Communication networks can be generally classified into circuit switched networks and packet switched networks. In circuit switched networks, such as telephone networks, when a voice call is set up between two users, the end-to-end communication channel is allocated in a dedicated manner to that voice call. This dedicated availability of communication channel results in a voice call that performs well in terms of relevant quantitative metrics such as intelligibility, delay, and jitter. As a result, the human participants in the voice call perceive the conversation to be qualitatively good and close to an in-person conversation.
In contrast, packet switched networks, such as Internet Protocol (IP) networks, share the available bandwidth between numerous simultaneous traffic flows. A voice call placed over such a network in the form of, say, a Voice over IP (VoIP) call, shares network resources with other concurrent traffic flows. Consequently, the quality of the voice call may vary with the ebb and flow of the concurrent traffic flows that compete for resources. For instance, voice packets may be dropped by a router that is performing at its capacity; or they may incur long delays when they transit through a congested portion of the network; or delays in subsequent voice packets may vary due to the variations in the availability of network resources. There is a need for methods and systems in packet switched networks to ensure that network traffic, such as a VoIP call, is reliably transported over the network.
The concept of Quality of Service (QoS) describes reliable transport of traffic over packet switched networks. Broadly speaking, QoS involves promising and meeting relevant performance metrics for different traffic types. For instance, in the case of voice traffic, QoS may include an upper bound on the latency. Different QoS systems may offer different levels of assurances in meeting this latency upper bound. For instance, a QoS system may only offer its “best effort” under prevailing circumstances, and a different system may group all such voice traffic together and attempt to provision network resources for the voice traffic as a group. Furthermore, different QoS systems may be applicable to different types of networks. Some may only be applicable to packet switched networks that consist of wired links, such as Ethernet and Fiber Optics based Local Area Networks (LAN) or Wide Area Networks (WAN).
A number of systems and methods have been proposed to provide QoS in packet switched networks. These QoS systems are broadly classified into Best Effort, Differentiated Services (DiffServ), and Integrated Services (IntServ) systems.
Best Effort service is one in which no guarantees or promises are provided that a traffic flow will be transported within certain performance metrics, or even that a packet within that traffic flow will be delivered to the destination. The system merely promises best effort under the prevailing circumstances. In DiffServ systems, traffic flows are grouped together into disparate classes, which may be differentiated in their characteristics. For instance, VoIP traffic and video streaming traffic may be assigned to two different classes. DiffServ QoS systems strive to provide network resources across an entire class. Individual flows within a class may not achieve the necessary performance metrics, but the performance metrics are achieved when averaged over the concurrent flows that belong to the same class. In IntServ systems, individual traffic flows are provided for separately from all other traffic flows. For example, the QoS of each VoIP flow is managed and provided for separately. Though this is a promising approach in terms of meeting the specified performance metric for each individual flow, this approach inherently does not scale up to the large number of concurrent traffic flows that occur in a communication network.
Systems and methods have also been proposed to provide QoS for particular packet switched networks. For instance, the Internet Engineering Task Force (IETF) Request for Comments (RFC) 2475, titled “An Architecture for Differentiated Services,” describes a system for providing DiffServ QoS in the Internet. Also, IETF RFC 2205 describes the Resource ReSerVation Protocol (RSVP), which is intended to establish reservations per traffic flow in the Internet and by doing so, provide IntServ QoS in the Internet. Further examples include QoS system and method standards for LAN and WAN networks, such as the Institute of Electrical and Electronics Engineers (IEEE) standards IEEE 802.1p, IEEE 802.1Q and IEEE 802.11e.
These prior art QoS systems and methods have dealt with predominantly wired networks, such as the Internet. Even the work proposed for QoS in wireless communication has largely focused on end-to-end QoS in cellular networks where only the “last hop,” i.e., between the base station and the cellular subscriber, is wireless. For instance, U.S. Pat. No. 6,728,365 B1 extends RSVP signaling to wireless networks for supporting end-to-end QoS in Code Division Multiple Access (CDMA) cellular networks such as CDMA 2000. And, U.S. Pat. No. 6,980,523 B1, in disclosing a system and method for the 3G packet data network, utilizes RSVP to provide end-to-end QoS in a network that is coupled to a wireless mobile station. These QoS systems are applicable to networks that consist predominantly of wired links, with only the link between the base station and cellular subscriber being wireless.
