Łukasz Budzisz

Research Fellow

Hamilton Institute
National University of Ireland (NUI) Maynooth
Maynooth, Kildare

Tel.:     +353 1 708-6273
Fax:     +353 1 708-6269
E-mail: lukasz(dot)budzisz[at]nuim(dot)ie

Short bio

I was born in Zgierz, Poland. In 2003, I received the M.Sc. degree in Electronics and Telecommunication from the Technical University of Lodz (PL), Poland. I was awarded two grants, one from the Generalitat de Catalunya (FI) in  2004, and one from the Spanish Ministry of Education (FPU) in 2005-2008, for my Ph.D. work in the Mobile Communication Research Group (GRCM) in the Department of Signal Theory and Communication (TSC) at the Universitat Politecnica de Catalunya (UPC) in Barcelona, Spain. During my Ph.D. studies I did two short-term research visits. In 2006, I was a visiting scholar to the Department of Computer Science, Karlstad University, Sweden, and in 2007, to the Protocol Engineering Labs (PEL) at the University of Delaware, USA. I completed my Ph.D. in 2008. From October 2008 I started working as a research fellow at the Hamilton Institute, NUI Maynooth in Ireland.
[Full biography]

Research interests

Congestion control

Congestion control in TCP/IP networks is traditionally handled using packet losses to indicate congestion [1]. This approach, called loss based congestion control, proved to be working well over more than 20 years. However, recent improvements in communication technologies, and popularisation of wireless, high speed, and more generally, links with high bandwidth delay product (BDP), has exposed various shortcomings of loss-based congestion control. The main criticism, apart from the increased loss rate is linked to unefficient link utilisation and significant variations in network delay.

An alternative approach to respond to congestion involves the use of network delay (delay based congestion control). This was first proposed by Jain already in 1989 [2] and since then, there has been much work and debate on this topic. Delay-based congestion control is conceptually very attractive. Potential benefits include the ability to allocate the network bandwidth between competing sources with: (i) low (zero) packet loss; (ii) very low queueing delay; and (iii) with full utilisation of network links. Networks which exhibit this property are said to operate at the knee of the throughput-delay curve [3]. Motivated by these and other potential benefits, delay-based congestion control remains an active area of research and new algorithms continue to be developed. Recent examples include: Fast TCP [4]; Microsoft Compound [5] (partially based on delay); and more recent delay-based additive increase multiplicative decrease (AIMD) variants [6-9].

Despite this large body of work, several issues concerning the use of queueing delay remain to be resolved before delay based congestion control can be deployed. These include: (i) the difficulty in obtaining delay estimates from network measurements [10]; (ii) network sampling issues [10–13]; (iii) the inability of existing delay-based algorithms to maintain a low standing queue [12, 13]; and (iv) the inability of delay-based flows to coexist fairly with loss-based flows in mixed environments. Our novel design Coexistant TCP (C-TCP) tries to tackle one of the biggest unresolved problems of the delay-based congestion control, namely, the coexistence problem. [More...]

[1] V. Jacobson, “Congestion avoidance and control,” in SIGCOMM’88: Symposium proceedings on Communications architectures and protocols. New York, NY, USA: ACM, 1988, pp. 314–329.
[2] R. Jain, “A delay-based approach for congestion avoidance in interconnected heterogeneous computer networks,” ACM Comp. Commun. Rev., vol. 19, no. 5, pp. 56–71, 1989.
[3] R. Jain and K. Ramakrishnan, “Congestion avoidance in computer networks with a connectionless network layer: concepts, goals and methodology,” Computer Networking Symposium, pp.134–143, 1988.
[4] J. Wang, D. X. Wei, and S. Low, “Modelling and stability of FAST TCP,” in Proc. of the 24th IEEE INFOCOM Conference, vol. 2, 2005, pp. 938– 948.
[5] K. Tan, J. Song, Q. Zhang, and M. Sridharan, “A compound TCP approach for high-speed and long distance networks,” 2005, Technical Report - Microsoft Research MSR-TR-2005-86.
[6] D. Leith, J. Heffner, R. Shorten, and G. McCullagh, “Delay-based AIMD congestion control,” in Proc. of the 5th Int’l Workshop on Protocols for FAST Long-Distance Networks (PFLDnet), 2007.
[7] D. Leith, R. Shorten, G. McCoullagh, L. Dunne, and F. Baker, “Making available base RTT for use in congestion control applications,” IEEE Commun. Lett., vol. 12, no. 6, pp. 429–431, June 2008.
[8] S. Bhandarkar, A. Reddy, Y. Zhang, and D. Loguinov, “Emulating AQM from end hosts,” SIGCOMM Comput. Commun. Rev., vol. 37, no. 4, pp. 349–360, October 2007.
[9] K. Kotla and A. Reddy, “Making a delay-based protocol adaptive to heterogeneous environments,” in Proc. of the 16th International Workshop on Quality of Service (IWQoS 2008), June 2008, pp. 100–109.
[10] J. Martin, A. Nilsson, and I. Rhee, “Delay-based congestion avoidance for TCP,” IEEE/ACM Trans. Netw., vol. 11, no. 3, pp. 356–369, June 2003.
[11] R. Prasad, M. Jain, and C. Dovrolis, “On the effectiveness of delay-based congestion avoidance,” in Proc. of the 2nd Int’l Workshop on Protocols for FAST Long-Distance Networks (PFLDnet), 2004.
[12] G. McCullagh, “Exploring delay based TCP congestion control,” Master’s thesis, Hamilton Institute, NUI Maynooth, Ireland, 2008.
[13] C. Kellett, R. Shorten, and D. Leith, “A review of delay-based congestion control,” 2006, Cisco Report - Distributed to project partners, March 2006.

