Table Of Contentiiv
PREFACE
"Teletraffic Engineering in the Internet Era"
The Internet Era has already begun. Are we eye-witnessing the beginning of a networking Era
with no frontiers? Are we eye-witnessing the dawn of a new communications era in which the
way we communicate will radically change? Are we moving away from the traditional E&M
(Ear & Mouth) signaling to a more powerful way of communicating?
The Internet has no owner. The IP suite protocol is a ed facto open standard that anyone can
use, modify its code, perform experiments, and develop new services upon it. In despite of its
lack of Quality of Service support, IP has been used for the deployment of new multimedia
services over the net, challenging the traditional way we do business in telecommunications.
However, providing the Quality of Service required by multimedia services demands new
network design approaches. Multi-service network entails additional challenges to teletraffic
engineers, such as modeling burst traffic, bandwidth allocation for real time and mass data
applications, resource reservation, routing algorithms, mobility management, provision of
Quality of Service guarantees, pricing and economic investments.
ITC-17 addresses issues of paramount importance, such as the development of models and
strategies to cope with the exploding increase of traffic, the need of high bandwidth in access
networks, the interworking of fixed and mobile networks and the reliability for the
forthcoming myriad of services. The conference theme, "Teletraffic Engineering in the
Internet Era", underlines the evolutionary progress needed in the area of Teletraffic Theory
and Engineering for converging networks and services.
Selected papers were refereed by International experts, and, in addition, were reviewed and
ranked by a small group of experts during the Technical Committee meeting held in
Campinas, Brazil. Such procedure followed the successful approach used by previous ITCs.
ITC 71 received 381 submissions, and 97 papers were selected; 21 for plenary presentation
and 58 for parallel sessions organized around the following themes: Admission Control -
RSVP, Resource Allocation, Resource Allocation in Wireless Network, Multimedia
Provisioning, Traffic Characterization, Performance Analysis of Wireless Systems, Traffic
Engineering, Network Planning, TCP Performance, Network of Queues, Scheduling &
Administration Control, TCP Modeling, IP QoS Diff Service, Queuing Theory, IP
Performance Measurement, Network Flow Analysis, Pricing of Telecom Services. The broad
topic of" Internet QoS" received major attention from the Teletraffic community. RSVP, Diff
service, TCP performance, IP traffic characterization and measurements, and Multimedia
Provisioning are the main areas covered in this edition.
We hope to have minimized unfairness. Our heartfelt thanks to all members of the National
and of the International Technical Program Committees, as well as external reviewers for
their support and cooperation during the review process. It was a pleasure to work with them.
iiiv
We are in debt with many people who helped us throughout the organization process. Our
gratitude goes to:
The Institute of Computing at the State University of Campinas (UNICAMP) for the
computing and administrative support,
Antonio P. Castro Jr, Nelson G. M. Leme, Michele M.A E. Lima, Cesar A V. Neto and
Sergio A Yunes for the administrative support,
David Nicol, designer of WIMPE, the software used for managing the electronic paper
submission, for his help during some difficult times.
We would also like to extend our special thanks to:
Juarez Martinho Quadros do Nascimento, Executive Secretary to the Ministry of
-
Communications; to Renato Guerreiro, President of the National Telecommunications
Agency (ANATEL).
The Ministry of Communications, to the National Telecommunications Agency -
-
ANATEL, to the State University of Campinas - UNICAMP, and to the Center for
Research and Development - CPqD, our institutional sponsors,
- The International Telecommunication Union for sponsoring the Joint ITC/ITU Workshop,
- GVT, NORTEL and InnoWave for sponsoring the publication of this book.
We are thankful to Paul Kuhn for his efforts and for sharing with us his valuable experience.
We would like to express our sincere gratitude to Carlos Alberto Costa Nunes and Marcos
Bafutto, Chairman and Vice-Chairman of the Executive Committee, respectively, for their
effort in making ITC 71 happen.
