Automatically applying bi-directional quality of service treatment to network data flows

[0002] The present invention generally relates to data processing in a network communication system. The invention relates more specifically to methods and apparatus that provide automatic bi-directional quality of service treatment to network data flows.

[0003] 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 knows as Internet.

[0004] Each network entity preferably includes network communication software, which may operate in accordance with Transport Control Protocol/Internet Protocol (TCP/IP). TCP/IP 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 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 reassembled 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.

[0005] 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 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.

[0006] 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.

[0007] Computer networks include numerous services and resources for use in moving traffic 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.

[0008] Individual frames or packets can be marked so that intermediate devices may treat them in a predetermined manner. For example, the Institute of Electrical and Electronics Engineers (IEEE) describes additional information for the MAC header of Data Link Layer frames in Appendix 802.1p to the 802.1D bridge standard.

[0009] FIG. 1A is a partial block diagram of a Data Link frame 100 that includes a MAC destination address (DA) field 102, a MAC source address (SA) field 104 and a data field 106. According to the 802.1Q standard, a user_priority field 108, among others, is inserted after the MAC SA field 104. The user_priority field 108 may be loaded with a predetermined value (e.g., 0-7) that is associated with a particular treatment, such as background, best effort, excellent effort, etc. Network devices, upon examining the user_priority field 108 of received Data Link frames 100, apply the corresponding treatment to the frames. For example, an intermediate device may have a plurality of transmission priority queues per port, and may assign frames to different queues of a destination port on the basis of the frame's user priority value.

[0010] FIG. 1B is a partial block diagram of a Network Layer packet 120 corresponding to the Internet Protocol. Packet 120 includes a type_of_service (ToS) field 122, a protocol field 124, an IP source address (SA) field 126, an IP destination address (DA) field 128 and a data field 130. The ToS field 122 is used to specify a particular service to be applied to the packet 120, such as high reliability, fast delivery, accurate delivery, etc., and comprises a number of sub-fields. The sub-fields may include a 3-bit IP precedence (IPP) field and three one-bit flags that signify Delay, Throughput, and Reliability. By setting the flags, a device may indicate whether delay, throughput, or reliability is most important for the traffic associated with the packet. Version 6 of the Internet Protocol (Ipv6) defines a traffic class field, which is also intended to be used for defining the type of service to be applied to the associated packet.

[0011] A working group of the Internet Engineering Task Force (IETF) has proposed replacing the ToS field 122 of Network Layer packets 120 with a one-octet differentiated services (DS) field 132 that can be loaded with a differentiated services codepoint (DSCP). Layer 3 devices that are DS compliant apply a particular per-hop forwarding behavior to data packets based on the contents of their DS fields 132. Examples of per-hop forwarding behaviors include expedited forwarding and assured forwarding. The DS field 132 is typically loaded by DS compliant intermediate devices located at the border of a DS domain, which is a set of DS compliant intermediate devices under common network administration. Thereafter, interior DS compliant devices along the path apply the corresponding forwarding behavior to the packet 120.

[0012] FIG. 1C is a partial block diagram of a Transport Layer packet 150 that preferably includes a source port field 152, a destination port field 154, and a data field 156, among others. Fields 152, 154 preferably are loaded with the TCP or UDP port numbers that are utilized by corresponding network entities.

[0013] To interconnect dispersed computer networks, many organizations rely on the infrastructure and facilities of Internet Service Providers (ISPs). For example, an organization may lease one or more T1 lines to interconnect various LANs. Each organization enters into a service-level agreement with its ISP. The service level agreements include one or more traffic specifications. The traffic specifications may place limits on the amount of resources that the organization may consume for a given price.

[0014] For example, an organization may agree not to send traffic that exceeds a certain bandwidth, e.g., 1 Mb/s. Traffic entering the service provider's network is monitored to ensure that it complies with the relevant traffic specifications and is thus “in profile.” Traffic that exceeds a traffic specification, and is therefore “out of profile,” may be dropped or shaped or may cause an accounting change. Alternatively, the service provider may mark the traffic as exceeding the traffic specification, but allow it to proceed through the network anyway. If there is congestion, an intermediate network device may drop such marked traffic first in an effort to relieve the congestion.

