Study of LSP arrangement schemes in label switch networks

Copyright © 2005 John Wiley & Sons, Ltd.

INTERNATIONAL JOURNAL OF NETWORK MANAGEMENTInt. J. Network Mgmt 2005; 15: 421–431Published online in Wiley InterScience (www.interscience.wiley.com). DOI: 10.1002/nem.585

Study of LSP arrangement schemes in label switch networks

By Yen-Wen Chen*,†

Label switch paths (LSP) are regarded as the routing components of anend-to-end connection in label switching network from the trafficengineering point of view. Thus, an end-to-end connection may travelmore than one LSP. The QoS of this end-to-end connection relies on theperformance of each LSP it travels. Therefore, to carefully arrange LSP isan essential step towards QoS networks. Generally speaking, the capacityof a specific link is not allocated for high-priority LSP because it willcause inflexibility in the scheduling process. In this paper, the best-fitshortest path (BSP) assignment and the worst shortest path (WSP)assignment schemes are proposed for the arrangement of label switchpaths. In order to provide flexibility in packet scheduling, we propose thatthe BSP scheme to be applied for allocation of low-priority LSP and theWSP scheme is used for the arrangement of LSP with high priority. Basedon these two schemes, we extend them with elastic bandwidth allocationto prevent the bandwidth of the link from being occupied by the higherpriority LSP. The experimental results indicate that, compared to the BSP-only scheme, the proposed hybrid scheme demonstrates a more efficientway of arranging prioritized LSP. Moreover, the proposed elasticconstrained bandwidth allocation scheme also illustrates a rather goodperformance in smoothing the link utilization of high-priority LSP.Copyright © 2005 John Wiley & Sons, Ltd.

Dr. Yen-Wen Chen received his Ph.D degree in electronic engineering from National Taiwan University of Science and Technology (NTUST)in 1997. Currently he is an associate professor of Department of Communication Engineering, National Central University, Taiwan, ROC. Hisresearch interests include IP over SDH/DWDM, ATM/MPLS/GMPLS, mobile networks, and network management.

*Correspondence to: Yen-Wen Chen, Department of Communication Engineering, National Central University, Taiwan, ROC.†E-mail: [email protected]

Contract/grant sponsor: National Science Council; contract/grant number: NSC 93-2213-E-008-034

Contract/grant sponsor: Ministry of Transportation and Communication; contract/grant number: MOTC-SATO-93-14

Introduction

Various services and applications pro-vided on the Internet generate demandon network transmission performance.

The traditional router experiences a bottleneck inthe forwarding of packets because each packet hasto be processed by the CPU before forwarding.When quality of service (QoS) is considered, moreprocessing time is required to examine QoS-related information, such as source/destination

addresses, port numbers and protocol types of thearrival packets. Unlike the traditional router, themulti-protocol label switch (MPLS) technique inte-grates the label swapping framework and networklayer routing to speed up packet forwarding.1,2 InMPLS, each packet is attached with a label by theedge router when it enters the MPLS domain. Basi-cally, the label is of short fixed length and can beregarded as an abstract representation of a specificforward equivalent class (FEC) of packets to beforwarded. The labelled packets are delivered fol-

lowing the established label switch path (LSP). AnLSP can be regarded as a list of links which areassociated with label swapping. The concept oflabel swapping used in MPLS is similar to thetechnique adopted in asynchronous transfer mode(ATM). Thus, the label is equivalent to virtual pathidentification (VPI) and virtual channel identifica-tion (VCI) fields in the ATM cell header. Althoughan LSP may travel several nodes, packets can beforwarded at wire speed if no congestion occurs.The proper arrangement of bandwidth is an essen-tial step toward this objective. Thus bandwidthshould be effectively allocated to the LSPs accord-ing to their performance requirements, especiallywhen QoS is considered. Although load balance isa major consideration in resource allocation oftraffic engineering, it is only suitable for best-effortservice. The allocation scheme would be moresophisticated if differential services were providedin the networks.

