Traffic Engineering with MPLS for QoS Improvement by bestt571


More Info
									               International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: 10 No: 03         45

               Traffic Engineering with MPLS for QoS
                                    Prof. Dr. Adeel Akram, Adeel Ahmed
                              Department of Telecommunication Engineering
                      University of Engineering and Technology Taxila Pakistan 47040

                                                                  o   Yellow arrows is the traffic path from R2 to
There can be a lot of QoS parameters that can                         R3
improved in IP MPLS network Backbone such as                      o   Indigo arrows shows the traffic path from
bandwidth, CPU utilization, memory requirement,                       R1 to R3
resources distribution and database optimization of               o   Black arrow indicates the under utilization
each router in the backbone.                                          links
In this paper, we have optimized database of each
router by involving DR/BDR election on each                   With the implementation of MPLS network and
interface so that all involved routers use that               doing traffic engineering we can easily divide the
elected DR router as to communicate hello packets             network traffic over the whole network, thus making
instead of communicating with all routers and hence           effective utilization of available links throughout the
database size of each router will remain small and            network.
require less memory and CPU utilization over                  Net result will be cost saving and congestion
MPLS backbone. Simulation results have been                   removal on different nodes in the network by
verified using MRTG, Olive/Vmware using                       sensing and using the ‘under utilized’ links [2]
conventional IP, MPLS without TE and MPLS using               In a pure IP network, the shortest path to a
TE capability.                                                destination is chosen even when it becomes more
Keywords: MPLS, VPNs, GGSN, SGSN, IS-IS,                      congested. Meanwhile, in an IP network with MPLS
OSPF, IBGP, EBGP, RSVP, LDP, BGP, EBGP,                       Traffic Engineering IGPB routing, constraints such
DR/BDR. MRTG, PE, CE, P, MPBN                                 as the RSVP bandwidth of the traversed links can
                                                              also be considered, such that the shortest path with
    1. Introduction                                           available bandwidth will be chosen. MPLS Traffic
                                                              Engineering relies upon the use of TE extensions to
In current IP networks, packets are routed on the             OSPF or IS-IS and RSVP. Besides the constraint of
bases of destination address and a single metric              RSVP bandwidth, users can also define their own
like hop-count or delay. The drawback of this                 constraints by specifying link attributes and special
conventional routing is that this approach causes             requirements for tunnels to route (or not to route)
traffic to converge into the same link; as a result it        over links with certain attributes [3, 4]
became a reason for significant increase in
congestion and leaving the network in a state of as               2. MPLS Layer Description
an unbalanced network resource utilization
condition shown in Figure 1.1 [1]                             Before we discuss MPLS we must know about
                                                              different protocols features such as OSPF, ISIS,
                                                              IBGP, LDP and RSVP. In order to describe those
                                                              features we have taken real networks as an
                                                              example. Multiprotocol Label Switching (MPLS) is a
                                                              standards-approved technology for speeding up
                                                              network traffic flow [5] MPLS involves setting up a
                                                              specific path for a given sequence of packets,
                                                              identified by a label put in each packet, thus saving
                                                              the time needed for a router to look up the address
                                                              to the next node to forward the packet to. With
   Figure 1.1 Flow of packets using traditional IP            reference to the standard model for a network (the
                     routing [1]                              Open Systems Interconnection, or OSI model),
               International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: 10 No: 03                46

MPLS allows most packets to be forwarded at the                  Figure 3.1 Conventional SGSN/GGSN network
layer 2 (switching) level rather than at the layer 3                               diagram
(routing) level. In addition to moving traffic faster
overall, MPLS makes it easy to manage a network               OSPF Properties Used:
for quality of service (QoS). MPLS have the
capability of both Layer-2 and Layer-3 network as                 o   OSPF is link state protocol means that it
shown in the figure 2.1                                               will send update to its neighboring routers
                                                                      only when it changes it state.
                                                                  o   Adjancey States will be Down, Init, Attempt,
                                                                      2-Way, Exstart, Exchange, Loading, Full
                                                                  o   Reference BW is always 10^8
                                                                  o   OSPF metric is the cost and cost is
                                                                      inversely    proportional      to   interface