[0015] A process executing at a network entity 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) 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.

[0016] The treatment that is applied to different traffic flows may vary depending on the particular traffic flow at issue. For example, an online trading application may generate stock quote messages, stock transaction messages, transaction status messages, corporate financial information messages, print messages, data backup messages, etc. A network administrator may wish to apply a different policy or service treatment (“quality of service” or “QoS”) to each traffic flow. In particular, the network administrator may want a stock quote message to be given higher priority than a print transaction. Similarly, a $1 million stock transaction message for a premium client should be assigned higher priority than a $100 stock transaction message for a standard customer.

[0017] Quality of service signaling mechanisms, such as RSVP and DiffServ (or IP Precedence) can be used by network applications to signal the network and get specific treatment for specific flows. However, such mechanisms only permit one-directional quality of service signaling, from the sender to the receiver. This is inadequate for many applications.

[0018] Consider as an example, an Internet Service Provider (ISP) that is handling video conference traffic from a server at the ISP to a remote client. When a video conference connection is established between the ISP's equipment and the client, the ISP can set quality of service values for the outbound data flow that are appropriate to video conference traffic. However, processes for causing equipment in a remote network that contains the client to know that it is receiving video conference traffic, and for causing it to set quality of service values appropriately for traffic sent from the client to the server, are complex. These processes also do not scale well.

[0019] For example, if the client is connected through many edge network elements, then an appropriate QoS command must be configured on each and every edge network element. The classification of the flow may be dynamic so there is no way to preconfigure the edge devices to apply the right treatment to the other side's flow. Further, even if the classification is static (e.g., based on the IP address of the server), it may scale poorly. If there are many servers, one must potentially place a command for each and every server on potentially each and every edge device. This requires an unreasonable amount of work.

[0020] Further, applications may run on hosts that have no inherent capability of setting quality of service values. In a network with such hosts, quality of service signaling is carried out by a network device that serves as a proxy for quality of service. The proxy, for example, generates RSVP messages on behalf of the application, or marks its packets using a pre-installed Access Control List (ACL). In some cases, the receiving device is not under the same control as the sending device, or there is no proxy, or there may be many receiving devices. In all these cases, establishing signaling for a flow in the reverse direction is complicated.

[0021] For example, in a one-to-many configuration, such as a server with many clients, in one current approach, current approaches may require configuring multiple ACLs on multiple edge devices. Some approaches might require configuring many different ACLs on each and every switch; potentially one ACL for each server for quality of service is required. This requires extensive, duplicative configuration work.

[0022] Another context presenting problems for current approaches is an ISP network, for example, an ISP network that provides virtual private network services, in which a first peer node is within the network and a second peer node is outside the network. The ISP may mark traffic outbound from the first node, for example, by creating and storing an appropriate ACL on the switch or router that is adjacent to the first node. However, for each such node the ISP would have to install a similar ACL on all network devices at the border or edge of the network and going into other ISPs. Further, these ACLs might need to be added and removed dynamically as network flows are created and stopped.

[0023] Based on the foregoing, there is a clear need in this field for a way to set quality of service values for packets transmitted in the network flow in both directions of a flow among a sender and a receiver.

[0024] There is a specific need for an approach whereby QoS may be established for a flow at a single network edge device and automatically enforced by all other edge devices, without separate, manual configuration work occurring at all the edge devices. Current approaches do not permit automatic, bi-directional application of quality of service values to network data flows in this manner.

[0025] There is a specific need for a mechanism, useful for a data flow that is carrying a bi-directional or symmetrical video conference call, with which quality of service values may be set for devices used only in the outbound route of the data flow.

[0026] The foregoing needs, and other needs and objects that will become apparent from the following description, are fulfilled by the present invention, which comprises, in one embodiment, a method of providing automatic bi-directional quality of service treatment of a network data flow. A network device located at the edge or border of a network, such as a router that is connected to another network, identifies incoming data flows that have packets set with quality of service treatment values. The quality of service treatments recognized by the network device may be IP precedence, DSCP marking of packets in the flow, an RSVP PATH message, etc. Upon identifying an inbound flow with quality of service treatment, the network device creates and stores, in its local memory, values that uniquely identify the flow and that tell the device how to treat packets of the same flow that are transmitted in the opposite or outbound direction. All packets of the same flow, regardless of flow direction with respect to the network device, are given a pre-configured quality of service treatment.