The packet forwarding path is determined bythe establishment of LSP. If the link is congested,path performance will undoubtedly be affected.Thus, in order to maintain the expected QoS, thelink capacity should not be over-allocated (espe-cially for the path with the higher priority). Severalrecent research studies have proposed methods todeal with the allocation of routing paths.3–7 Aminimum interference routing was proposed byKodialam and Lakshman3 to avoid the over-utilization of critical links. A load-balancing algo-rithm was proposed by Long et al.4 to consider utilization among links. The main subject of theabove articles focuses on the balancing of linkload. The wide deployment of Internet services toprovide different QoS for different applicationneeds is an essential trend of the development ofthe Internet. Integrated services8 and differentialservices9 are the main technologies proposed forthe provisioning of QoS on the Internet. An RSVP-based resource allocation scheme for different priority traffic in a wireless network environmenthas been proposed.6,7 From a scheduling point ofview, in addition to balancing the link load, high-priority paths (traffic) are not suitable in contend-ing with limited bandwidth within a link. Therewill be no flexibility for the scheduler to arrangemore bandwidth for instant bursts in traffic inhigh-priority paths if practically the whole band-width of the link is allocated to high-priority pathsin advance. In this paper, we study the assignment

methods of high-priority and low-priority LSPsover MPLS networks by considering fair utiliza-tion of network links. Our purpose is not only tosmooth the link utilization, but also to prevent thelink from being blocked by high-priority traffic.Both best-fit shortest path (BSP) and worst short-est path (WSP) schemes are proposed to illustratethe phenomenon of the assignment. A hybridmethod is then proposed for the arrangement ofprioritized LSP. Furthermore, an elastic con-strained bandwidth allocation scheme is proposedto prevent the link bandwidth from being occu-pied by the high-priority LSP.

Our purpose is not only to smooth thelink utilization, but also to prevent the

link from being blocked by high-prioritytraffic.

This paper is organized as follows. the basicoperation of MPLS is briefly overviewed in the fol-lowing section. In the third section, BSP and WSPassignment schemes are described; then, based onthe BSP and WSP, the hybrid BSP/WSP schemeand the elastic constrained bandwidth allocationscheme are proposed. Experimental examples areprovided in the fourth section to illustrate the per-formance of the proposed schemes. Conclusionsand discussion are provided in final last section.

Overview of Label SwitchNetworks

It is known that the traditional router will onlyperform routing and packet forwarding mecha-nisms on arrival of data packets. These two mech-anisms are clearly separated in the MPLS network.In MPLS, the label switch performs route selectionand configures the forward paths in advance sothat each packet can be forwarded at ‘wire’ speedwithout processing delay. The key issue of thisapproach is to manage the binding of the relativelabels within a path by using the label distributionprotocol (LDP).10,11 Each label switch router (LSR)maintains its label forwarding table according tothe information advertised through LDP. Datapackets can then be forwarded through consecu-

422 YEN-WEN CHEN

Copyright © 2005 John Wiley & Sons, Ltd. Int. J. Network Mgmt 2005; 15: 421–431

tive swapping of labels as shown in Figure 1. Thus,the processing delay can be greatly minimized ifthe labels of an LSP can be properly assigned inthe label forwarding table of each LSR.

In MPLS, traditional routing protocols are stillnecessary to determine the next hop of FECs. LDPis adopted to map labels into FECs. Thus, LSRexchanges the routing information through theexisting routing protocols to decide the routingpaths and then applies the LDP to create the LSPwith respect to the selected routing paths. Theinterconnection between the routing protocol andthe label distribution protocol is depicted in Figure2. As shown in Figure 2, the routing protocols areused to determine the next hop of each FEC, andeach FEC is bound by a specific label locally. Thebinding information (including the mapping ofFEC and the label) is then distributed to othernetwork nodes. Each entry in the label forwardingtable (used for label swapping) is created accord-ing to the local label assigned for a specific FEC,the next hop of FEC, and the information obtainedfrom remote binding.

