Point to Point Label Switching Protocol for Optical Access Networks

8/2/2019 Point to Point Label Switching Protocol for Optical Access Networks

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Point to Point Label Switching Protocol forOptical Access Networks

Jungjoon Lee, Junkyun Choi

Abstnrrt-This paper concentrates on the provisioning ofservicesusing point-to-point protocol (PPP) and label switchingscheme in IP over DWDM access networks. For the reason ofusefulnessof PPP and the efficiencyof label switching technique inaccess networks, I propose three -solutions for end-toend orend-to-provider communication on the optical access networks.Three solution candidates for access networks are 10 Gigabit

Ethernet network, Resilient Packet Ring (RPR) network, andPassive optical network (PON).These Topologies have their ownadvantages. So this article presents how we can use thesearchitectures properly in the access networks with the PPP andlabel switching techniques over a DWDM layer.

Index Terms-Access networks, IP over DWDM, Labelswitching, PPP

I. INTRODUCTIONN wadays Internet access architectures for residents,SOH0 (Small Office Home Office) and local areanetwork subscribers are being developed largely with xDSL,Fast Ethemet, and furthermore Gigabit Ethemet. And they canaccess a network with the data rate fiom 100 Mbps to 1Gbps. Inaddition, the backbone area networkcansupportup to fewTbpsby using DWDM technology[l].But the problem is the accessarea that connect customer premises network to Internetbackbone network. Still now, the access network only useT1 -T3 line as shown in Fig. 1.Therefore upgrading this area is veryurgent problem to figure the problem out bottleneck of accessInternet or Service providers.

So we need a certain optimized structure and a adjustprotocol to expropriate the large number of subscribers inaccess networks without degradation of speed. This articlesuggest the proper structure is the combination of Ethernetpacket Ring and Passive Optical Network (PON), and theproper protocol for that network is a LABELING protocolscheme and PPP extensions by using IPPPPDWDMarchitecture.

This work was supported in part by the Electronics andTelecommunications Research Institute (ETRl), Korea Telecom,and KOSEF.Jungioon Lee is with the School of Engineering, Information andCommunications University, TAEJON, KOREA (telephone: 82-4 2-86 6-62 31,e-&: [email protected]).Jun kyun Choi is With the School of Engineering, Information andCommunications University,TAEJON,KOREA (telephone: 8 242 -866 -6 122,e-mail:[email protected]).

UserI A N(1OOMbps-1Gbps)

I_Access Area Back Bone (Tbps)(T1 - T3 )Congestion !

Fig. 1 Access area bottleneck

II. IP/ PPP OVER DWDMThe ultimate solution would be to take IP directly over

DWDM. This will bring about scalability and cost-effectiveness.Now we have industry products that actually implementIP overDWDM already. In effect we are totally eliminating ATM andSONET layers from the networks. The proponents of IP overDWDM say that SONETs reliability is due to a lot ofredundancy. This overkill prevents the network from using alarge portion of its resources.

With the developmentof rbium-doped fiber amplifiers mostsystems that use IF over DWDM using SONET fiames haveremoved the SONET multiplexers. Furthermore, major carrierssuch as AT&T, Sprint, Enron, Frontier, Canarie, have all begunto realize the huge economic potential of IP over DWDM andthere is no onger any skepticism about hi s technology[Fig. 2.1.

To do this, we need to insert a certain protocol that makes itpossible forIP to be carried over DWDM networks between anIP and a DWDM layers.

Point-to-point Protocol (PPP), which is akind of solution thathas customers access an Intemet service, is a well-knownservice in circuit-switched telephone networks. But it is alsoconsidered a good choice for the delivery of broadband servicesin packet networks. The reason why we want to employ PPPover IP over DWDM Network is i t satisfies easily most of herequirements associated with remote connectivity to an NSP,such as IP address assignment, security, and AAA(authentication, authorization and accounting) functions. Inaddition, since ISPs and corporations are familiar with PPPbased connectivity, easy migration fiom existing ISPinfrastructure is expected, if the protocol is light (efficient). Butso far there is little activity in this area.

For the reasonofabove statements, the link protocol betweenan P and a DWDM layers should be similar to PPP and have theproperties ofPPP.