[0027] In one aspect, the invention provides a method of automatically applying a quality of service treatment to a network data flow, comprising the steps of receiving a network data flow comprising at least one message element that is associated with an outbound quality of service treatment value; creating and storing an inbound quality of service value in association with information identifying the network data flow; receiving one or more inbound message elements; determining that the inbound message elements are associated with the same network data flow; and applying the inbound quality of service value to the inbound message elements based on the stored information.

[0028] According to one feature, receiving a network data flow comprises receiving a network data flow comprising at least one message element that is marked with a DSCP value and wherein applying the inbound quality of service value comprises marking the inbound message elements with the DSCP value. A related feature is that receiving a network data flow comprises receiving a network data flow comprising one or more message elements that are marked with a DSCP value, and wherein applying the inbound quality of service value comprises retrieving the inbound quality of service value from a mapping of DSCP values to associated quality of service values, and adding the retrieved quality of service value to the inbound message elements.

[0029] In another feature, the creating and storing step comprises creating and storing a hash entry in a hash table that uniquely identifies the network data flow and that includes the inbound quality of service value.

[0030] Still another feature is that applying the inbound quality of service value to the inbound message elements based on the stored information comprises automatically generating an inbound RSVP PATH message for the flow when the inbound message elements include an RSVP PATH message. Yet another feature is that receiving a network data flow comprises receiving a network data flow comprising at least one message element that includes an RSVP PATH message, and applying the inbound quality of service value comprises marking the inbound message elements with an RSVP PATH message.

[0031] Other features and aspects will become apparent from the following description and claims.

[0032] The present invention is illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings and in which like reference numerals refer to similar elements and in which:

[0033] FIG. 1A is a partial block diagram of a Data Link frame.

[0034] FIG. 1B is a partial block diagram of a Network Layer packet.

[0035] FIG. 1C is a partial block diagram of a Transport Layer packet.

[0036] FIG. 2 is a block diagram of a network system configured for automatic bi-directional quality of service treatment of network data flows.

[0037] FIG. 3 is a block diagram of a flow diagram of an exemplary embodiment of a method of automatic bi-directional quality of service treatment of network data flows.

[0038] FIG. 4 is a block diagram of a computer system with which an embodiment may be used.

[0039] A method and apparatus providing automatic bi-directional quality of service treatment of network data flows is described. In the following description, for the purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures and devices are shown in block diagram form in order to avoid unnecessarily obscuring the present invention.

[0040] In one embodiment, a network device located at the edge or border of a network, such as a router that is connected to another network, identifies data flows coming from within its network that have packets set with quality of service treatment values. The quality of service treatments recognized by the network device may be IP precedence, DSCP marking of packets in the flow, an RSVP PATH message, etc. Upon identifying an outbound flow with quality of service treatment, the network device creates and stores, in its local memory, a set of data values that uniquely identify the flow and that tell the device how to treat packets of the same flow that are transmitted back into the network. All packets of the same flow, regardless of flow direction with respect to the network device, automatically are given a pre-configured quality of service treatment. The stored data values may comprise any information sufficient to uniquely identify a flow, e.g., values indicating source IP address, destination IP address, source port, destination port, and protocol. The quality of service treatment that is automatically applied may be the same as that first identified, or may be a function of that treatment.

[0041] FIG. 2 is a block diagram of a communications system. A local area network 200 comprises network end stations 202 that are coupled to the network 200 and to router 204. Each network end station 202 is an end station or terminal device such as a workstation, personal computer, printer, etc. Router 204, in one preferred embodiment, is a router of the type used in packet-switched data networks. For example, any router in the model 2600 series, commercially available from Cisco Systems, Inc., San Jose, Calif., may be used as router 204. Switch 206 connects router 204 to network 208, which is another local area network, a wide area network, or the global, packet-switched internetwork known as the Internet.

[0042] The configuration of network 200 is shown only as a representative example of the kind of network that can be used in an embodiment. Any number of routers, end stations, and switches may be used in other suitable networks.

