“Hitless protection switching method for passive optical network”
Hiromi UEDA, Toshinori TSUBOI, and Hiroyuki KASAI
Abstract – The Passive Optical Network (PON) shares transmission facilities to provide broadband services economically. To enhance network survivability, ITU-T Rec. G.983.5 defines some protection switching methods. These methods, however, always bring about signal loss when switching is performed. Moreover, a network operator often has to replace one optical fiber cable with another that takes a different route due to constructions like social infrastructure renewal. If hitless switching is available, the operator can carry out that activity anytime without impacting users, and can also offer higher-grade broadband services. Thus the hitless protection technology for PON systems is very attractive and useful. This paper proposes hitless switching methods for PON systems based on the PON’s unique features. We also present a specific hitless protection method for GE-PON as a design example.
“An analysis of loop formation in OLSRv2 in ad-hoc networks and limiting its negative impact”
Lee SPEAKMAN, Yasunori OWADA, and Kenichi MASE
Abstract – Transient routing loops have been observed to form in Ad-hoc Networks running the OLSRv2 routing protocol. The looping traffic significantly increases the impact on the surrounding network and its traffic thus degrading end-to-end transmission by a significant factor even though only a small proportion of the traffic may enter these loops and only for a brief time. This becomes significantly more evident when Link Layer Notification is used to catch broken links, inadvertently leading to the increase in loops. The ways in which these loops form and why Link Layer Notification significantly increases the number of loops is analyzed. Two methods of Loop Detection is introduced in this paper and used in combination with Packet Discard to selectively and preemptively discard those packets that are unlikely to reach their destination and are contributing to the load on the network. The effect of this Loop Suppression is to negate the detrimental effects on surrounding traffic and is found to improve network performance significantly.
“Implementation experiments of TCP Symbiosis: bio-inspired mechanisms for Internet congestion control”
Mizuho KODAMA, Go HASEGAWA, and Masayuki MURATA
Abstract – In this paper, we investigate the performance of a Linux implementation of a new congestion control mechanism for TCP, TCP Symbiosis. Whereas the traditional TCP Reno recognizes the network congestion only by detecting packet losses, TCP Symbiosis directly obtains the information of physical capacity and available bandwidth of the network path between sender and receiver hosts, and utilize an algorithm based on the mathematical models from biophysics to regulate the congestion window size. The proposed mechanism controls the sending rate by bandwidth information and therefore it can avoid self-induced packet losses on bottleneck links. We implement the proposed mechanism on Linux kernel system and investigate the performance through experiments using the public Internet