A fundamental problem in quality-of-service (QoS) routing is to find a path between a source- destination node pair that satisfies two or more end-to-end QoS constraints. We model this problem using a graph with n vertices and edges with K additive QoS parameters associated with each edge, for any constant K ≥ 2. This problem is known to be NP-hard. Fully polynomial time approximation schemes (FPTAS) for the case of K = 2 have been reported in the literature. We concentrate on the general case and make the following contributions. 1) We present a very simple O(Km + n log n) time K-approximation algorithm that can be used in hop-by-hop routing protocols. 2) We present an FPTAS for one optimization version of the QoS routing problem with a time complexity of O(m (n/ε)K-1). 3) We present an FPTAS for another optimization version of the QoS routing problem with a time complexity of O(n log n + m (H/ε)K-1) when there exists an H-hop path satisfying all QoS constraints. When K is reduced to 2, our results compare favorably with existing algorithms. The results of this paper hold for both directed and undirected graphs. For ease of presentation, undirected graph is used.
- Efficient approximation algorithms
- Multiple additive constraints
- QoS routing
ASJC Scopus subject areas
- Computer Science Applications
- Computer Networks and Communications
- Electrical and Electronic Engineering