IEEE CatalogueNo. 01CH37239 2570-7803-7101-1/01/$10.000 2001 IEEE.


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reservation. Label switching can permit the actual IP header in apacket to be encmted since all that must be available to the_LSR is the label itself. In this way the sources anddestinations of the data are no longer observable while in

For the above reasons, in the core network will be used the~ ~ ~~ ~ ~ ~ ~ ~ ~ ~ Multiprotocol Label Switching (MPLS) in a few years andI Phvsical Fiber Plant I

Fig.2 P over DWDM protocol Stacks

m. LABELWITCHINGTECHNOLOGYOne reason that we eliminate the redundant layers and

employ a DWDM network is for the cost efficiency. Andanother is to boost speed up. One of the methods, increasingpacket transfer speed, is using tag scheme. Because the systemthat would transfer a received packet have to scan only the labelin a packet rather than look into the inside of packets. And thereare some other advantages of using labeling. A key feature oflabeling is its support for explicit routes. Explicitly routedLabel Switched Paths are farmore efficient than he sourceroute option in IP.

Many organizations use private networks built using leasedlines to connect multiple sites. A carrier offering that emulatesthe secure, reliable, and predictable behavior of these networksover shared carrier facilities holds the promise of providingextra service revenues to the carrier, while also lowering thecost of ownership bome by the customer. VPNs are anemulation of these Private Networks across carrier facilities insuch a manner that each customer perceives himself to berunning on a Private Network. The carrier's infrastructure hasbeen 'Virtualized' to support many independent mutuallyinvisible networks. Labeling is a key ingredientin buildingsuchnetworks. The label switching forwarding component is notspecific to a particular Network Layer. Label switching is alsoable to operate over virtually any Data Link Layer protocols.

Label switchingalso has the advantage of a clean separationbetween its control and forwarding functions. Each part canevolve without impacting the other part, which makes theevolution of networks easier, less costly, and less prone toerrors.

One other advantage of label switching that is not generallyvisible to the user is that it supports all types of forwarding:unicast, unicastwith ype of service, and multicast packets.

access network also need to expend capacity by employing labelswitching so that the label exchange will be occurred in theborder between an access node and a backbone edge router.Toimplementthis configuration, the label format and control plainin an access network had better take after those in a corenetwork.

Previous Fig.3 shows the extended PPP structure thatincludes MPLS shim header in a PPP frame.

IV. ACCESSETWORKR C ~ C T U R E SA . In a I O Gigabit EthernetIf a 10Gigabit Ethernet is used in access network, it is veryeasy to migrate an extended labeled PPP. Because the 10

Gigabit Ethernet fixme (802.3ae) follows a standard Ethernetflame (802.3). And the performance of 10Gigabit Ethemet thatis relatively not expensive is high. It was already well studied tosend PPP frames over Ethemet [ 5 ] .Therefore we can insert theextended labeled PPP frame over 10 Gigabit Ethemet Thefixme structure is shownFig. 4.

.OY"II Y / From 1OGEAF i g 4 Extended labeledPPP Structure over 10GigabitEthemetp w

B. In a Resilient Packet Ring ArchitectureAnother choice is that we employ the new topology that is

using packet ring architecture. Actually most of the realFig.3 Extended labeled PP P Structure infrastructure is constructed as a ring topology. Basically thisResilient Packet Ring scheme is based on the Ethernet Rmg.Reuse Protocol. As you can see from the name, this protocolReuse protocol useS both two rings for active packet transfer,

switching upon the various that The h h e n t a l protocol ofthe Resilient packet Ring is Spatialhave been tried for IP with ATM-basedsub-~e"ks Thisprocedures and protocols that deal with issues such as addressresolution and the different models for multicast and resource

re"% the med for complex consists of*o rings* The feature is that the spatial

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IP

PPPPHY

which is distinguished from other ring type architectures.Because most of other ringarchitectures use one activeringandone backup ring. So this Spatial Reuse Protocol is two timesefficient if the protection and restoration is guaranteed.Intelligent Protection Switching (IPS) [6] solves the protectionand restoration problem.SRP derives its name from the protocol's

destination-strippingoperation. Previousdata ring technologiessuch as FDDI or Token Ring did source stripping. Thus,because each ring node can source packets onto the ringconcurrently, this provides a major opportunity to maximizering bandwidth.