QoS systems have also been proposed for Wireless Local Area Network (WLAN) systems, such as those specified by the IEEE 802.11 standards. For instance, U.S. Pat. No. 7,151,762 B1 introduces virtual streams to support QoS sessions in WLAN. And, US Patent Application Publication No. 2008/0049761 A1 discloses an in-band signaling reference model to support QoS sessions in WLAN. These QoS systems are applicable primarily to WLANs, and do not support networks that are designed with multiple, disparate wireless interfaces.
Communication networks are trending towards convergence, in the sense that users of disparate networks such as the Internet, cellular networks, IEEE 802.11 standards-based WLAN networks, and emerging networks such as Vehicular Area Networks (VANs) can communicate seamlessly with each other. For instance, the user of a VAN should be able to conduct a video conference with one who is connected to the Internet at home, without the quality of the user experience being adversely affected by the mobility of the nodes in the VAN or the differences between the communication capacities of the VAN nodes and the Internet nodes. There is need for a versatile and comprehensive QoS system that can provide the QoS assurances required in such heterogeneous communication scenarios.
The heterogeneous networks can also consist of segments, conventionally described as Mobile Ad Hoc Networks (MANETs), in which the nodes are mobile, wireless, and connected in an ad hoc manner. Providing QoS assurances within such MANET segments as well as when operating in conjunction with other networks, such as cellular networks, is challenging. INSIGNIA, developed by one of the inventors herein, is the first QoS signaling protocol designed to support adaptive QoS guarantees for real-time traffic in MANETs, and is representative of the state of the art in QoS frameworks for mobile MANETs. “INSIGNIA: An IP-Based Quality of Service Framework for Mobile Ad Hoc Networks”, S. B. Lee et al, Journal of Parallel and Distributed Computing, Vol. 60 No. 4 pp. 374-406, April 2000 (Special issue on Wireless and Mobile Computing and Communications). INSIGNIA assumes a flat network in which there is no hierarchy between the nodes. It adopts in-band signaling to piggyback the control information on the IP header of the traffic so that the required node resource reservation and QoS treatment can be provided along the flow, without the need of a pre-established flow path. At each hop, the INSIGNIA packet reserves the bandwidth required to meet the QoS request. INSIGNIA supports fast reservation, fast restoration and responsive adaptation that are specifically designed to deliver adaptive real-time service in MANET.
INSIGNIA, however, is limited in several ways. It is suited to a homogeneous network in which all the nodes have the same interface type. It lacks scalability because all the participating nodes are required to create and maintain resource reservations. As the number of flows in the network increases, some of the INSIGNIA nodes can fail to timely manage the reservations because of the corresponding exponential increases in their number. Also, whenever the network needs to reroute the traffic, requiring topology changes, all the impacted nodes (nodes along the old paths and nodes along the new paths) have to update their reservations. In a highly dynamic network, therefore, the reservations in an INSIGNIA system remain valid for only a short duration, which places a considerable processing burden on the network. INSIGNIA is also only able to support QoS data traffic in the reserved service mode and best effort service mode. There exists a need for a scalable QoS system that has the ability to perform efficient and reliable mobility management over ad hoc connections in order to provide the QoS assurances in heterogeneous communication scenarios that include MANETs.
Communication flows in Internet Protocol (IP)-based networks, such as the Internet and IP-based MANET, may be secured by security protocols, such as Internet Protocol Security (“IPsec”), and security devices, such as the High Assurance Internet Protocol Encryptor (“HAIPE”). Such protocols and devices complicate the provision of QoS assurances because they encrypt the IP datagram to provide the protection. This in turn also encrypts the QoS information described in the IP datagram. In order to provide QoS assurances for secure communication flows protected by such protocols and devices, there is also a need for a QoS system that has the ability to provide QoS assurances in networks to communication flows protected by security protocols such as IPsec and security devices such as HAIPE.