Multiplex communications – Wide area network – Packet switching
Patent
1994-11-14
1996-09-10
Hsu, Alpus H.
Multiplex communications
Wide area network
Packet switching
370 601, 370 61, 370 856, H04L 1256
Patent
active
055552641
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND
The present invention is related to methods and devices for prioritizing procedures when handling buffers in packet networks, in particular methods and devices for loss prioritizing and delay prioritizing of data packets.
In packet oriented networks, e.g. ATM (Asynchronous Transfer Mode), data packets or message packets, also called cells, are forwarded between different stations and in particular they pass through switch units or other units, where the arrived packets are forwarded. These transferring stations (most often switches) contain memories or buffers which store the packets before they are forwarded. However the buffers have limited capacities and thus in such systems some method is provided for eliminating certain data package for which there is no space in the buffers.
In order to determine the packets which can be discarded when there is no room in a buffer, the data packets can be assigned loss priorities having different sizes. They are principally a number value indicating the importance of the packet, such that packets having low loss priorities can be eliminated before packets having higher loss priorities.
In such networks it would also be advantageous to have a method by means of which the different data packets are forwarded in such a way that data packets having a high degree of urgency are forwarded in the first place and that data packets having a low degree of urgency in the second place. The degree of urgency can be indicated by assigning to the data packets delay priorities having different values which like the loss priorities are suitably chosen number values. In certain cases several levels having different delay priorities may be provided. The simplest type of queue handling is that first packets are forwarded having the highest priorities and after that, if there are no data packets left in the buffer for the highest priority, data packets having lower priorities can be forwarded. A disadvantage in this procedure may be that messages having low priorities may be allowed to wait too long in the system before they are forwarded.
Thus it would be desirable to have a method by means of which it can be safeguarded, that also for data packets having low degrees of priority a certain minimal capacity in the transfer thereof in the system is warranted.
Further it is advantageous to separate the above mentioned concepts "loss priority" and "delay priority" from each other, such that each data packet thus has both a certain loss priority and a certain delay priority.
In the article "Overload Control in a Finite Message Storage Buffer", San-Qi Li, IEEE Transactions on Communications, Vol. 37, No. 12, December 1989 a method is analyzed for handling a limited buffer memory. In an example, see page 1332, lines 30-36 and other places, there is a buffer having K places and two levels L.sub.1, L.sub.2, where L.sub.1 .ltoreq.L.sub.2 .ltoreq.K. For filling levels below L.sub.1 all messages are always stored, while when the filling level is increasing all messages having low priorities are not stored but are discarded first when the filling level exceeds L.sub.2. After this all messages are discarded having low priorities until the filling level has decreased to L.sub.1. Apparently also messages having high priorities must be discarded when the filling level is equal to K.
In the European Patent Application EP-A2 0 393 898 a device is provided having a memory for storing data packets having different priority levels. With each priority level a corresponding threshold level is associated. When a packet arrives to be stored in the memory, the packet is discarded, if the filling level exceeds the threshold level associated with the priority level of the packet. Otherwise the data packet is stored in the memory. The memory is cyclic and of type FIFO. It means that in such a device which may be a packet switch it is impossible to also take different delay priorities in the received packet into consideration, such that stored data packets having high delay priorities can be forwarded befo
REFERENCES:
patent: 5130978 (1992-07-01), Mobasser
patent: 5267232 (1993-11-01), Katsube et al.
patent: 5278530 (1994-01-01), Kudo
patent: 5278828 (1994-01-01), Chao
patent: 5359592 (1994-10-01), Corbalis et al.
patent: 5361252 (1994-11-01), Sallberg et al.
patent: 5390176 (1995-02-01), Schoute et al.
Blaabjerg Soren
Sallberg Hans K. M.
Hsu Alpus H.
Telefoanktiebolaget LM Ericsson
LandOfFree
Methods and devices for prioritizing in handling buffers in pack does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Methods and devices for prioritizing in handling buffers in pack, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Methods and devices for prioritizing in handling buffers in pack will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1326615