In order to provide QoS over MPLS, the Inter-net Engineering Task Force (IETF) has proposedthe concept of a traffic trunk for traffic engineer-ing.12,13 A traffic trunk is basically a routing object

of QoS paths. A traffic trunk may consist of one ormore LSPs for the consideration of load balancing,reliability or QoS. Accordingly, a connection maytravel more than one traffic trunk if the QoS bud-geting of the traffic trunks can be well allocated.Using traffic trunks, the layering approach canhave the advantage of flexible management ofnetwork resources. Therefore, if the traffic trunk isapplied, the arrangement of LSPs may be morestatic and may be less correlated to the QoS of aspecific connection because, as described above, atraffic trunk is only one of the general routing com-ponents of the end-to-end connection. However,the requirements of the QoS performance parame-ters should be more rigorous because end-to-endQoS is not possible if the performance of individ-ual QoS components cannot be guaranteed. Typi-cally, this layering approach can be regarded as akind of differential service (end-to-end) over anintegrated service (each QoS component).

Using traffic trunks, the layeringapproach can have the advantage of

flexible management of network resources.

STUDY OF LSP ARRANGEMENT SCHEMES 423


Unlabeled Packet

Labeled Packet

5

MPLS Domain

7

13

8

25

IP Add. Label115.140.x.x 5

To 115.140.x.x

IP Add. Label

150.114.x.x 25

To 150.114.x.x

In label Out label

25 13

In label Out label13 85 7

In label Out IP Addr.

8 150.114.x.x

Label Switch Path

Figure 1. Operation concept of MPLS

LSP Arrangement Using BSP and WSP

In this paper, two basic schemes, BSP and WSP,are proposed for the arrangement of LSP in MPLSnetworks. The BSP scheme is based on the conceptof arranging the LSP in a ‘defragmented’ manner.Thus, the bandwidth allocated for an LSP isselected from the links such that it is just sufficientto meet the bandwidth requirement of the LSP. Theadvantage of the BSP scheme is that the LSPs tendto share the same links with other LSPs. Links withlarger bandwidth can be reserved for the needs ofLSPs requiring large bandwidth (thus reducing theproblem of bandwidth fragmentation). A request-ing LSP can be denoted as (s, d, b), where s and drepresent the source node and the destinationnode respectively, and b is the required bandwidthof the LSP. For a network topology G(N, L, C),where N is the set of nodes, L is the set of links,and C is the set of capacity of each link, the pro-cedure for the arrangement of an LSP by using BSPcan be stated as follows:

• Step 1: subtract b from the bandwidth of alllinks b to obtain a reduced graph G¢(N¢, L¢, C¢).

• Step 2: find the LSP with respect to the sourcenode (s) and destination node (d) by usingany shortest path-finding algorithm (e.g.Dijkstra’s algorithm);

• Step 3: add the links that are not selected bythe LSP to the bandwidth b.

The algorithm of the BSP scheme is illustrated inFigure 3.

On the other hand, the WSP scheme is designedin a ‘fragmental’ manner. Thus, the bandwidthallocated for an LSP is selected from the linkswhose residual bandwidths are larger. Thus, theWSP scheme tends to balance the traffic loadamong links. However, a path may travel throughseveral other links with a larger residual band-width before reaching its destination if there is noother constraint in selecting the paths. In order toprevent the occurrence of such a situation, we con-strain the LSP to be chosen with the minimumnumber of hubs manner. Thus, the paths areselected by considering the minimum number ofhubs first, and then choosing the path having thelargest residual bandwidth among them. Theadvantage of the WSP scheme is that the traffic can be spread over the network and the load can be better balanced. The procedure of arrange-ment of an LSP by using WSP may be stated asfollows:

• Step 1: subtract b from the bandwidth of alllinks to obtain a reduced graph G¢(N¢, L¢, C¢).

