Soft-state Protocol Research Articles

Analyses of soft-state signaling protocols in GMPLS-Based WDM networks

Wavelength-routed Generalized Multi-Protocol Label Switching (GMPLS) networks use Resource reSerVation Protocol—Traffic Engineering (RSVP-TE) as signaling protocol to set up and tear down lightpaths. RSVP-TE uses a soft-state control mechanism to manage lightpaths. In the soft-state control mechanism, each node sets a timer for each control state and resets the timer with refresh messages to maintain the state. When the timer expires due to losses of refresh messages, the control state is initialized and a reserved resource managed with the state is released. It has been considered that resource utilization of soft-state protocols is inferior to that of hard-state protocols, since soft-state protocols may reserve resources until control states are deleted due to timeout. Therefore, some extensions to promote the performance of soft-state protocols, such as message retransmission, have been considered. In this paper, we analyze the behavior of GMPLS RSVP-TE and its variants with a Markov model and analyze the performance of RSVP-TE. From the results, we demonstrate that resource utilization of RSVP-TE can be equivalent to that of a hard-state protocol when the loss probability of signaling messages is low. We also investigate the effectiveness of message retransmission and show that using message retransmission leads to poor resource utilization in some cases. Copyright © 2012 John Wiley & Sons, Ltd.

Adaptive Timer-Based Countermeasures against TCP SYN Flood Attacks

SUMMARY As a result of the rapid development of the Internet in recent years, network security has become an urgent issue. Distributed denial of service (DDoS) attacks are one of the most serious security issues. In particular, 60 percent of the DDoS attacks found on the Internet are TCP attacks, including SYN flood attacks. In this paper, we propose adaptive timer-based countermeasures against SYN flood attacks. Our proposal utilizes the concept of soft-state protocols that are widely used for resource management on the Internet. In order to avoid deadlock, a server releases resources using a time-out mechanism without any explicit requests from its clients. If we change the value of the timer in accordance with the network conditions, we can add more flexibility to the soft-state protocols. The timer is used to manage the resources assigned to half-open connections in a TCP 3-way handshake mechanism, and its value is determined adaptively according to the network conditions. In addition, we report our simulation results to show the effectiveness of our approach.

The Globus Replica Location Service: Design and Experience

Distributed computing systems employ replication to improve overall system robustness, scalability, and performance. A replica location service (RLS) offers a mechanism to maintain and provide information about physical locations of replicas. This paper defines a design framework for RLSs that supports a variety of deployment options. We describe the RLS implementation that is distributed with the Globus toolkit and is in production use in several grid deployments. Features of our modular implementation include the use of soft-state protocols to populate a distributed index and Bloom filter compression to reduce overheads for distribution of index information. Our performance evaluation demonstrates that the RLS implementation scales well for individual servers with millions of entries and up to 100 clients. We describe the characteristics of existing RLS deployments and discuss how RLS has been integrated with higher-level data management services.

A Study of Control Plane Stability with Retry Traffic: Comparison of Hard- and Soft-State Protocols

SUMMARY Recently problems with commercial IP telephony systems have been reported one after another, in Japan. One of the important causes is congestion in the control plane. It has been recognized that with the current Internet it is important to control not only congestion caused by overload of the data plane but also congestion caused by overload of the control plane. In particular, “retry traffic,” such as repeated attempts to set up a connection, tends to cause congestion. In general, users make repeated attempt to set up connections not only when the data plane is congested but also when the control plane in the network is overloaded. The latter is caused by user behavior: an increase in the waiting time for the processing of connection establishment to be completed tends to increase his or her initiation of reattempts. Thus, it is important to manage both data plane and control-plane resources effectively. In this paper, we focus on RSVP-based communication services including IP telephony, and introduce a model that takes account of both data-plane and control-plane systems, and we examine the behavior of retry traffic. In addition, we compare the system stability achieved by two different resource management methods, the hard-state method and the soft-state method.

Modelling soft-state protocols with SDL

The notion of soft state has been introduced in packet-switched networks to achieve particular services for end-to-end communications, such as quality-of-service provisioning and configuration of stateful packet filters. Protocols built upon soft state principles were believed to be simple, however in practice they are far more complex. An important issue with such protocols is to ensure their operations to be error-free and deadlock-free. In the paper the use of formal techniques is proposed, specifically, Specification and Description Language (SDL) and Message Sequence Charts (MSCs), for modelling, analysis and validation of soft-state protocols. Based on a general state management system that identifies their most representative behaviour, an extensive study on modelling and validating soft-state protocols with SDL/MSCs is presented, and it is shown that design flaws and ambiguity introduced in informally specified, textual protocols can be avoided if a protocol is formally modelled.