To adapt the extended labeled PPP, Spatial Reuse Protocol'sstack is modified like Fig. 5.

4 IP- Label. PPP-like e PPP-likeP H Y . P H Y 4 D P H Y

IP payloadFig. 5 Extended labeled PPP Structureover Resilie nt Packet Ring

The first row of Fig. 5is a Spatial Reuse Protocol version2.0Generic header format. And the second row is MPLS shimheader format. The last row is the payloadof he data packet in aPPP frame.

C. In a Passive Optical Network ArchitectureBut the network consists of asymmetrical subscribers or the

traffic of the subscribers is concentrated on one node in thenetwork, such a ringnetwork is not efficient. In th i s case we hadbetter use star of tree topology. The Passive Optical Network(PON) has tree topology.

The typical specifications for the broadband PONS currentlybeing deployed are splitting factors below 32, a range of up to20 km,and trammission speedup to 622 h4b/s.However, for thelong-term evolution of the core network, an extensive nodeconsolidation is expected since switching cost decreases withthe size of the switching site.As a consequence, the range of theaccess network will increase significantly. Ranges of up to 100km are being envisaged. In addition, since the cost of aswitching node is determined above all by the line cards, thenumber of accesses must be minimized. Hence, an accessnetwork is needed that multiplexes a large number ofsubscribers (around 2000) on a single line termination.

Recently there are a lot of study activities in the field of PON.Fig. 6 shows briefly a SuperPON system, which extendsdistance up to 100 km and increase the capacity toaccommodate subscribers.

Core Access networkn

- * c0 -90 km 0 - lO km

SuperP:JH 1:B482488 I 31 1 MMJsFig.5 Extended labeled PPP Structure overResilie nt Packet Ring

Fig. 7 Extended labeled PPP S t r u m ver PON systemV. CONCLUSION

This ring architecture is proper topology among fair loadsharing nodes, which have same upload bandwidth and download bandwidth. But in the case of raffic is concentrated on onenode, RPR is not efficient. So the optimized access networkwould be combined form. The traffic of individual subscribersis usually heading for the core network. Therefore the treearchitecture is preferred. And the other side, access corenetwork, statistically the aggregated traffic would be distributedto each nodes with equal amount.

Hence, the optimized topology is like Fig. 8.

Customel'saccess passiveoptical network

7 3 2 8

Fig. 8 Optical acce ss network3.r

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295ACKNOWLEDGMENT

This work was supported in part by the Electronics andTelecommunications Research Institute (ETRI), KoreaTelecom, and KOSEF. Andth is articleis the architecturepart ofthe whole access network study.

REFERENCES[l ] Chunming Qiao, Labeled Optical Bust Switching for IP over WDMIntegration, IEEE Communication Magazine September 2000.[2] Mooi C. Chuah et al., QoS Mapping Extensions to Multilink PPP,,une 1999.[3] Mike Davison et al., L2TP Over -5 and FU,

,pril 1999.[4] Yves TJoens Layer et al., Two Tunneling Protocol : ATM accessnetwork extensions, 4faft-ietf-pppext-l2tp-atmext-O1&e,une 1999.[5] L. Mamakos et al., A Method for Transmitting PPP over Ethernet(PPPoE), RFC2516, February 1999.[6] Sparial Reuse Protocol, white paper, Cisco Systems, 2000.[7] K. Slower et al., The PPPMultilink Protocol (MP), RFC 1990, August1996.[SI K. Nichols et al., Dekition of the differentiated Services Field @SField) in the P v4 and IPv6 Headers, RFC 2474, December 1998.[9] Reuven Cohen, Service provisioning in an ATM-over-ADSL Access

network, IEEE Communication Magazine, October 1999.[lo] Christoper Metz, A PointedLook at the Point to Point[1 11 haft-kompella-labeling-optical-00[12] G.L Papadimitriou * , AN. Miliou, AS. omportsis, an optically

controlled optical network,

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Point to Point Label Switching Protocol for Optical Access Networks

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