• Step 2: determine all the paths with minimumhub from source node (s) to the destination

424 YEN-WEN CHEN


Label ForwardingTable

RoutingInformation

Label BindingInformation

Routing protocols Label Distribution Protocol

LocalFree Label

Pool

FEC/Next hop

Label

LocalBinding

LabelDistribution

RemoteBinding

Figure 2. Routing protocols and label distribution protocols

node (d) by assuming the cost of each linkequals 1.

• Step 3: select the desired LSP with themaximum residual bandwidth, which can becalculated by the summation of the band-widths of the links that this path will travel,from the paths found in Step 2.

• Step 4: add the links that are not selected bythe LSP to the bandwidth b.

The algorithm of the WSP scheme is illustrated inFigure 4.

According to the above descriptions, bothschemes have their strengths. The BSP scheme hasthe advantage of efficiency of resource utilization,while the WSP scheme can effectively distributetraffic load. Actually, both schemes are helpful andcan compensate each other in the arrangement ofLSP in QoS networks. For traffic engineering inMPLS, each LSP is considered as a routable objectof an end-to-end connection. Therefore, each LSP should be carefully arranged to satisfy thedesigned QoS budget. Basically, a priority sched-uler can effectively allocate the bandwidth of a link

to the traffic streams with a different prioritythrough the statistical gain of multiplexing thosetraffic streams. If a link is full of traffic streamswith highest priority, the traffic scheduler willsuffer from flexibility in bandwidth allocation.Therefore, we propose the allocation of LSPs withdifferent priorities adopting different approaches.The arrangement of a high-priority LSP is betterapplied to the WSP so that the high-priority trafficcan be spread over different links, while the BSP scheme is used for the arrangement of low-priority LSP to gain the advantage of efficientresource utilization. Thus, a hybrid BSP/WSPscheme is proposed for the arrangement of prior-itized LSP.

In addition, based on the hybrid BSP/WSPscheme, an elastic factor is proposed to allocate thebandwidth in a more efficient way. The bandwidthis allocated in a conservative manner for theassignment of the high-priority LSP, and in anaggressive manner for the low-priority LSP. Let Ef,0 £ Ef < 1, be the elastic factor; the capacity of thelink is confined as (1 - Ef)C when arranging thehigh-priority LSP, and the capacity of the link isinflated as (1 + Ef)C when arranging the low-pri-ority LSP. Hence, for each link, the percentage ofbandwidth allocated to the traffic with high prior-ity will never exceed (1 - Ef) of the link capacity.The performance of the high-priority connectioncan be calculated as the link with load (1 - Ef)without considering the effect of the low-prioritytraffic if the high-priority traffic always has higherpriority of scheduling. Thus, the elastic factor canbe used as the parameter for the performancecontrol of LSP. This concept is similar to that of the control load service defined in the differentialservices.9

Experimental ResultsIn order to examine the arrangement perfor-

mance of the proposed scheme for prioritizedLSPs, two network topologies (case 1 and case 2)used elsewhere,3,14 shown in Figures 5 and 6, areapplied as experimental examples. The experi-mental topology of case 13 has 15 nodes and 28links and case 214 has 24 nodes and 43 links. Thelink capacity with dark links in case 1 is assumedto be 45 units and the light line is assumed to be12 units, while each link capacity of case 2 is



algorithm _ ( , , , )Best Fit s G D b

/*Initialize*/ for each node u NŒ

:uD = • ; *uv uvd d b= - ;

end for : { }S s= ; : 0sD = ;

while S is not empty u SŒ ;

for each v N SŒ - doif each vD > *

u uvD d+ ;

then vD := *u uvD d+

end ifend for

end while end algorithm

Figure 3. BSP algorithm

426 YEN-WEN CHEN


algorithm Worst_shortest(s,G,D,b,hop)/*Initialize*/

for each node u Œ N0 :uD = • ;

