Switching, Wireless, Routing, Protocols, etc.

ABSTRACT

This paper presents a new source routing technique for ring and multi-ring networks, which uses short address labels. The main objectives for having this new method are that in case of one or more failures a frame will be guaranteed: (i) to be removed from the ring - termination property, and (ii) to be copied at most once and only by its destinations - safety property.
The scheme is based on dividing the label address space of each ring into subspaces, such that the address subspaces are physically disjoint. More specifically, each ring, in a multi-ring network, is divided into two or more parts such that adjacent address subspaces are disjoint. The route of each frame is described by a sequence of short address labels in the frame's header. The current route of a frame is determined by the first address label in its header, and it can be used for routing over at most one subspace of the ring.

ABSTRACT

In networks that use label swapping routing, like ATM, inconsistent routing tables, due to either incorrect setups or memory failures, may result in infinite looping of packets. This work proposes and analyzes a method for ensuring self-termination in such networks. The method is based on imposing linear order on the labels chosen by the stations along the route during connection setup, and on a simple on-line check performed by every station upon making routing decisions. We then analyze the probability of connection setup failure due to the linear order constraint, and show that it is very small.

ABSTRACT

In computer networks there is usually a trade-off between the performance and implementation complexity of the routing protocol, and those of the protocol for reliable transmission of data. Often, the routing protocol can perform better if it is not required to retain the FIFO order of the routed data units. However, in such a case the protocol for reliable transmission of data has to maintain many logical timers and to have accurate estimate of the round trip delay. The paper introduces a new notion: semi-FIFO service, which means that the routing layer retains the FIFO order in part.

The paper shows that sometimes a non-FIFO routing layer may provide for semi-FIFO service, without substantial changes in the routing concept. Then, the paper proposes a new protocol for reliable transmission of data over an unreliable semi-FIFO routing layer. The protocol uses only one logical timer and does not require an estimate of the round trip delay in order to operate with full capacity. Therefore, the contribution of the paper is eliminating the deficiencies associated with non-FIFO routing schemes that may offer semi-FIFO service.

ABSTRACT

This paper presents a protocol and design for concurrent and reliable group multicast (many-to-many) from bursty data sources in general networks. In a group multicast, any node can be a multicast source and multiple nodes may start to multicast simultaneously, i.e., an asynchronous access to the network. The reliable multicast protocol presented in this work is window based with a combined sender and receiver initiation of the recovery protocol. In reliable multicasting the necessary requirement is to ensure that data is received correctly by all the active members of the multicast group.
The approach taken in this work is to combine the multicast operation with the internal flow control, as a result, it is possible to provide: (1) loss-free multicast routing with a single and immediate acknowledgement message to the sender. Furthermore, in every multicast, (2) a node can access all the capacity allocated to its group with no delay, however, if several nodes are active in the same group then the capacity will be shared fairly. In addition, (3) each sender in the multicast group uses a single timer, and (4) a node can join and leave a multicast group in a transparent fashion, i.e., there is no need to explicitly notify the members of the group.
A multiple criteria optimization study of the bandwidth allocation to each multicast group is presented. The optimization problem has two Min-Max objective functions: (1) for delay, which caused by the number of links needed to connect the group, and (2) for congestion, which is caused by sharing a link among multiple multicast groups. The bandwidth allocation among multicast group sharing the same link are further optimized using the Max-Min fairness criterion.

ABSTRACT

A protocol for setting up a tree connection for the purpose of multicast communication over a high-speed packet switched network is presented. The tree connection is based on the use of local identifiers, which are swapped at every intermediate node of the tree. Local identifiers are simple to manage, provide fast access to the routing tables, and are very efficient in terms of the size of the resulting routing space.
The context of this work is a high-speed network in which the local label swapping on data messages is performed in hardware by the switching subsystem, while the connection set-up is done in software by the switch control subsystem. A reliable protocol for setting up the tree connection is presented, and its correctness is formally proved. The protocol ensures the integrity of the tree and when failures occur, it is gracefully degraded into a smaller tree.

ABSTRACT

We investigate the problem of self-stabilizing round-robin token management on a bidirectional ring of identical processors. Each processor is an asynchronous probabilistic finite state (i.e., constant space) machine which sends and receives constant-size messages and whose state transition is triggered by the receipt of a message. We also show that this problem is equivalent to symmetry breaking (i.e., leader election).
We justify and suggest a two-layer (hardware and software) solution to the token management problem: The subproblem of reducing an arbitrary but nonzero number of tokens (in an otherwise arbitrary initial system state) to exactly one token (and a legal system state) is solved in hardware and takes only small polynomial time. The detection of a complete lack of tokens (communication deadlock) is done by a software clock. In high-speed networks the hardware layer can be implemented using fast universal switches (i.e., finite state machines) independent of the size of the network. We note that randomization is essential, since Dijkstra showed that for arbitrary rings the subproblem does not have a deterministic solution (regardless of the computational power of the identical processors). The use of the software layer (deadlock detection) in our solution is minimized.

ABSTRACT

One of the main challenges of today's networking is how to increase the capacity of wireless data networks. Given the inherent limitations of radio frequency (RF) transmission capacity, a promising approach is to divide the 2D/3D space into multiple subspaces and to apply spatial channel reuse, which has the potential: (1) to increase aggregate system capacity, (2) to increase the wireless transmission range, (3) to reduce signal-to-noise and signal-to-interference ratio (SNR/SIR), (4) to reduce fading and (5) to reduce power consumption. This paper focuses on how using switched-beam antenna, on mobile devices (stations), can improve wireless communications. Specifically, we study the potential benefit of using a selected one of a multiple flat panel directional antennas, where the antenna selection is performed dynamically � packet-by-packet. The initial results are promising and show significant improvements of various aspects of the wireless system performance.