[0043] For purposes of illustrating an exemplary embodiment, in this configuration, network 200 functions as a sending network. Thus, one of the network end stations 202 initiates a network data flow, comprising a stream of message elements, directed toward another end station elsewhere in the network. The stream of message elements may comprise, in a preferred embodiment, packetized data, for example, a transmission over a TCP/IP connection to a remotely located server.

[0044] Network 208 is further coupled to a receiving network 211. In one embodiment, which is illustrated as an example, network 211 comprises firewall 210, which is coupled to a network device 212 that is coupled to an automatic quality of service treatment element 220 and a local hash table 214. Router 216 is coupled to other end stations 218 within network 211. In this configuration, end stations 202 may send information through the networks to end stations 218. The information is sent in the form of individually switched message elements such as packets.

[0045] In a preferred embodiment, the network device 212 is a router, switch, or gateway that is located at the edge or border of a network. For example, network device 212 may be a router that is connected to another network, as in FIG. 2, or a switch that is connected directly to servers, etc.

[0046] Automatic quality of service treatment element 220 may be implemented in the form of one or more computer software elements, programs, processes or instructions that provide automatic reverse-direction or bi-directional quality of service treatment of network data flows. In a preferred embodiment, automatic quality of service treatment element 220 comprises program instructions that are integrated into a network operating system that is executed by network device 212. An example of a suitable network operating system is Internetworking Operating System (IOS) release 12, commercially available from Cisco Systems.

[0047] Network device 212 may be, for example, a router or a switch of the type used in packet-switched data networks. Preferably, network device 212 is located at the edge or border of a network, such as a router that is connected to another network, a switch that is connected directly to servers, etc., as seen in FIG. 2.

[0048] In operation, network device identifies incoming flows that have quality of service treatment. The quality of service treatment recognized by the network device may be IP precedence, DSCP marking of packets in the flow, an RSVP PATH message, etc. A packet may be identified as belonging to the same flow by examining values of its source IP address, destination IP address, source port number, destination port number, and protocol.

[0049] Upon identifying a flow with quality of service treatment, the network device creates and stores a value that tells the device how to treat packets of the same flow that are transmitted in the opposite direction. All packets of the same flow are given a predetermined quality of service treatment. The specific treatment that is applied may be the same. Alternatively, the specific treatment applied in the opposite direction is a function of what is applied in the original direction. For example, in the case of RSVP, the reservation used in the opposite direction may be different; this could occur, e.g., when each side of a voice conversation uses a different kind of CODEC device.

[0050] The stored information may be a hash table entry, or an entry in an access control list.

[0051] For example, an RSVP PATH message will be generated for the opposite flow. In the case of RSVP the decision may be made to either generate a reservation request (a PATH message) on the opposite direction, that is, with the same network resources request, or use other mechanisms such as DiffServ. When the inbound flow uses DiffServ or IP Precedence, network device 212 may install policy information on itself that tells itself what DSCP value to assign for the opposite flow. Generally the DSCP value assigned for the opposite flow is identical to the original value, thus putting the opposite flow into the same service class.

[0052] FIG. 3 is a flow diagram of a method of applying bi-directional quality of service treatment to network data flows. For purposes of illustrating one exemplary embodiment, the steps of FIG. 3 indicate steps that could be carried out by a device in the position of router 212 that has automatic bi-directional quality of service element 220.

[0053] In block 302, inbound message elements that are marked with an inbound quality of service value are received. For example, a router configured to execute the process of FIG. 3 receives inbound packets that are marked with DSCP values or associated with an RSVP PATH message. Block 302 may involve both determining that a quality of service value is associated with the inbound packets and determining what specific type of quality of service value is associated with the packets. The quality of service treatment recognized by the network device may be IP precedence, DSCP marking of packets in the flow, an RSVP PATH message, etc. A packet may be identified as belonging to the same flow by examining values of its source IP address, destination IP address, source port number, destination port number, and protocol.

[0054] In block 304, the process stores a quality of service value in association with information identifying the network data flow. As indicated by block 305, the steps of block 304 may involve using a local hash table to store the information. Each hash table entry comprises a combination of information identifying the network flow (such as, in the TCP/IP context, source and destination IP address values and source and destination port values), and information identifying what quality of service value to apply. Alternatively, the stored information may be an entry in an access control list.