Finally, we thank all authors who undoubtedly contributed to the high technical quality of ITC
71
Jorge Moreira de Souza
Nelson L.S. da Fonseca
Edmundo A. de Souza e Silva
Executive Committee
Carlos Alberto CostaN unes Chairman
Marcos Bafutto Vice-Chairman
Jos6 Roberto Boisson da Marca Vice-Chairman
Jorge Moreira de Souza TPC Chairman
Nelson Luis Soares da Fonseca TPC Vice-Chairman
Edmundo Albuquerque de Souza e Silva TPC Vice-Chairman
Jos6 Augusto Suruagy. Monteiro Local Arrangements
Vfinea Rabelo Executive Secretary
National Committee
Carlos Alberto Costa Nunes, GVT Jo~o Mello da Silva, Brasil Telecom
Marcos Bafutto, ANATEL Ivan Campagnolli Junior, Embratel
Jos6 Roberto Boisson da Marca, PUC-Rio Ayrton Capella Filho, Brasil Telecom
Jorge Moreira de Souza, Lucent Nelson Lopes Pimentel, Telefonica
Nelson Luis .S da Fonseca, IC-UNICAMP Eduardo de Oliveira Ramalho, Embratel
Edmundo A. de Souza e Silva, UFRJ Bruno Viana, Telemar
Jos6 Augusto Suruagy Monteiro, UNIFACS Guilherme Nunes, Consulting
Vfinea Rabelo, Ministry of Communications Ricardo Augusto V. do Nascimento, OsX
Luciene Tavares, Intercfimbio S6rgio Carlos Costa, INTEGRA
International Advisory Council- IAC
Paul .J Kuehn, Germany (Chairman)
Villy Baek Iversen, Denmark (Vice Chairman)
Patricia Wirth, United States (Secretary)
.A Jensen, Denmark (Chairman Emeritus)
National Representatives
David Everitt, Australia Vladimir .I Neiman, Russia
Carlos .A Costa Nunes, Brazil Oscar Gonzalez-Soto, Spain
Jim Yan, Canada Ulf Korner, Sweden
Prosper Chemouil, France Peter Key, United Kingdom
Mario Bonatti, Italy Bharat Doshi, United States
Konosuke Kawashima, Japan Manuel Villbn-Altamirano, UIT-T
Onno Boxma, Netherlands Lars Engvall, UIT-D
National Technical Program Committee
Virgilio Almeida UFMG Cristina .D Murta UFPR
Marcos Bafutto ANATEL Eunice .L Pissolato CPqD
Rosangela Coelho IME Jos6 .F de Rezende UFRJ
Jean M. Farines UFSC Paulo .A Rodrigues UFRJ
Nelson .L .S Fonseca Unicamp Djamel Sadok UFPE
Anilton .S Garcia UFES Luiz .F Gomes Soares PUC Rio
Antonio .C Lavelha CPqD Edmundo A.de Souza e Silva UFRJ
Rosa M. Le~o UFRJ Jos6 .A Suruagy Monteiro UNIFACS
Antonio .A .F Loureiro UFMG Edson Ursini CPqD
Jorge Moreira de Souza Lucent Michel D.Yacoub Unicamp
International Technical Programme Committee
Ake Arvidsson Sweden Tony Krzesinski outh Africa
Chris Blondia Belgium Paul J.Kuehn Germany
Onno Boxma Netherlands Ralf Lehnert Germany
H6ctor Cancela Uruguay Yonatan Levy USA
Olga Casals Spain Michel Mandj es Netherlands
Joachim Charzinski Germany Raymond Marie France
Prosper Chemouil France Marco A.Marsan Italy
Ed Coffman USA Debasis Mitra USA
Mike Devetsikiotis Canada Arne A.Nilsson Denmark
Peder Emstad Norway Ilkka Norros Finland
Lars Engvall ITU Baron Peterssen South Africa
David Everitt Australia Guido Petit Belgium
Serge Fdida France Michal Pioro Poland
Georges Fiche France Federico K.Rodriguez Mexico
Wolfgang Fischer Germany Gerardo Rubino France
Andrea Fumagali USA Mike Rumsewicz Australia
Richard Gail USA Hiroshi Saito Japan
Giorgio Galassi Italy Yutaka Takahashi Japan
Annie Gravey France Phuoc Tran-Gia Germany
Davide Grillo Italy Hans Van Den Berg Netherlands
Richard Harris Australia Manuel Villen-Altamirano Spain
Villy .B Iversen Denmark Jorma Virtamo Finland
Peter Key United Kingdom Robert E.Warfield Australia
Ulrich Killat Germany Bruce Whitaker USA
Daniel Kofman France Pat Wirth USA
UlfKomer Sweden Moshe Zukerman Australia
Marwan Krunz USA
ix
List of Reviewers
Aalto, .S Emstad, .P Koike, A.
Adan, I.J.B.F. Engvall, .L Komer, U.
Agrawal, .A Enriquez, .J Krunz, M.
Akin, .O Everitt, .D Krzesinski, T
Almeida . V Farel, .R Kuehn, P.J.
Andr6s-Colfis, .J Farines, J.M. Kumaran, K.
Anelli .P Fdida, .S Kwanishi, K.
Aracil, .J Ferreira de Rezende .J Laevens, K
Arvidsson, A. Fiche, .G Lai, W.S.