Stream Control Transmission Protocol (SCTP)

The Stream Control Transmission Protocol (SCTP) was first announced in October 2000 in the, now an obsolete, RFC 2960.  Current protocol specification is defined in the RFC 4960.  SCTP provides a reliable, full-duplex connection with flow and congestion control algorithms that are derived from TCP, thus following the same Additive Increase Multiplicative Decrease (AIMD) behavior. An SCTP connection is called association, and is established using a four-way handshake (instead of a three-way handshake as in TCP) in order to improve protocol security and make it resistant to blind denial of service (DoS) attacks (such as flooding and masquerade). What made SCTP a subject of considerable interest however, are two new features it introduces: multihoming and multistreaming.

Multihoming (illustrated above) binds multiple source-destination IP addresses for a single association between two SCTP endpoints. These IP addresses are exchanged and verified during the association setup, and each destination transport address is considered as a different path towards the corresponding endpoint. Multihoming in SCTP was originally designed to increase the robustness of the signalling environments. Consequently, the scope of use for multihoming defined within the RFC 4960 is only for handling single retransmissions and perfor
ming primary path failover in case of a permanent link failure. Any other applications, e.g., transport-layer handover or loadsharing over multiple network paths, are not supported within the standard SCTP specification, and instead should be covered by dedicated protocol extensions (e.g., transport-layer handover application of multihoming requires Dynamic Address Reconfiguration (DAR) SCTP extension, defined in the RFC 5061). Regardless of this limitation, SCTP multihoming seems a promising protocol feature that may easily be leveraged to provide support for both mentioned applications.

Multistreaming, the second of the new SCTP features (illustrated above), allows the establishment of associations with multiple streams. Streams are unidirectional data flows within a single association. The number of requested streams is declared during the association setup and the streams are valid during the entire association lifetime. Each stream is distinguished with the Stream Identifier field included in each chunk (SCTP packet consist of a common header and one or more chunks), so that chunks from different streams can be bundled inside one SCTP PDU. To preserve order within a  stream the Stream Sequence Number (SSN) is used. Consequently, TCP’s HoL blocking problem stalling entire TCP connection is reduced to the affected SCTP stream only, as data received in order within a stream (handled by SSN) but not within the entire association (counted using TSN) can be delivered to the application. Among the most important applications of multistreaming are priority stream scheduling, preferential treatment, and reducing the latency of streaming multimedia in high-loss environments.

An exhaustive collection of all SCTP-related research can be found here [SCTP survey].

Mobility management

Next generation mobile data networks are expected to achieve a high degree of inter-networking so that the mobile users can truly experience seamless access to their services, irrespective of the radio technology being used. In such scenarios, IP networking is becoming the keystone capable to turn this vision into a reality. Hence, mobility management solutions for IP networks are expected to provide seamless mobility across multiple radio access options. Earlier works on the mobility management problem discussed various solutions, mainly in network and application layer of the ISO/OSI protocol stack. More recently, transport layer handover schemes emerged, and are currently receiving a notable attention in the research community, as they seem to match very well the basic paradigm of the IP networking, where intelligence is moved towards the edges of the network.

My Ph.D. dissertation, and all mobility related articles, evaluate the concept of seamless handover management at the transport layer (in particular SCTP protocol) in IP-based heterogeneous wireless networks, as well as introduce a cross-layer design, and concurrent multipath transfer to optimize such a handover process.


