Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
1999-10-08
2004-04-13
Pham, Chi (Department: 2663)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S410000
Reexamination Certificate
active
06721272
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to computer networks, and relates more specifically to a method and apparatus for initiating an RSVP resource reservation process for a traffic flow originating from a network device that is not enabled to do so itself. More specifically, the present invention relates to generating an RSVP PATH message for such a traffic flow.
BACKGROUND OF THE INVENTION
A computer network typically comprises a plurality of interconnected entities that transmit (“source”) or receive (“sink”) data frames. A common type of computer network is a local area network (“LAN”) that generally comprises a privately owned network within a single building or campus. LANs employ a data communication protocol (LAN standard) such as Ethernet, FDDI, or Token Ring, that defines the functions performed by the data link and physical layers of a communications architecture (i.e., a protocol stack), such as the Open Systems Interconnection (OSI) Reference Model. In many instances, multiple LANs may be interconnected by point-to-point links, microwave transceivers, satellite hookups, etc., to form a wide area network (“WAN”), metropolitan area network (“MAN”) or Intranet. These internetworks may be coupled through one or more gateways to the global, packet-switched internetwork known as the Internet.
Each network entity preferably includes network communication software, which may operate in accordance with Transport Control Protocol/Internet Protocol (TCP/IP) or some other suitable protocol. A protocol generally consists of a set of rules defining how entities interact with each other. In particular, TCP/IP defines a series of communication layers, including a transport layer and a network layer. At the transport layer, TCP/IP includes both the User Data Protocol (UDP), which is a connectionless transport protocol, and TCP which is a reliable, connection-oriented transport protocol. When a process at one network entity (source) wishes to communicate with another entity, it formulates one or more messages and passes them to the upper layer of the TCP/IP communication stack. These messages are passed down through each layer of the stack where they are encapsulated into packets and frames. Each layer also adds information in the form of a header to the messages. The frames are then transmitted over the network links as bits. At the destination entity, the bits are re-assembled and passed up the layers of the destination entity's communication stack. At each layer, the corresponding message headers are also stripped off, thereby recovering the original message which is handed to the receiving process.
One or more intermediate network devices are often used to couple LANs together and allow the corresponding entities to exchange information. For example, a bridge may be used to provide a “bridging” function between two or more LANs. Alternatively, a switch may be utilized to provide a “switching” function for transferring information, such as data frames or packets, among entities of a computer network. Typically, the switch is a computer having a plurality of ports (i.e., logical network interfaces (“LI” or “interfaces)) that couple the switch to several LANs and to other switches. The switching function includes receiving data frames at a source port and transferring them to at least one destination port for receipt by another entity. Switches may operate at various levels of the communication stack. For example, a switch may operate at Layer
2
which, in the OSI Reference Model, is called the data link layer, and includes the Logical Link Control (LLC) and Media Access Control (MAC) sub-layers.
Other intermediate devices, commonly known as routers, may operate at higher communication layers, such as Layer
3
, which, in TCP/IP networks, corresponds to the Internet Protocol (IP) layer. IP data packets include a corresponding header which contains an IP source address and an IP destination address. Routers or Layer
3
switches may re-assemble or convert received data frames from one LAN standard (e.g., Ethernet) to another (e.g., Token Ring). Thus, Layer
3
devices are often used to interconnect dissimilar subnetworks. Some Layer
3
intermediate network devices may also examine the transport layer headers of received messages to identify the corresponding TCP or UDP port numbers being utilized by the corresponding network entities. Many applications are assigned specific, fixed TCP and/or UDP port numbers in accordance with Request For Comments (RFC) 1700. For example, TCP/UDP port number 80 corresponds to the Hypertext Transport Protocol (HTTP), while port number 21 corresponds to File Transfer Protocol (FTP) service.
QUALITY OF SERVICE (QoS)
The processes executing at network entities (e.g., Internet hosts) may generate hundreds or thousands of traffic flows that are transmitted across a network. Generally, a traffic flow is a set of messages (frames and/or packets) that typically correspond to a particular task, transaction, or operation (e.g., a print transaction), may be associated with an application, and may be identified by various network and transport parameters such as source and destination IP addresses, source and destination TCP/UDP port numbers, and transport protocol.
Computer networks typically include numerous services and resources for use in moving traffic flows throughout the network. For example, different network links, such as Fast Ethernet, Asynchronous Transfer Mode (ATM) channels, network tunnels, satellite links, etc., offer unique speed and bandwidth capabilities. Particular intermediate devices also include specific resources or services, such as number of priority queues, filter settings, availability of different queue selection strategies, congestion control algorithms, etc. Each port/logical network interface (LI) of a network device can provide a different service or resource. For ease of explanation, the term “network device,” unless expressly stated otherwise, herein refers to the device in its entirety or one or more ports/LIs.
To maximize the transit performance of a traffic flow across a network, a desired quality of service (QoS) can be requested. For a given traffic flow, a desired QoS can be designated for each of various aspects of the traffic flow treatment across the network (i.e., how various services and resources of the network interact with the traffic flow as it travels across the network).
RESERVATION OF NETWORK RESOURCES
To obtain desired qualities of service (QoS), mechanisms can be used to reserve resources across a network along a path between a source and destination of a traffic flow. For example, the Resource Reservation Protocol (RSVP) provides a mechanism by which such resource reservations can be made. When both the source and destination are capable of utilizing RSVP (i.e., RSVP-enabled), the source generates and sends a PATH message along an intended path to the destination (i.e., intended receiver). The PATH message can specify the various characteristics of the traffic flow that is to be sent. The destination device can then establish the resource reservation in RSVP-enabled network devices along the intended path by sending back a RESV message. Additional information regarding RSVP can be found, for example, in
Internetworking Technologies Handbook
, Macmillan Technical Publishing (1998). The RSVP mechanism can be used with multicast or unicast traffic flows. The discussions herein are equally applicable to both with suitable modification.
Some sources of traffic flows are not designed, or are otherwise unable to start a reservation process with a PATH message as discussed above. For example, the source may be non-RSVP-enabled, not trusted, or merely designed or utilized so as not to bear the burden of handling the issue. RSVP signaling can require a large and complex protocol stack, with heavy demands on the source with respect to the memory footprint, O/S capabilities, and CPU load. By not including appropriate capabilities on network devices, the cost of such devices can be mi
Mohaban Shai
Parnafes Itzhak
Cisco Technology Inc.
George Keith M.
Hickman Palermo & Truong & Becker LLP
Pham Chi
LandOfFree
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