[0055] In block 306, outbound message elements are received. Block 306 may involve receiving data packets from one of the clients 218 at router 212 that are associated with a flow directed from receiving network 211 to sending network 200.

[0056] In block 308, the process tests whether the outbound message elements are part of a known flow. Block 308 may involve obtaining information identifying the current flow that contains the message elements and looking it up in the hash table or the access control list. In the case of RSVP, such a lookup is not necessarily needed; the opposite PATH message can be generated as soon as the incoming PATH message arrives. In this case, the flows are then treated using the regular RSVP enforcement scheduling and queuing mechanisms of the router, so the process need not examine each packet. If a lookup is carried out and the information is found, then the outbound message elements are part of a known flow. If so, then control passes to block 310, in which the process retrieves a quality of service value for the current flow. Further, the process applies the quality of service value to the message elements of the current flow. If an outbound element is not part of a known flow, then no further processing is done. In the case of RSVP, a reverse PATH message can be issued without waiting, as soon as the original PATH message is received. Thus, reverse direction packets are simply forwarded and a reservation for them will have been installed and the packets will receive the preferred service.

[0057] FIG. 4 is a block diagram that illustrates a computer system 400 upon which an embodiment of the invention may be implemented. The preferred embodiment is implemented using one or more computer programs running on a network element such as a router device. Thus, in this embodiment, the computer system 400 is a router.

[0058] Computer system 400 includes a bus 402 or other communication mechanism for communicating information, and a processor 404 coupled with bus 402 for processing information. Computer system 400 also includes a main memory 406, such as a random access memory (RAM), flash memory, or other dynamic storage device, coupled to bus 402 for storing information and instructions to be executed by processor 404. Main memory 406 also may be used for storing temporary variables or other intermediate information during execution of instructions to be executed by processor 404. Computer system 400 further includes a read only memory (ROM) 408 or other static storage device coupled to bus 402 for storing static information and instructions for processor 404. A storage device 410, such as a magnetic disk, flash memory or optical disk, is provided and coupled to bus 402 for storing information and instructions.

[0059] A communication interface 418 may be coupled to bus 402 for communicating information and command selections to processor 404. In one embodiment, interface 418 is a conventional serial interface such as an RS-232 or RS-422 interface. An external terminal 412 or other computer system connects to the computer system 400 and provides commands to it using the interface 414. Firmware or software running in the computer system 400 provides a terminal interface or character-based command interface so that external commands can be given to the computer system.

[0060] A switching system 416 is coupled to bus 402 and has an input interface 414 and an output interface 419 to one or more external network elements. The external network elements may include a local network 422 coupled to one or more hosts 424, or a global network such as Internet 428 having one or more servers 430. The switching system 416 switches information traffic arriving on input interface 414 to output interface 419 according to pre-determined protocols and conventions that are well known. For example, switching system 416, in cooperation with processor 404, can determine a destination of a packet of data arriving on input interface 414 and send it to the correct destination using output interface 419. The destinations may include host 424, server 430, other end stations, or other routing and switching devices in local network 422 or Internet 428.

[0061] The invention is related to the use of computer system 400 for the techniques and functions described herein in a network system. According to one embodiment of the invention, such techniques and functions are provided by computer system 400 in response to processor 404 executing one or more sequences of one or more instructions contained in main memory 406. Such instructions may be read into main memory 406 from another computer-readable medium, such as storage device 410. Execution of the sequences of instructions contained in main memory 406 causes processor 404 to perform the process steps described herein. One or more processors in a multi-processing arrangement may also be employed to execute the sequences of instructions contained in main memory 406. In alternative embodiments, hard-wired circuitry may be used in place of or in combination with software instructions to implement the invention. Thus, embodiments of the invention are not limited to any specific combination of hardware circuitry and software.

[0062] The term “computer-readable medium” as used herein refers to any medium that participates in providing instructions to processor 404 for execution. Such a medium may take many forms, including but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media includes, for example, optical or magnetic disks, such as storage device 410. Volatile media includes dynamic memory, such as main memory 406. Transmission media includes coaxial cables, copper wire and fiber optics, including the wires that comprise bus 402. Transmission media can also take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications.

