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Loop-Free Updates of Forwarding Tables
KTH, School of Electrical Engineering (EES), Communication Networks.
KTH, School of Information and Communication Technology (ICT), Communication: Services and Infrastucture, Telecommunication Systems Laboratory, TSLab.ORCID iD: 0000-0002-3172-076X
KTH, School of Electrical Engineering (EES), Communication Networks.ORCID iD: 0000-0002-3704-1338
2008 (English)In: IEEE Transactions on Network and Service Management, ISSN 1932-4537, Vol. 5, no 1, 22-35 p.Article in journal (Refereed) Published
Abstract [en]

When the forwarding paths in an IP network change due to a link failure or a link weight modification, the forwarding tables in the routers may need to be updated. Each of these updates may cause transient loops if they are not performed in an appropriate order. In this paper, we propose an order to update the forwarding tables that avoids transient loops for non-urgent changes. The order is obtained by studying the changes in the forwarding tables, therefore it can be used in networks running any routing protocols, and for any type of forwarding path changes. After presenting the order, we prove that it is correct, and present an efficient algorithm to compute the order. Thereafter, we present several algorithms for performing forwarding table updates in accordance with the order. We also discuss how the update algorithms can be applied to both networks with centralized control and decentralized routing protocols. Finally, we study the update algorithms’ performance on several network topologies and with varying parameter settings and for several types of forwarding path changes.

Place, publisher, year, edition, pages
2008. Vol. 5, no 1, 22-35 p.
Keyword [en]
Configuration management; FIB updates; Network management; Transient routing loops
National Category
URN: urn:nbn:se:kth:diva-9328DOI: 10.1109/TNSM.2008.080103ScopusID: 2-s2.0-49049121685OAI: diva2:113509
QC 20100726Available from: 2008-10-30 Created: 2008-10-20 Last updated: 2013-09-09Bibliographically approved
In thesis
1. On the Design of Next-Generation Routers and IP Networks
Open this publication in new window or tab >>On the Design of Next-Generation Routers and IP Networks
2008 (English)Doctoral thesis, comprehensive summary (Other scientific)
Abstract [en]

This thesis investigates distributed router architectures and IP networks with centralized control. While the current trend in IP-router architectures is towards decentralized design, there have also been research proposals for centralizing the control functions in IP networks. With continuous evolution of routers and IP networks, we believe that eventually IP networks in an autonomous system (AS) and a distributed router might converge into one network system. This system, which can be considered both as a distributed router and a centrally-controlled IP network, is divided into a control plane and a forwarding plane. The control plane is responsible for routing, management and signalling protocols, while the forwarding plane is responsible for forwarding packets.

The work in this thesis covers both the forwarding and control planes. In the forwarding plane, we study network processor systems that function as forwarding elements in a distributed router. We introduce a system model and a simulation tool based on the model. Using the simulation tool, we investigate network processor system design by studying throughput, utilization, queueing behavior and packet delays. In addition to network processor systems, we study IP-address lookup, which is one of the key packet processing functions in Internet routers. Our work in IP-address lookup contains an efficient lookup algorithm, a scheme to divide the lookup procedure into two-stages in a distributed router, and an approach to perform efficient lookup on a router supporting multiple virtual routers.

In the control plane, we study three emerging research issues with centralized control. We provide a thorough study of the routing convergence process in networks with centralized control, and compare it with decentralized link-state routing protocols. We propose an efficient approach to perform traffic engineering and routing in networks with centralized control, and compare it with an approach using optimized link weights. Finally, we present an approach to perform loop-free updates of forwarding tables when the forwarding paths change. This loop-free update approach is particularly useful in networks with centralized control.

The results presented in this thesis are useful for building next-generation routers and IP networks with centralized control that might eventually converge into one network system.

Place, publisher, year, edition, pages
Stockholm: KTH, 2008. vii, 34 p.
Trita-EE, ISSN 1653-5146 ; 2008:040
router architecture, IP-network architecture
National Category
urn:nbn:se:kth:diva-9381 (URN)
Public defence
2008-11-26, M1, KTH, Stockholm, 14:00 (English)
QC 20100726Available from: 2008-11-03 Created: 2008-10-28 Last updated: 2010-07-26Bibliographically approved

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