Congestion control

[1] Delay based congestion control for heterogeneous environments,
Ł. Budzisz, R. Stanojevic, A. Schlotte, R. Shorten and F. Baker
submitted to IEEE/ACM Transactions on Networking magazine, under evaluation.
 For more results see [here]

[2] On the fair coexistence of loss- and delay-based TCP
Ł. Budzisz, R. Stanojevic, A. Schlotte, R. Shorten and F. Baker
Proc. of the 17th International Workshop on Quality of Service (IWQoS 2009),
Charleston, SC, United States, July 2009.
[3] A strategy for fair coexistence of loss and delay-based congestion control algorithms
Ł. Budzisz, R. Stanojevic, R. Shorten and F. Baker
IEEE Communications Letters, vol. 13, no. 7, p. 555-557, July 2009.

Mobility management

[1] A taxonomy and survey of SCTP research
Ł. Budzisz, J. Garcia, A. Brunstrom, and R. Ferrús
submitted to ACM Computing Surveys magazine, under evaluation.

[2] On Concurrent Multipath Transfer in SCTP-based handover scenarios
Ł. Budzisz, R. Ferrús, F. Casadevall, and P.Amer
Proc. of IEEE International Conference on Communications, 2009 (ICC '09),
Dresden, Germany, June 2009. 
[3] Design principles and performance evaluation of mSCTP-CMT for transport-layer based handover
Ł. Budzisz, R. Ferrús, and F. Casadevall
Proc. of the 69th IEEE Vehicular Technology Conference (VTC 2009-Spring),
Barcelona, Spain, April 2009. 

Towards transport-layer mobility: Evolution of SCTP multihoming
Ł. Budzisz, R. Ferrús, A. Brunstrom, R. Grinnemo, K.-J. Fracchia, G. Galante, and F. Casadevall
Computer Communications, vol. 31, no. 5, pp. 980–998, March 2008
An analytical estimation of the failover time in SCTP multihoming scenarios
Ł. Budzisz, R. Ferrús, K.-J. Grinnemo, A. Brunstrom, and F. Casadevall
Proc. of IEEE Wireless Communications and Networking Conference (WCNC 2007), pp. 3932–3937,
Hong Kong, March 2007. 
SCTP multihoming performance in dynamically changing channels with the influence of link-layer retransmissions
Ł. Budzisz, R. Ferrús, and F. Casadevall
Proc. of the 64th IEEE Vehicular Technology Conference (VTC 2006-Fall), pp. 2624–2628,
Montreal, Canada, September 2006.
On the performance of multihoming SCTP in dynamically changing radio channels
Ł. Budzisz, R. Ferrús, and F. Casadevall
Proc. of the 15th International Mobile Summit (IST 2006),
Mykonos, Greece, June 2006.

Study on transport layer handover using SCTP
Ł. Budzisz, R. Ferrús, and F. Casadevall
Proc. of the 8th International Symposium on Wireless Personal Multimedia Communications
(WPMC 2005)
Aalborg, Denmark, September 2005.

Network simulation and emulation tools

NMLab: A Co-Simulation Framework for Matlab and ns-2
O. Heimlich, R. Sailer, and Ł. Budzisz
accepted to the 2nd International Conference on Advances in System Simulation (SIMUL 2010).
Nice, France, August 2010.

Evaluation of Perceived QoS with Multimedia Applications in a Heterogeneous Wireless Network
N. Vucevic, F. Bernardo, A. Umbert, and Ł. Budzisz
Proc. of the 4th International Symposium on Wireless Communication Systems (ISWCS 2007), pp. 102-106,
Trondheim, Norway, October 2007. 
A beyond 3G real-time testbed for an All-IP heterogeneous network
F. Bernardo, N. Vucevic, Ł. Budzisz, and A. Umbert
Proc. of the 5th ACM International Workshop on Mobility Management and Wireless Access
(MOBIWAC 2007), pp. 50-59
Chania, Crete Island, Greece, October 2007.

An all-IP heterogeneous wireless testbed for RAT selection and e2e QoS evaluation
A. Umbert, Ł. Budzisz, F. Bernardo, and N. Vucevic
Proc. of the 1st International Conference on Next Generation Mobile Applications, Services and Technologies (NGMAST 2007), pp. 310-315,
Cardiff, Wales, September 2007. 

A Performance Evaluation Framework of A Rate-Controlled MPEG Video Transmission over UMTS Networks
N. Akar, M. Barbera, Ł. Budzisz, R. Ferrús, E. Kankaya, and G. Schembra
Proc. of the 12th IEEE Symposium on Computers and Communications (ISCC 2007),
pp. MW 63 - MW 68
Aveiro, Portugal, July 2007. 


version 1.1,

© Lukasz Budzisz, 17 June 2010