Azevedo Gomes, A.T. Fischer, W. Lavelha A.C.
Bafutto M. Fonseca N.L.S. Lego, R.M.
Baumann, M Fumagalli, A. Lehnert, R.
Berg, H. van den Furman, .D Levy, Y.
Blondia, .C Furuya, H. Lo Cigno, R.
Bosch, .S van den Gail, .R Lobo, .J F.
Boucherie, R. Galassi, .G Loureiro, A.A.F.
Boxma, .O Garcia A.S. Lutton, J-L
Brown .P Gavilanes, .C Magee, F
Buchli, M. Gomes Soares, L.F. Mandjes, M.
Busson, .A Gravey, .A Mannersalo, .P
Campanholi Tome, S.M. Grillo, D. Marie, R.
Cancela, H. Guillemin .F Marsan, M.A.
Cardieri, .P Harris, R. Mellia, M.
Casals, .O Heyman, D. Menth, M.
Casellas, R. Hoey, .G van Meo, M.
Casetti, .C Hogendorn, .C Misra, V.
Charzinski, J Houck, .D Mitra, D.
Chemouil, .P Houdt, .B van Moreira de Souza .J
Choe, .J Ivanovich, M.V. Muchaluat, D.
Choudhury, .G Iversen, V.B. Mueller, T
Cobb, .J Jue, .J Munafo, M
Coelho R. Kamiyama, N. Murta C.D.
Coffman, .E Karasaridis, .A Neame, .T
Colcher, .S Kaspher, A. Nilsson, A.A.
Cole, .R Katayama, .T Norros, .I
Collange .D Kawahara, .R Nunez Queija, R.
Costa Andrade, E.L. Kawanishi K. Nyberg, .C
Costa .L Key, .P Oelrich, M.
de Boer, P-T Killat, U. Ohara, H.
De Vleeschauwer, D. Kilpi, .J Olivier .P
Devetsikiotis, M. Klaoudatos, .G Ooms, D.
Dupuis A. Klincewicz, .J Owerzaski .P
Eckberg, .T Koehler, .S Padhye, .J
1E Khadiri, M. Koerner, .U Palmowski, Z.
Elizondo, A. .J Kofman, .D Papavassiliou, .S
iix
Peeters, .S S aniee, .I Uitert, M. van
Perez, .S Sasaki, T. Ursini, E.
Peterssen, B. Schlegel, .S Vicari, N.
Petit, G.H. Schueler, J Viera, O.
Pioro, M. Schweigel, M Villen-Altamirano, M.
Pissolato, E.L.M. Segal, M. Virtamo, J.
Poppe, F. Shulman, H. Wang, Q.
Rob Kooij, R. Soares L.F.G. Warfield, R.E.
Rodrigues, P.A. Souza e Silva E.A. Whitaker, B.
Rodriguez, F.K. Spaey, K. Wirth, P.
Rougier, J.L. Staehle, D. Yacoub, M.D.
Rouskas, G. Suruagy, J.A. Yokoi, H.
Rubino, G. Tacca, M. Zemor, G.
Rumsewicz, M. Takahashi, Y. Zhao, J.
Sadok D. Toyoizumi, H. Zheng, S.Q.
Sahu, .S Tran-Gia, P. Zukerman, M.
Saito, H. Tuffin, B.
Salamatian K. Tutschku, K.
ITC 17 / J. Moreira de Souza, N.L.S. da Fonseca and E.A. de Souza e Silva (Editors)
(cid:14)9 2001 Elsevier Science B.V. All rights reserved.
A New Threshold-Based Policy for Label Switched Path (LSP) Set-up in
MPLS Networks
C. Scoglio ,a T. Anjali ,a J. C. de Oliveira ,a I. F. Akyildiz ,a and G. Uhl b
aBroadband and Wireless Networking Lab,
School of Electrical and Computer Engineering,
Georgia Institute of Technology, Atlanta, GA 30332, USA
bRaytheon Information Technology and Scientific Services,
Lanham, MD 20706, USA
In this paper, a new policy is introduced to determine and adapt the MPLS network
topology based on the current traffic load. The objective of the new policy is to minimize
the costs involving bandwidth, switching and signaling. The new policy is based on a
threshold criterion and requires only the knowledge of some parameters locally stored in
the source router. The value of the threshold depends on the cost coefficients and on
the length (number of intermediate hops) of the LSP. The new policy also performs a
filtering control to avoid oscillations which occur due to highly variable traffic. The new
policy has been evaluated by simulation and numerical results show its effectiveness and
the according performance improvement.