#uv uvd d b= - ;

end for : { }S s= ; : 0hop

sD = ; while S is not empty

u SŒ ; for hop :=1 to N-1

for each v N SŒ - do 1 #= max{ }hop hop

v u uvD D d- + except •end for

end forfind hop

vD which the minimum value of hop end while

end algorithm

Figure 4. WSP algorithm

1

5

12

13

14

15

98

4

2

1163

7 10

G=(15, 28)

Figure 5. Network topology of case 1

assumed to be 15 units. During the simulation,each node has an equal probability of beingselected as source or destination of a LSP. Two dif-ferent kinds of priorities are assumed. Each LSP isgenerated as LSP(si, di, bi, ti) in our simulation,where si and di denote the source node and desti-nation node, respectively, bi is the desired band-width and ti is the type, which can be either highpriority or low priority, of the LSP.

In our simulation, a number of LSPs, where thenumbers of high-priority and low-priority pathsare evenly distributed, are randomly generated torequest for establishment. In the proposed scheme,the establishment of high-priority LSP applies theWSP algorithm and the BSP algorithm is used forthe establishment of low-priority LSP. The BSP-only scheme, in which the BSP scheme is adoptedfor both the high-priority and low-priority LSP, isalso simulated for comparison. The average linkutilization Lutility is defined as

where N is the number of LSPs accepted, and bi

and Ci represent the bandwidth allocated and theoriginal bandwidth, respectively, of the ith linktravelled by an LSP. Thus, the average utilizationof links is calculated according to the average frac-tion of bandwidth used on links by the acceptedLSP.

Tables 1 and 2 show the simulated results of thenumbers of connections accepted and the average

LN

bCut ility

i

iiN

= ÂÂ1 link utilizations for both cases, respectively. It isnoted that the proposed scheme demonstrates ahigher acceptance ratio than the BSP-only schemein both cases. It is also noted that the averageacceptance ratio of case 2 is higher than that of case1 owing to the larger network bandwidth of case2 (15 * 43 = 645 units) compared to that of case 1(45 * 6 + 12 * 22 = 534 units). However, the differ-ence is not significant when the number of LSPsbecomes large (e.g. more than 100). The mainreason is that there are six links with large band-width (45 units) in case 1 whereas links in case 2



1

14

13

12

11

10

9

8

7

4

5

3

2 15 20

19

2418

6

2116

17

22

23

G(24, 43)

Figure 6. Network topology of case 2

No. of Acceptance ratio by the proposed Acceptance ratio by BSP-only schemeLSPs scheme

High priority Low priority High priority Low priority

Case 1 Case 2 Case 1 Case 2 Case 1 Case 2 Case 1 Case 2

25 13 13 12 12 13 13 12 12(100%) (100%) (100%) (100%) (100%) (100%) (100%) (100%)

50 23 25 24 25 19 24 18 23(92%) (100%) (96%) (100%) (76%) (96%) (72%) (92%)

75 30 34 30 33 23 26 24 27(78.9%) (92%) (78.9%) (87%) (63.1%) (70%) (63.2%) (71%)

100 35 35 33 36 25 28 24 27(70%) (70%) (66%) (72%) (50%) (56%) (48%) (54%)

125 35 36 36 37 25 26 27 27(55.6%) (57.1%) (58%) (59.6%) (39.7%) (41.9) (42.8%) (42.8%)

150 36 37 38 38 26 27 29 27(48%) (49.3%) (50.7%) (50.7%) (34.7%) (36%) (38.7%) (36%)

Table 1. Performance of LSP acceptance ratio

have equal bandwidth (15 units). It will causemore fragmented (residual) bandwidth on links incase 2 and, therefore, more bandwidth is wasted.It is also noted that the difference in average linkutilization for both schemes does not seem to besignificant. The reason is that the calculation of theaverage link utilization is based on the pathsaccepted. Thus, the proposed scheme can spreadthe high-priority LSP over the network by usingthe WSP scheme to achieve a higher acceptanceratio.