                                                                  Metric = reference BW/ interface BW

                                                              Router Configuration (OSPF) Example :

                                                              protocols {
                                                                       ospf {
                                                                                area {
                                                                                interface em3.0;
                                                                                interface em2.0;
Figure 2.1 OSI/MPLS Layers comparison                                           interface lo0.0;
    3. IP/MPLS Implementation:                                              }
MPLS advantages can be judged with the help of its            Similar configuration are implemented on all the
implementation or replacing conventional IP                   routers mentioned in Figure 3.1
network with MPLS network. We have implemented
MPLS network over existing SGSN-GGSN network                  3.2 MPLS Implementation over SGSN-GGSN
which was previously using traditional IP routing             network
scheme. Gateway GPRS serving node (GGSN)
                                                              During this implementation we have introduced 8
3.1 Conventional IP core on SGSN-GGSN                         core MPLS routers in MPLS backbone which are
network                                                       called as P (Provider) routers in the network.
                                                              Similarly each site contains two M120 routers which
The conventional IP core was running over serial              are called as Provider Edge routers (PE) in the
link (2 Mbps of each maximum capacity) between                MPLS Packet Backbone network (MPBN) network.
the 4 routers located at two different places. The            The purpose of two routers is to provide
links were using OSPF as routing protocol for traffic         redundancy in each site.
routing between the two different places as shown
in Figure 3.1 [4]                                             In above mentioned Figure 3.1 the four routers in
                                                              conventional IP network format now act as
                                                              Customer Edge routers (CE) and these are now
                                                              uplinked directly with P routers in MPBN BB.

                       Virtual Routingand forwarding
                                                              We have implemented IS-IS & IBGP between the 8
                     OAM Group
                                         Traffic Group
                                            vrf_gngp          main core routers of MPLS. OSPF is implemented
                       rd 102:1              rd 101:1
                                                              between PE and CE in MPBN Backbone as shown
                                                              in Figure 3.2
                   International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: 10 No: 03             47

                                                                                interface lo0.0 {
                                                                                   level 2 disable;
                                                                  Similarly configuration are implemented on all
                                                                  routers mentioned in Figure 3.2

                                                                  Router Configuration (IGPB) Example:

                                                                  protocols {
 Figure 3.2 Migrated network diagram on IP MPLS                              bgp {
                    back bone                                                  group internal {
                                                                                   type internal;
Please note that MPLS cannot be compared to IP                                     local-address;
as a separate entity because it works in conjunction                               neighbor;
with IP and IP's IGP routing protocols. MPLS gives                                 neighbor {
IP networks simple traffic engineering, the ability to                            }
transport Layer 3 (Network Layer) VPNs with                                     }
overlapping address spaces, and support for Layer                            }
2 pseudo wires. Thus routers with programmable                    ……………………………
CPUs can be implemented [5, 6]                                    Similar configurations are implemented on all
                                                                  routers mentioned in Figure 3.2
    •   explicitly configured hop by hop,
    •   dynamically routed by the IS-IS,IGPB                      Configuring MPLS Traffic Tunnel:
        algorithm, or Configured as a loose route
        that avoids a particular IP or that is partly             [edit protocol rsvp]
        explicit and partly dynamic. [7, 8]                       lab@RT-01# show
                                                                  interface all;
                                                                  interface fxp0.0 {
Router Configuration (IS-IS) Example :
// Make all IS-IS speaking interfaces as member of
                                                                  interface fe-0/0/1.0 {
family iso
                                                                  authentication-key "$9$MKZL7Vji.mT3"; #
         lo0 {
               unit 0 {
                 family inet {
                                                                  edit@RT-04# show protocols mpls
                                                                  interface so-0/1/0.100;
                 family iso {
                                                                  interface so-0/1/1.0;
                                                                  interface fe-0/0/1.0;
                                                                  interface fe-0/0/2.0;
                                                                  interface fe-0/0/3.0;
                                                                  Similar configurations are implemented on all
                                                                  routers mentioned in Figure 3.2
protocols {
              isis {                                                  4. Results:
                          interface em2.0 {
                       level 2 disable;                           By comparing & analyzing the data transfer graphs
                 }                                                obtained from the transfer of data across the two
                 interface em3.0 {                                networks there is a clear indication that MPLS
                    level 2 disable;                              network with Traffic Engineering has significantly
                                                                  improved the performance of the network.
               International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: 10 No: 03                 48