1. Introduction
MultiProtocol Label Switching (MPLS) is a switching technology to forward packets
based on a short, fixed length identifier called label. Using indexing instead of long
address matching, MPLS achieves fast forwarding. Labels are used as indices of a table
that contains the connection path. An MPLS network consists of Label Switched Paths
(LSPs) and edge/core Label Switch Routers (LSRs). The LSRs store the label translation
tables. Core LSRs provide transit services in the middle of the network while edge LSRs
provide an interface with external networks. Packets with identical label are forwarded
on the same LSP. LSPs are virtual unidirectional paths established from the sender to
the receiver 1. An extension of the ReSource reserVation Protocol (RSVP) is used to
establish and maintain LSPs in the backbone 2. One of the most significant applications
of MPLS will be in Traffic Engineering (TE) 3,4, since LSPs can be considered as virtual
traffic trunks that carry flow aggregates generated by packet classification.
Packet classification is also performed in the Differentiated Services (DiffServ) model
which is based on classifying and aggregating individual microflows, at the edge of the
network, into one of several Behavioral Aggregates (BAs) 5. A Per-Hop Behavior (PHB)
defines the service a packet should receive in the network. Currently, packets are treated
at each router based on two standard PHBs :7,6
(cid:12)9 Expedited Forwarding (EF): minimizes delay and jitter. It provides the highest level
of aggregate QoS. Any traffic exceeding the traffic profile is discarded.
(cid:12)9 Assured Forwarding (AF): has four classes and three drop precedences within each
class. Traffic compliant with the pre-negotiated traffic profile is delivered with a
higher probability than the non-compliant traffic.
There are some open research problems related to DiffServ model:
(cid:12)9 How can the DittServ model be extended to heterogeneous networks?
(cid:12)9 How can the network resource utilization be improved by performing traffic engi-
neering at DiffServ class level?
For both cases, a solution can be provided by using MPLS, after defining a mapping
between DiffServ classes and LSPs. To the best of our knowledge, this mapping solution
is still an open research problem.
Following the IETF 8,9 suggestions, three class types can be defined with each being
carried on a virtual layered MPLS network by itself, e.g.,
(cid:12)9 MPLS net1 as Class type ,O i.e, Best Effort
(cid:12)9 MPLS net2 as Class type ,1 i.e., Expedited Forwarding (/or real time traJfic)
(cid:12)9 MPLS net3 as Class type 2, i.e., Assured Forwarding 1 and 2 (/or low loss classes)
Here, each physical link capacity is partitioned among different MPLS networks, and
a maximum capacity (fixed percentage of the total link capacity) is assigned to each
partition. The unused reserved bandwidth is then used for Best Effort (BE) traffic. The
design and management of the above MPLS networks are a fundamental key to the success
of the DiItServ-MPLS mapping. However, many problems such as the definition o the
network topology, LSP dimensioning, LSP set-up/tear-down procedures, LSP routing, and
LSP adaptation .for incoming resource requests, need to be solved. The classical network
design methods, which are performed off-line by using a-priori known traffic demand,
are not suitable for MPLS networks 01 due to the high unpredictability of the Internet
traffic.
A fully connected MPLS network, where every pair of LSRs is connected by a direct
LSP, is very inefficient 11 due to the high signaling cost and the management of a large
number of LSPs. The signaling cost is in the order of N ,2 where N is the total number
of routers. Two different approaches, traJfic-driven and topology-driven, can be used for
MPLS network design. In the tra~c-driven approach, the LSP is established on demand
according to a request for a flow, traffic trunk or bandwidth reservation. The LSP is
released when the request becomes inactive. In the topology-driven approach, the LSP
is established in advance according to the routing protocol information, e.g., when a
routing entry is generated by the routing protocol. The LSP is maintained as long as the
corresponding routing entry exists, and it is released when the routing entry is deleted.
The advantage of the traffic-driven approach is that only the required LSPs are set-up;
while in the topology-driven approach, the LSPs are established in advance even if no
data flow occurs.
A simple LSP set-up policy based on the traffic-driven approach has been proposed
in 11, in which an LSP is established whenever the number of bytes forwarded within
one minute exceeds a threshold. This policy reduces the number of LSPs in the network;
however, it has very high signaling costs and needs high control efforts for variable and
bursty traffic in the case of a fully connected network.
In this paper, we introduce a new decision policy that provides an on-line design for
MPLS network depending on current traffic load. The proposed policy is a traffic-driven
approach and balances the signaling and switching costs. By increasing the number
of LSPs in a network, the signaling costs increase while the switching costs decrease.
In our policy, LSPs are set-up or torn-down depending on the actual traffic demand.