It is noted that the proposed schemedemonstrates a higher acceptance ratio

than the BSP-only scheme in both cases.

In order to realize the utilization on each link,we examine the utilization of individual links ofcase 1 as shown in Figures 7 and 8 (100LSPs are

428 YEN-WEN CHEN


No. of Average link utilization by the Average link utilization by BSP-LSPs proposed scheme only scheme



25 0.186 0.182 0.172 0.169 0.206 0.191 0.192 0.18850 0.316 0.305 0.259 0.246 0.343 0.322 0.232 0.22975 0.397 0.401 0.331 0.342 0.401 0.405 0.263 0.27100 0.44 0.422 0.343 0.35 0.443 0.409 0.287 0.283125 0.44 0.424 0.359 0.351 0.463 0.411 0.291 0.283150 0.443 0.425 0.382 0.353 0.462 0.412 0.291 0.283

Table 2. Performance of average link utilizations

Link

1

1.2

1

0.8

0.6

0.4

Util

izat

ion

0.2

02 3 4 5 6 7 8 9 10111213141516171819202122232425262728

LowHigh

Figure 7. Link utilization of the proposed scheme

generated). Both utilizations of high-prioritytraffic and low-priority traffic are depicted. Thisindicates that the proposed scheme shows a betterutilization of the links (e.g. links 8, 9, 14, 15). Forthe BSP-only scheme, although the bandwidth uti-lizations of some links are zero (links 9 and 17); itis not easy to accept other LSPs because the band-widths of some links are exhausted.

For the elastic approach, we examine the accep-tance ratio of LSPs and the average link utilizationin both cases as shown in Table 3. The elastic factorEf is assumed to be 0.25 in this simulation. Thisindicates that the acceptance ratio of the high-priority LSP is smaller than without the elasticapproach in Table 1. However, the acceptance ratioof the low-priority LSP has increased when com-



Link

1

1.2

1

0.8

0.6

0.4

Util

izat

ion

0.2

02 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28

LowHigh

Figure 8. Link utilization of the BSP-only scheme

No. Acceptance ratio by the proposed Average link utilization by theof scheme with elastic approach proposed scheme using elasticLSPs approach



25 13 13 12 12 0.184 0.179 0.165 0.156(100%) (100%) (100%) (100%)

50 22 24 25 25 0.302 0.298 0.296 0.287(88%) (96%) (100%) (100%)

75 24 25 36 38 0.332 0.324 0.416 0.404(64.9%) (67.6%) (97.3%) (100%)

100 27 26 40 43 0.338 0.325 0.442 0.451(54%) (52%) (80%) (86%)

125 27 26 45 44 0.338 0.325 0.474 0.458(42.8%) (41.3%) (71.4%) (69.8%)

150 27 26 47 47 0.338 0.325 0.496 0.466(36%) (34.7%) (62.7%) (62.7%)

Table 3. Performance of acceptance ratio and average link utilizations using elastic approach

pared to the scheme without elastic concept. Thereason is that the applicable bandwidth of eachlink is confined and inflated by the elastic factor inarranging the high-priority and low-priority LSP,respectively. Thus, the bandwidth that can be allo-cated for high-priority traffic is 25% less than thatwithout the elastic approach. Although the accep-tance ratio of the high-priority LSP has decreased,the utilization of each link is bounded by 75% ofthe total capacity. The performance of the high-pri-ority path can be regarded as the control load QoSunder a 0.75 load. In Figure 9 the bandwidth usageof each link for high-priority traffic in case 1 is con-fined by 75%. It is also noted that the actual band-width allocated for each link may exceed itslimitation (100%) because of bandwidth inflationfor low-priority LSP. This will not be a problembecause the exceeded part is allocated for low-pri-ority traffic and will not affect the performance ofhigh-priority LSP.

