Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1999-08-24
2003-05-13
Kizou, Hassan (Department: 2662)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S401000, C370S466000
Reexamination Certificate
active
06563794
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a boundary device for mapping a resource reservation protocol intended to perform a communication quality control in an Internet Protocol (IP) network within a network configuration where an Asynchronous Transfer Mode (ATM) network exists between a sending terminal in one IP network and a receiving terminal in another IP network, and a method thereof.
2. Description of the Related Art
In recent years, the Internet being a communications network among computers has been making rapid progress with an increasing number of IP applications. Especially, the Internet has been advancing as a communications tool which is easier to use and realizes strong feelings of presence with the superposition of video and voice data and use of hyperlinks, which are realized by the WWW (World Wide Web).
Fundamentally, each node independently determines the route of an IP packet referred to as a datagram not by establishing a connection, but by making an end-to-end negotiation in an IP network. In a communications network performing such connectionless communications, data packets are normally routed and transferred for each hop (hop-to-hop transfer).
However, with the progress of the Internet, a network delay problem becomes more and more serious. One reason may be that a transfer means or a technique cannot catch up with an increase in network traffic. The principal cause, however, is the fact that the Internet is on the basis of a best-effort transfer.
Under a best-effort transfer environment where IP packets are transferred with the best effort, a repeater station at which packets arrive does not makes a distinction between the packets depending on users or applications, and only makes an effort to transfer the arrived packets to the next stage. Packets which cannot be transferred and overflow from a buffer are discarded.
Packet discarding is detected by a TCP (Transmission Control Protocol) higher than an IP layer at an end station, and is prevented by a retransmission procedure. However, there are problems in that packets not required for retransmission stay in a network, and that a transfer delay is not guaranteed for a real-time application.
To overcome such problems, a method for implementing the QOS (Quality Of Service) on the Internet was discussed in the IETF (Internet Engineering Task Force). A QOS control technique in an IP layer, which is based on the Version
1
of an RSVP (Resource Reservation Protocol), was standardized, and its implementation method has been studied up to now.
The RSVP is a control protocol for making a resource reservation in an IP layer, and performs the control shown in FIG.
1
A. Under this control, control messages are exchanged between routers
2
supporting the RSVP in an IP network
1
, an information sender (sending terminal)
3
, and a receiver (receiving terminal)
4
. With the exchange of the control messages, memory resources, etc. on a transmission line or within a router are reserved beforehand for an application of the sender
3
, and its communication quality (QOS) is guaranteed. Normally, the sender
3
can provide the same information to a plurality of receivers
4
with a one-to-multiple communication. First of all, the sender
3
sends to the receiver
4
a Path message describing the traffic characteristic of information (contents) to be sent. The Path message is transferred along a transfer route (via routers), and distributed to each receiver
4
.
The receiver
4
returns to the sender
3
a resource reservation message (Reserve message) describing a resource for which a reservation is required by referencing the contents described in the Path message. An intermediate router
2
merges reservation requests from a plurality of receivers
4
, transfers the merged request to an upstream router
2
or the sender
3
, and reserves transmission lines or memory resources for the plurality of receivers
4
.
Next, the outline of a resource reservation mechanism using the RSVP is explained. The following explanation is based on the “RSVP (Resource ReSerVation Protocol)—Version 1 Functional Specification” of the RFC (Request for Comments) 2205.
With the RSVP, a data flow for a particular destination and a transport layer protocol is defined as a session. A destination in a certain session is normally defined by “DestAddress”. This corresponds to an IP destination address of a data packet.
The procedure for making a resource reservation is composed of the following steps (1) through (4). Here, all of a sending terminal (sending side host), a receiving terminal (receiving side host), and nodes (routers) on a path are assumed to comprise the RSVP.
(1) Session establishment: a route between a sending and a receiving terminal is established by some routing protocol or other. Additionally, the receiving terminal joins a multicast group stipulated by the “DestAddress” according to an IGMP (Internet Group Multicast Protocol), etc.
(2) Path message transmission: a sending terminal periodically sends a Path message to a route established by a routing protocol (that is, to each DestAddress). The Path message describes the IP address of a sender, the information about the data such as a traffic characteristic, etc., which are sent by the sending terminal, and the IP address of a previous hop.
Each of the nodes on the path stores as a path state the information about the sending terminal and its session based on the information included in the Path message. Upon receipt of the Path message, each of the nodes updates its path state according to the contents of the Path message, and transfers the Path message to the next hop (node). Eventually, the Path message reaches all of receiving terminals.
(3) Resv message transmission: each of the receiving terminals sends a Resv message to the sending terminal. The Resv message is sent to a previous IP address (on an upstream side) stored in the path state of each of the nodes. This Resv message describes the QOS information requested by a receiving terminal, the information about a bandwidth reservation format, or the IP address of the destination node to which the Resv message is sent (that is, the previous IP address), etc.
(4) Process performed by each of the nodes receiving the Resv message: an RSVP controlling unit within each of the nodes, which has received the Resv message, makes a bandwidth reservation. The RSVP controlling unit stores reservation information as a reservation state based on the QOS information, the information about the bandwidth reservation format, etc. within the Resv message. Additionally, the RSVP controlling unit considers (merges) the reservation states obtained from respective routes, and finally stores the information for reserving a bandwidth as a traffic control state.
The RSVP controlling unit requests a traffic controlling unit within each of the nodes to reserve a bandwidth based on the information of the traffic control state. The traffic controlling unit comprises an admission controlling unit, which determines whether or not the requested QOS can be admitted. If this QOS can be admitted, a bandwidth is secured according to the contents of the reservation request. At this time, the Resv message is sent to the previous IP address stored in the path state of the corresponding node. If the QOS cannot be admitted, the Resv message is discarded and an error message is sent to the receiving terminal.
As a communications network having a form different from that of an IP network which performs such a communication quality control, an ATM network exists. The ATM is a transfer technique that is formed into specification by the ITU-T (International Telecommunication Union-Telecommunication Standardization Sector), etc. as a solution to a future broadband ISDN (Integrated Services Digital Network).
Originally, the ATM was intended to perform an efficient transfer and cost-effective network management regardless of media types by uniformly handling all services with short cells of fixed-length packets (of 53
Ezaki Yutaka
Murata Kazunori
Nakamichi Koji
Soumiya Toshio
Takashima Kenya
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