Furthermore, since a given traffic load may change depending on time, the new policy
also performs filtering in order to avoid oscillations which may occur in case of variable
traffic.
This paper is organized as follows. In section 2, the LSP set-up problem is formulated
and solved, and the policy structure is described. The policy is tested by simulation and
numerical examples are shown in Section 3. Conclusions are given in Section 4.
2. The Set-up Problem of Label Switched Paths
We consider a physical IP network Gph(N,L) with a set of N routers and a set of
physical links L. We define the following notation for Gph(N, L):
(cid:12)9 l(i, j) E L (cid:12)9 There exists a physical link between routers i and j.
(cid:12)9 Cph(i, j) for i, j E N" The total link capacity of l(i, j).
(cid:12)9 Aph(i,j) for i,j E N" The available capacity on l(i,j).
We introduce a virtual "induced" MPLS network G(N, s as in 3, for the physical
network Gph(N,L) . This virtual MPLS network G(N,f...) consists of the same set of
routers N as the physical network hpG (N, L) and a set of virtual links called LSPs, denoted
by s Note that G is a directed graph and/: D_ L.
We define the following notation for G(N, 2):
(cid:12)9 LSP(i, j) E f-." There exists an LSP between routers i and j.
(cid:12)9 C(i,j) for i,j E N" The total capacity of LSP(i,j) (C(i,j) - 0 r iSP(i,j) not
established).
(cid:12)9 A(i, j) for i, j E N" The available capacity on LSP(i, j).
(cid:12)9 B(i,j) for i,j E N (cid:12)9 The total bandwidth reserved between touters i and j. It
represents the total traffic between router i as the source and router j as the desti-
nation.
Each LSP must be set on an existing physical connection in Gph(N, L). We assume
that the shortest path Pph(i, j) between a source node i and destination node j is the
minimum hop path in Gph(N, L) and is denoted by
Pph(i, j) = {l(i, h),..., l(k, j) }.
In the MPLS network, the bandwidth requests between i and j are routed either on a
direct LSP(i,j) or on multiple LSPs overlaying Pph(i,j):
P(i,j)- {LSP(i,h),...,LSP(k,j)}.
Let S(i, j) be the set of all LSP(u, v) such that the corresponding shortest path ,U(hpP v)
contains the link l(i, j). The following condition must be satisfied:
C(u, v) < 5Cph(i,j). (1)
LSP(u,v)6S(i,j)
where 5 < 1 is a maximum fraction of hpC (i, j) that can be assigned to LSPs. Condition 1
means that the sum of capacity of all LSPs using a particular physical link on their path
must not exceed a portion 5 of the capacity of that physical link.
Let us define by tm the instant of arrival of the mth request for bandwidth allocation
,i(nib j) between touters i and j. Assuming a finite time horizon, let T denote the end of
the observation period and assume that there are M requests during that period.
When a new bandwidth request bm(i,j) arrives between routers i and j in the MPLS
network, the existence of a direct LSP between i and j is checked initially. For direct
LSP between i and j, the available capacity A(i,j) is then compared with the request
bm(i,j). If A(i,j) > bm(i,j), then the requsted bandwidth is allocated on that LSP and
the available capacity is reduced accordingly. Otherwise, C(i, j) can be increased subject
to condition 1 in order to satisfy the bandwidth request. If there exists no direct LSP
between i and j, then we need to decide whether to set-up a new LSP and its according
C(i,j). Each time a new LSP is set-up, the previously granted bandwidth allocation
requests between i and j are re-routed on the new LSP. However, this rerouting operation
is only virtual, since by our assumptions the physical path is maintained fixed and only
the switching technique is varied. An LSP can also be re-dimensioned/torn-down if the
available bandwidth is greater than a given threshold, after a periodic examination. The
LSPs corresponding to the physical links are never torn down.
Definition 1: Set of States
For each router pair i and j in the MPLS network, the state vector sm at the time instant
tm is defined as
sm= C(i, j), A(i, j), B(i, j), P(i, J)l" (2)
If the LSP between i and j does not exist, then sm- ,0 0, B(i,j), P(i,j). Note that at
any instant of time, the total number of state vectors is N (cid:12)9 (N- )1 where N is the set
of all routers.
Definition 2: Set of Actions
Assume that at time instant tin, a request bm(i,j) arrives. The decision of setting up or
re-dimensioning the corresponding LSP is captured by the binary action variable a, with
a = 1 meaning that the LSP will be set-up or re-dimensioned and with a - 0 meaning
that no action will be taken and the request is routed either on aq direct LSP or on the
multi-LSP physical shortest path in the MPLS network.