ConclusionsLSPs are regarded as individual QoS routing

components of a connection for traffic engineeringof MPLS. End-to-end QoS is determined by the

QoS components selected. It is an important issueto study the allocation of the routing objects (LSPs)with various kinds of QoS to achieve this goal. Inthis paper, a hybrid WSP/BSP scheme is proposedfor the arrangement of LSP over MPLS networks.Two main objectives are considered in the pro-posed scheme. The first one is to disperse link uti-lization of the high-priority path so that thescheduler can be more flexible in forwardingpackets. The QoS of an LSP can then be guaran-teed accordingly. The other objective is to effi-ciently allocate the network resource for theaccommodation of more LSPs with low priority. Inorder to accommodate more traffic and to confinethe load of traffic with high priority, an elasticfactor is also proposed for compensation of thehybrid WSP/BSP scheme. The elastic approachcan guarantee the performance of high-priorityLSP just like a path with predetermined trafficload. The efficiency of the proposed scheme isexamined through the simulation of two networktopologies. The experimental results of both casesindicate that the proposed schemes can effectivelyachieve the above objectives. Future researchissues include the design of various classes of LSPwith respect to different elastic factors, and thearrangement of QoS budget by using a set of QoS

430 YEN-WEN CHEN


Link

10

0.2

0.4

0.6

0.8

1

1.2

1.4

Util

izat

ion

3 5 7 9 11 13 15 17 19 21 23 25 27

LowHigh

Figure 9. Link utilization of the proposed scheme with elastic approach

components (LSPs) for the achievement of end-to-end QoS.

AcknowledgementsThis research was supported in part by the

grants from National Science Council (NSC93-2213-E-008-034) and Ministry of Transportationand Communications (MOTC-SATO-93-14).

References1. Rosen E. Multiprotocol label switching architecture.

IETF rfc-3031, 2001.2. Xiao X, Li LM. Internet QoS: the big picture. IEEE

Network 1999; March/April: 8–18.3. Kodialam M, Lakshman TV. Minimum interference

routing with applications to MPLS traffic engineer-ing. In Proceedings of IEEE Conference on ComputerCommunications (IEEE Infocom 2000), New York,March 2000; 2566–2579.

4. Long K, Zhang Z, Cheng S. Load balancing algo-rithms in MPLS traffic engineering. In IEEE Work-shop on High Performance Switching and Routing, 2001,Beijing University of Posts and Telecommunica-tions, China; 175–179.

5. Floyd S. Link-sharing and resource managementmodels for packet networks. IEEE/ACM Transactionson Networking 3(4): 356–386.

6. Yoram B. The complementary roles of RSVP and dif-ferentiated services in the full-service QoS network.IEEE Communication Magazine 2000; February:154–162.

7. Moon B, Aghvami H. RSVP extensions for real-timeservice in wireless mobile networks. IEEE Commu-nication Magazine 2001; 12(December): 52–59.

8. Shenker S, Partridge C, Guerin R. Specification ofguaranteed quality of services. IETF rfc 2212, Sep-tember 1997.

9. Wroclawski J. Specification of the controlled loadnetwork element services. IETF rfc 2211, September1997.

10. Xiao X, Hannan A, Bailey B, Li LM. Traffic engi-neering with MPLS in the Internet. IEEE NetworkMagazine 2000; March/April: 28–33.

11. Andersson L, Doolan P, Feldman N, Fredette A,Thomas B. LDP specification. IETF rfc-3036, 2001.

12. Awduche D, Malcolm J, Agogbua J, O’Dell M, MacManus J. Requirements for traffic engineeringover MPLS. IETF rfc 2702, 1999.

13. Kompella K, Rekhter Y, Berger L. Link bundling inMPLS traffic engineering. IETF draft-ietf-mpls-bundle-04.txt, 2003.

14. Zhu K, Zang H, Mukherjee B. A comprehensivestudy on next generation optical grooming switches.IEEE Journal on Selected Areas in Communications2003; 21(7): 1173–1186.



If you wish to order reprints of this or anyother articles in the International Journal of Network Management, please [email protected].

Documents

Study of LSP arrangement schemes in label switch networks