Electrical computers and digital processing systems: multicomput – Computer-to-computer protocol implementing – Computer-to-computer data transfer regulating
Reexamination Certificate
2000-01-24
2004-07-06
Dharia, Rupal (Department: 2141)
Electrical computers and digital processing systems: multicomput
Computer-to-computer protocol implementing
Computer-to-computer data transfer regulating
C709S238000, C709S226000
Reexamination Certificate
active
06760774
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a boundary apparatus for controlling the connection between communication networks and, more particularly, to a boundary apparatus for mapping a resource reservation protocol (e.g., RSVP) in an ATM network for the purpose of controlling the quality of communication in an IP network (Internet Protocol Network) in the network structure in which the ATM network exists between a transmitting terminal in an IP network and a receiving terminal in another IP network, and the method of controlling the connection by the boundary apparatus.
2. Description of the Related Art
(a) Guarantee of Quality in an Internet
Recently, internets have been rapidly developing owing to the improvement and expansion of applications. Especially, owing to the image and sound superposing technique and the hyperlinkage technique which have been realized in a www (world wide web), internets have been developing as a communication means which becomes more accessible and which gives a feeling that the correspondents are actually conversing face to face. On the other hand, the problem of delay in communication in a network has become remarkable. One reason is that an appropriate means or technique does not catch up with the increase in the traffic, but the root cause is that internets are based on the best-effort transfer system which transfers IP packets with the best effort.
In the transfer circumstance of the best-effort system, the best efforts are directed only on transferring the packet which has arrived to the next stage without discriminating the packet by the user or the application, and the packets which can not be transferred, for example, the packets which overflow the buffer are discarded as they are. The discarded packets are detected at the end terminal by a TCP (Transmission Control Protocol) which is upper on the IP layer, and retransmitted, thereby avoiding discard. The retransmission, however, leads to some evils. For example, unnecessary packets stay in the network, and the prevention of a delay in the transfer is not guaranteed to a real-time application.
In order to eliminate these problems, the method of realizing the QoS (Quality of Service) has been investigated by the IETF (Internet Engineering Task Force), and the QoS control technique in the IP layer based on the RSVP (Resource Reservation Protocol) version 1 was already standardized and the study has been continued toward the realization thereof.
(b) Resource Reservation Protocol in an Internet
An RSVP is a control protocol for resource reservation in an IP layer, and exerts the control shown in FIG.
62
. In this control, control messages (Path message, Reserve message) are transmitted and received between a router
2
which supports an RSVP on IP network
1
and a sender
3
of information (transmitting terminal), and between the router
2
and a receiver
4
(receiving terminal). Due to the control, memory resource and the like within the transmission path and the router
2
are reserved for the application of the sender
3
, and the quality of communication is guaranteed. Generally, the sender
3
is able to provide the same information for a plurality of receivers
4
by point-multipoint communication (multicast).
The sender
3
first transmits a Path message containing traffic characteristics of the contents which are delivered to the receivers
4
. The Path message is transferred along the routers
2
and distributed into a plurality of receivers
4
. Each of the receivers
4
returns a Reserve message containing the resource which requires reservation to the sender
3
by reference to the contents of the Path message. The router
2
on the way merges the requests for reservation sent from the plurality of receivers
4
and transfers the Reserve message to the router
2
on the upper stream and the sender
3
, and reserves the transmission path (bandwidth) and the memory resource for the receivers
4
.
The mechanism of bandwidth reservation by the RSVP will be schematically described in the following. This mechanism is based on RFC2205 (Resource Reservation Protocol (RSVP)-Version 1 Functional Specification).
In the RSVP, the data flow to a specified destination and a transport layer protocol is defined as a session. The destination of a certain session (data flow) is generally defined by DestAddress. The DestAddress corresponds to the IP destination address which is written on the IP header potion of an IP packet. The process of bandwidth reservation consists of the following steps 1 to 4. It is here assumed that all of the transmitting terminal (sender host), the receiving terminals (receiver host) and the nodes (routers) on the path mount the RSVP.
(1) Establishment of Session
A route is set between the transmitting terminal and each of the receiving terminals by a certain routing protocol. The receiving terminals join a multicast group which is determined by the DestAddress according to an IGMP (Internet Group Multicast Protocol) or the like.
(2) Transmission of a Path Message
The transmitting terminal periodically transmits a Path message to the route (i.e., each DestAddress) established by the routing protocol. The Path message contains information on the data transmitted from the transmitting terminal, for example, IP address, traffic characteristics, and the IP address of the previous Hop to the transmitting terminal, as will be described later in detail.
Each node on the path holds the information on the transmitting terminal and the session as a Path state on the basis of the information in the Path message, and when the node receives a new Path message, it updates the Path state in accordance with the contents thereof and transfers the updated Path state to the next Hop (node). Similar operations are repeated thereafter, and the Path message ultimately reaches all the receiving terminals.
(3) Transmission of a Reserve Message
Each receiving terminal transmits a message for resource reservation (Reserve message) to the transmitting terminal. The Reserve message is transmitted to the Previous IP address (the IP address of the HOP on the upper stream) which is held in the Path state of each node. As will be described later, the Reserve message contains the QoS information which is required by the receiving terminal, the information on the form of bandwidth reservation, the IP address of the node to which the Reserve message is transmitted (i.e., the previous IP address), etc.
(4) Processing by Each Node which has Received a Reserve Message
The RSVP controller of each node which has received Reserve message reserves a bandwidth. The RSVP controller holds the reservation information as a reservation state on the basis of the QoS information, the information on the form of bandwidth reservation, etc. required in the message. The RSVP controller also merges the reservation state from each route, and holds the merged information for finally reserving the bandwidth as a traffic control state.
The RSVP controller requires the traffic controller of the node to reserve the bandwidth on the basis of the traffic control state information. The admission control section of the traffic controller judges whether or not the required QoS is to be accepted. That is, whether or not the required QoS is to be accepted is determined in accordance with whether or not a bandwidth corresponding to the required QoS is vacant. If the acceptance is possible, the admission control section secures the bandwidth in accordance with the contents of the required reservation, and the RSVP controller transmits the Reserve message to the node of the previous IP address which is recorded in the Path state of its own node. On the other hand, if the acceptance is impossible, the RSVP controller discards the Reserve message and transmits an error message to the receiving terminal which has transmitted the Reserve message.
(c) RSVP Message
(c-1) Path message
FIG. 63
is an explanatory view of the format of a Path message.
The Path message PATH contains parameters which are
Ezaki Yutaka
Nakamichi Koji
Soumiya Toshio
Takashima Kenya
Watanabe Naotoshi
Dharia Rupal
Nguyen Quang
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