Excavating – Cable-operated – Boom-type
Reexamination Certificate
2002-09-03
2003-08-26
Vanderpuye, Ken (Department: 2661)
Excavating
Cable-operated
Boom-type
C370S395100
Reexamination Certificate
active
06609316
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a node device for transferring packets by attaching priority information, a node device for processing packets attached with priority information, and a packet transfer method using priority information attached to packets.
2. Description of the Background Art
A mechanism for guaranteeing QoS (Quality of Service) in IP (Internet Protocol) network has been proposed in a form of providing a constant QoS with respect to individual TCP/UDP session, based on an approach disclosed in R. Braden, L. Zhang, S. Berson. S. Herzog and S. Jamin, “Resource ReSerVation Protocol (RSVP)—Version I Functional Specification”, Internet RFC 2205, September 1997; J. Wroclawski, “Specification of the Controlled-Load Network Element Service”, Internet RFC 2211, September 1997; and S. Shenker, C. Partridge and R. Guerin, “Specification of Guaranteed Quality of Service”, Internet RFC 2212, September 1997. However, this approach has been associated with a problem of scalability because it is necessary for each router of the network to maintain a state with respect to individual session so that it has been considered rather difficult to employ this approach in a large scale network.
Instead, there is a proposition of a framework called Differentiated Service (DS). The goal of DS is provide a mechanism in which the quality of service can be changed according to an amount of money paid by a user as simply as possible. At the data transfer level, a TOS (Type Of Service) field of the packet header is used in order to distinguish different QoSs, rather than having a state for each session in the network.
As for the priority bit to be used in the TOS field, there are a scheme for using just one bit as disclosed in D. Clark and J. Wroclawski, “An Approach to Service Allocation in the Internet”, Internet Draft, draft-clark-diff-svc-alloc-00.txt, July 1997, and a scheme for using plural bits as disclosed in K. Kilkki, “Simple Integrated Media Access (SIMA)”, Internet Draft, draft-kalevi-simple-media-access-01.txt, June 1997.
The basic scheme of DS is as follows. A subscribed rate is specified between a user and a network or between two neighboring management networks (domains), and packets are marked as high priority packets while the transmission rate is less than or equal to the subscribed rate, or as low priority packets when the transmission rate exceeds the subscribed rate, according to a relationship between the subscribed rate and the monitored packet transmission rate. Then, the high priority packets are handled with priority over the low priority packets within the network or domain so as to provide different QoSs. Here, the marking is done by attaching (writing) an information indicating the priority level to the packet.
In the present specification, the subscribed rate between a user and a network will be referred to as an edge level rate (ELR) and the subscribed rate between two neighboring domains will be referred to as a domain level rate (DLR).
FIG. 1
shows an exemplary network to which DS is applied. In
FIG. 1
, U
1
, U
2
and U
3
are users (user terminals or user networks), E
1
and E
2
are edge routers, B
1
, B
2
, B
3
, B
4
, B
5
and B
6
are domain border routers, and R
1
is a relay router.
FIG. 1
shows a case involving four domains A, B, C and D. For instance, a network managed by one ISP (Internet Service Provider) corresponds to one domain.
Suppose that users U
1
, U
2
and U
3
in the domain A have subscribed edge level rates (ELR) of 2 Mbps, 2 Mbps and 5 Mbps, respectively, with respect to the domain A. In
FIG. 1
, only the subscribed rate for one direction is indicated for the sake of simplicity but it is possible to have the subscribed rate for both directions. It is assumed that the user is allowed to carry out the marking of high/low priority levels with respect to transmission packets at will. The edge routers E
1
and E
2
measure the arrival rate of the transmission packets from the user, and marks those high priority packets that arrived at rate above the subscribed edge level rate as low priority ones.
Then, suppose that the domain level rate (DLR) of 5 Mbps has been subscribed for traffic passing from the domain A to the domain B, for example. In
FIG. 1
, only the subscribed rate for one direction is indicated for the sake of simplicity but it is possible to have the subscribed rate for both directions. The domain border router B
2
measures the arrival rate of packets from the domain A, and marks those high priority packets that arrived from the domain border router B
1
at rate above the DLR as low priority ones. Similarly, when the DLR of 2 Mbps has been subscribed for traffic passing from the domain B to the domain C, the domain border router B
5
marks those high priority packets that arrived from the domain border router B
3
at rate above the DLR as low priority ones. Also, when the DLR of 10 Mbps has been subscribed for traffic passing from the domain B to the domain D, the domain border router B
6
marks those high priority packets that arrived from the domain border router B
4
at rate above the DLR as low priority ones.
Now, consider the case of using only one bit of the priority bit in FIG.
1
. In this case, both the edge routers and the domain border routers will rewrite the same priority bit at a time of marking.
When the receiving rate of the high priority packets is above the subscribed rate at the domain level, the high priority packets below the subscribed rate will be passed as they are while packets above the subscribed rate will be marked as low priority ones regardless of whether they are originally high priority ones or low priority ones.
Suppose now that the user U
1
transmitted the high priority packets destined to a host in the domain C at the ELR value of 2 Mbps. Also suppose that no transmission packets other than those from the user U
1
are flowing from the domain border router B
3
to the domain border router B
5
. Then, if the total transmission rate of the high priority packets from the users U
2
and U
3
is less than or equal to 3 Mbps, all the high priority packets from the user U
1
will be delivered to the domain C as they are.
However, if the users U
2
and U
3
also transmit the high priority packets to the domain D and the total transmission rate of the high priority packets from the users U
2
and U
3
exceeds 3 Mbps, a part of the high priority packets from the user U
1
will be changed into the low priority packets. In this case, there is a problem in that these high priority packets from the user U
1
which are changed into the low priority packets at the domain border router B
2
will be handled as the low priority ones in the domain C as well even if the domain border router B
5
of the domain C has enough margin to pass 2 Mbps of the high priority packets from the user U
1
.
This problem is also present in the case of using plural priority bits as long as the same plural bits are to be rewritten at both the edge level and the domain level similarly as in the case of using one priority bit.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a mechanism for a packet transfer scheme that applies markings at different levels to packets while they are transferred from their source to destination, in which a marking information at one level will not be lost by a marking at another level.
In order to achieve this object, the present invention provides a plurality of regions to which the priority information can be attached in a packet in correspondence to the plural levels, such that a region corresponding to one level will not be rewritten by a node that carries out the marking at another level.
A node device according to the present invention is thus characterized by writing the priority information according to criteria of the own node into a region in a packet into which the own node is allowed to write the priority information among the plurality of regions to which the priority information can be wri
Ohba Yoshihiro
Shimojo Yoshimitsu
LandOfFree
Node device and packet transfer method using priority in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Node device and packet transfer method using priority in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Node device and packet transfer method using priority in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3097439