New models and algorithms for programmable networks Danny Raz a, * ,1 , Yuval Shavitt b,1 a Computer Science Faculty, Technion––Israel Institute of Technology, Haifa 32000, Israel b Department of Electrical Engineering––Systems, Tel Aviv University, Tel Aviv 69978, Israel Abstract In todays IP networks most of the network control and management tasks are performed at the end points. As a result, many important network functions cannot be optimized due to lack of sufficient support from the network. The growing need for quality guaranteed services brought on suggestions to add more computational power to the network elements. This paper studies the algorithmic power of networks whose routers are capable of performing complex tasks. It presents a new model that captures the hop-by-hop datagram forwarding mechanism deployed in todays IP networks, as well as the ability to perform complex computations in network elements as proposed in the active networks para- digm. Using our framework, we present and analyze distributed algorithms for basic problems that arise in the control and management of IP networks. These problems include: route discovery, message dissemination, multicast, topology discovery, and bottleneck detection. Our results prove that, although adding computation power to the routers increases the message delay, it shortens the completion time for many tasks. The suggested model can be used to evaluate the contribution of added features to a router, and allows the formal comparison of different proposed architectures. Ó 2002 Published by Elsevier Science B.V. Keywords: Active networks; Distributed computing; Network management 1. Introduction The design of todays IP networks is based on the end-to-end argument, that calls for the internal network elements to concentrate on the simple forwarding function, leaving the network control and management to the end points. As a result, many important network functions cannot be op- timized due to lack of sufficient support from the network. To alleviate this problem, in many pro- posed architectures the network elements are en- hanced with more processing abilities. Active networks [14,18] are an extreme example of the break away from the end-to-end argument [1]. In these networks even the forwarding and routing functions may be done in software. This paper studies the algorithmic power of networks whose elements, namely routers, are capable of per- forming complex tasks. We use the term active networks in this paper to relate to any such net- work. Computer Networks 38 (2002) 311–326 www.elsevier.com/locate/comnet * Corresponding author. Tel.: +972-4-829-4938; fax: +972-4- 822-1128. E-mail addresses: danny@cs.technion.ac.il (D. Raz), shavitt@ eng.tau.ac.il (Y. Shavitt). 1 This work was done while the authors were with Bell Labs, Lucent Technologies, Holmdel, NJ. 1389-1286/02/$ - see front matter Ó 2002 Published by Elsevier Science B.V. PII:S1389-1286(01)00290-0