
by merely examining the EXP field, and then routers can perform different loss-strategy. All
these insures MTTE algorithm to fast classify and forward packets. Moreover, because the
DiffServ system is great expansible, MTTE can be suit for both local and metropolitan area
electric power communication network. It is only necessary to configure different SAS data to
different DiffServ Code Point (DSCP).
Secondly, employing MPLS technology between link layer and network layer, TED can get
more accurate link-state information, It avoids the traditional algorithms’ shortage that out-ofdate information makes the fail connect[9][10].
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Considering an initial network, MTTE algorithm configures the traffic from high priority to low
one, which avoids the divested problem. On the other hand, for a network existing running
traffic, algorithm can analyze the utilized resources. When some traffic is divested by higher
priority traffic, they will be ascribed to the armed traffic-cluster. This strategy can decrease the
networks’ instability from more re-routing. MTTE algorithm set up LSPs with united object
functions, which is made by the state of the resource utilization, load distributed in networks, and
the different QoS requirements in different service classes. It produces effective projects for the
problem of satisfying Multi-requirement in one routing count, which is NP-Complete. And
centralized control is applied to the transmission paths of different service types in the algorithm.
Simulation and Performance
A. Simulation Environment. The simulation networks’ topology is shown in Figure.3, there are
ten routers, router 4 and 5 are core routers and others are edge routers. 38 optical cables connect
the routers, where the number on the link is maximum bandwidth. Because of the space, other
restrictions don’t be shown in the figure.
Now, there are 200 pieces of traffic to be configured by two kinds of algorithm, one is the OSPF
algorithm, the other is the MTTE algorithm. The rate of network balance and each links’
bandwidth utilization ratio are counted and analyzed.
Router 1
Router 2
740M
610M
Router 3
800M
Router 4
800M
830M
610M
650M
860M
Router 6
750M
Router 7
Router 5
860M
500M
800M
Router 8
620M
510M
870M
800M
810M
600M
870M
Router 9
Router 10
Fig. 3 Topology of Networks’ Model
B. Simulation Results. Imaging the network’s resource after the routing in Figure.4,5, we can
found, using OSPF algorithm, the load was unbalanced in the whole networks (=14.25%). But
MTTE algorithm configured the same set of traffic, the resource of network was fully used and
avoided the possibility of congestion. The average of links’ utilization ratio is about 50%
(=7.82%). Moreover, the hop-limited strategy makes LSP obey the strict Hop constraint in
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some special classes of service. Thus, the same as the section of algorithm analysis, MTTE
algorithm is able to make the resource used more balanceable.
Table 1 Links’ Bandwidth Utilization Ratio Balancing Degree 
Service Type
Premium Forwarding
Assured Forwarding
Best Effort Forwarding
Total Service
OSPF Collocation 
11.49%
7.18%
4.99%
14.25%
0.6
0.6
Premium Forwarding
Premium Forwarding
Assured Forwarding
0.5
Assured Forwarding
0.5
Best Effort Forwarding
0.4
Utilization Ratio %
Utilization Ratio %
MTTE Collocation 
5.52%
5.46%
2.67%
7.82%
0.3
0.2
0.1
Best Effort Forwarding
0.4
0.3
0.2
0.1
0
1
3
5
7
9
0
11 13 15 17 19 21 23 25 27 29 31 33 35 37
1
Optical Cables
3
5
7
9
11 13 15 17 19 21 23 25 27 29 31 33 35 37
Optical Cables
Fig. 4 Utilizations Ratio of Network’s
Resource by OSPF
Fig. 5 Utilizations Ratio of Network’s
Resource by MTTE
Conclusions
While energy remains a major component of economic growth, power industries, government
and national university have developed established Smart Grid with low-carbon generation
technologies. To achieve the bidirectional communication requirements in Smart Grid, MTTE
algorithm is proposed and evaluated in this paper. It can make networks provide guarantee IP
QoS service and fast forward packets. With the algorithm analysis and simulation, the resource
of network is fully used and avoids the possibility of congestion by MTTE. And the fluctuation
of each links’ Ur is balance, which the mean square deviation is decreased 45.6 %.
Acknowledgement
This work was sponsored by “The Henan Provincial Key Lab for Machinery Design and
Transmission System”, “Henan high Educational open key lab for Advanced manufacturing
Technology”, and “The State Key Lab of Tribology”. This work was also sponsored by the
National Natural Science Foundation of China No.60702037, 61172014, Natural Science
Foundation of Tianjin No.09JCYBJC00800. Corresponding author is Ting Yang and his email is
[email protected].
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