                                                              Delay jitter in conventional IP network can be seen
Data rate found much higher in case of IP/MPLS                in the following diagram which shows that due to
network as indicated by the following MRTG graphs             congestion jitter appears
in which we have interface traffic compared with
respect to time 24 hours. We have time sampled
every millisecond along x-axis and bits per second
along y axis. Input and output traffic of each
interface is mentioned in MRTG graphs

                                                               Figure 4.5 jitter rate using conventional IP network

                                                              Delay jitter in MPLS network without using its TE
                                                              capability is more or less similar to conventional IP
 Figure 4.1 Data rate using IP MPLS TE capability

Data rate through conventional IP network is much
less than MPLS based network

                                                               Figure 4.6 jitter rate using MPLS without using TE

                                                                  5. Conclusion:
Figure 4.2 Data rate using conventional IP network
                                                              In this paper, the simulated concepts behind
Data rate through MPLS network without using TE
                                                              conventional IP network and MPLS traffic
capability is more or less similar to conventional IP
                                                              engineering had been verified through various
                                                              analysis. The outcome of this paper was highly
                                                              predictable. Through simulation results on
                                                              (VMWare/Olive) and analysis, it was clearly proven
                                                              that IP networks only provide best effort service and
                                                              does not provide any form of resource assurance to
                                                              traffic flows or any resource guarantees to users.
                                                              By mixing different types of transport in the same
                                                              path of the IP network, it can cause network
     Figure 4.3 Data rate using MPLS without                  performance problems such as starvation and
               implementation of TE                           unfairness for certain traffic.
                                                              However, with proper MPLS TE applied to the
Similarly delay jitter in case of IP/MPLS found               network, the performance of the Network is
almost negligible                                             significantly improved by dividing traffic into
                                                              separate routes that can be engineered; adequate
                                                              resources to deliver a good quality of service are
                                                              achieved.     Therefore,      the  overall   network
                                                              performance is improved in terms of throughput,
                                                              network utilizations and packet loss rate.

                                                                  6. References:
    Figure 4.4 jitter rate using IP MPLS network              [1] M. K. Huerta, J. J. Padilla, X. Hesselbach,¡ R.
                                                              Fabregat, O. Ravelo “Buffer Capacity Allocation: A
                                                              method to QoS support on MPLS networks”
               International Journal of Electrical & Computer Sciences IJECS-IJENS Vol: 10 No: 03   49

presented at Tenth International Conference on
Computer Communications and Networks, 2007

[2] Ibrahiem El Emary, Sherif M. Gad and Ala'a A.
Al-Zo'bi “New IP QoS Architecture for Voice and
Data Convergence over DSL Lines” Presented at
World Applied Sciences Journal 4 IDOSI
Publications, 2008

[3] Victoria Fineberg “QoS Support in MPLS
Networks” presented at MPLS/Frame Relay
Alliance White Paper, May 2003.

[4] Anton Riedl, “Optimized Routing Adaptation in IP
Networks Utilizing OSPF and MPLS” International
Conference on Computer Communications and
Networks IETF RFC 2328, April 2008.

[5] Ali El Kamel and Habib Youssef “An RSVP-TE
approach for the End-to-End QoS provisioning
within MPLS Domains” RFC 4736 International
Conference on Computer Communications and
Networks, November 2009

[6] Jasmina Barakovic, Himzo Bajric, Amir
“Multimedia Traffic Analysis of MPLS and non-
MPLS Network” 48th International Symposium
ELMAR-2006, 07-09 June 2006, Zadar, Croatia.

[7] Yihan Li, Shivendra Panwar, C.J. (Charlie)
Liu“Performance Analysis of MPLS TE Queues for
QoS Routing” International Conference on
Computer Communications and Networks RFC
3031, 2009

[8]    Gajeongdong,        Yuseong-gu,       Daejeon,
“Multiprotocol label switching & Differential Services
as QoS solution” IEEE transactions on Networking
& Management Vol 12 issue 1, May 2007

To top