[0063] Common forms of computer-readable media include, for example, a floppy disk, a flexible disk, hard disk, magnetic tape, or any other magnetic medium, a CD-ROM, any other optical medium, punch cards, paper tape, any other physical medium with patterns of holes, a RAM, a PROM, and EPROM, a FLASH-EPROM, any other memory chip or cartridge, a carrier wave as described hereinafter, or any other medium from which a computer can read.

[0064] Various forms of computer readable media may be involved in carrying one or more sequences of one or more instructions to processor 404 for execution. For example, the instructions may initially be carried on a magnetic disk of a remote computer. The remote computer can load the instructions into its dynamic memory and send the instructions over a telephone line using a modem. A modem local to computer system 400 can receive the data on the telephone line and use an infrared transmitter to convert the data to an infrared signal. An infrared detector coupled to bus 402 can receive the data carried in the infrared signal and place the data on bus 402. Bus 402 carries the data to main memory 406, from which processor 404 retrieves and executes the instructions. The instructions received by main memory 406 may optionally be stored on storage device 410 either before or after execution by processor 404.

[0065] Communication interface 418 also provides a two-way data communication coupling to a network link 420 that is connected to a local network 422. For example, communication interface 418 may be an integrated services digital network (ISDN) card or a modem to provide a data communication connection to a corresponding type of telephone line. As another example, communication interface 418 may be a local area network (LAN) card to provide a data communication connection to a compatible LAN. Wireless links may also be implemented. In any such implementation, communication interface 418 sends and receives electrical, electromagnetic or optical signals that carry digital data streams representing various types of information.

[0066] Network link 420 typically provides data communication through one or more networks to other data devices. For example, network link 420 may provide a connection through local network 422 to a host computer 424 or to data equipment operated by an Internet Service Provider (ISP) 426. ISP 426 in turn provides data communication services through the world wide packet data communication network now commonly referred to as the “Internet” 428. Local network 422 and Internet 428 both use electrical, electromagnetic or optical signals that carry digital data streams. The signals through the various networks and the signals on network link 420 and through communication interface 418, which carry the digital data to and from computer system 400, are exemplary forms of carrier waves transporting the information.

[0067] Computer system 400 can send messages and receive data, including program code, through the network(s), network link 420 and communication interface 418. In the Internet example, a server 430 might transmit a requested code for an application program through Internet 428, ISP 426, local network 422 and communication interface 418. In accordance with the invention, one such downloaded application provides for the techniques and functions that are described herein.

[0068] The received code may be executed by processor 404 as it is received, and/or stored in storage device 410, or other non-volatile storage for later execution. In this manner, computer system 400 may obtain application code in the form of a carrier wave.

[0069] Using the foregoing mechanism, network devices, such as switches and routers, can automatically enable quality of service for the flows in the opposite direction based on the service granted for the original flow for which quality of service was signaled.

[0070] Exemplary applications include video conferencing, other bi-directional video applications, Internet Protocol telephony, and client-server applications in which the links from the clients to the server are also congested and require prioritization. In any of these applications and others, a network administrator may rapidly and easily provide bi-directional quality of service. Devices in the network can be configured to automatically provide quality of service for the opposite direction of a flow so that the network administrator need only classify the traffic from one of the endpoints.

[0071] The techniques disclosed in this document are very useful in a one-to-many configuration, for example, a server with many clients. The packets may be marked on the switch near the servers, and then all switches near the clients are configured to simply mark the opposite flows with the same DiffServ value. Current solutions might require configuring many different ACLs on each and every switch; potentially at least one ACL for each server for quality of service is required.

[0072] Another context is an ISP network, for example, an ISP network that provides virtual private network services, in which a first peer node is within the network and a second peer node is outside the network. The ISP may mark traffic from the first node, for example, by creating and storing an appropriate ACL on the switch or router that is adjacent to the first node. However, for each such node the ISP would have to install a similar ACL on all network devices at the border or edge of the network and going into other ISPs. Further, these ACLs might need to be added and removed dynamically as network flows are created and stopped.

[0073] Advantageously, an embodiment permits the ISP to configure its border routers to mark each flow going through them with the same DSCP on the opposite direction. The network administrator then needs to ensure only that traffic is marked correctly within his network.

[0074] In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative rather than a restrictive sense.