DYNAMIC DIVISION OF ROUTING DOMAINS IN REACTIVE ROUTING NETWORKS
In one embodiment, a reactive routing network may be dynamically divided into reactive routing network sub-domains that comprise a plurality of nodes having bounded route request (RREQ) scopes (e.g., search-domains) that are limited to a particular path length. The transit node in a first reactive routing network sub-domain may receive a RREQ from an originating node within the first reactive routing network sub-domain for a target node determined by the originating node to be beyond the bounded RREQ scope of the originating node. The transit node may then discover a route from the transit node to the target node, and return the route to the originating node. In this manner, the transit node may establish a complete route between the originating node and the target node.
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The present application claims priority to U.S. Provisional Patent Application No. 61/614,703, filed Mar. 23, 2012, entitled TECHNIQUES FOR USE IN REACTIVE ROUTING NETWORKS, by Vasseur, et al., the contents of which are hereby incorporated by reference.
TECHNICAL FIELDThe present disclosure relates generally to communication networks, and, more particularly, to reactive routing in communication networks.
BACKGROUNDLow power and Lossy Networks (LLNs), e.g., sensor networks, have a myriad of applications, such as Smart Grid (smart metering), home and building automation, smart cities, etc. Various challenges are presented with LLNs, such as lossy links, low bandwidth, battery operation, low memory and/or processing capability, etc. Routing in LLNs is undoubtedly one of the most critical challenges and a core component of the overall networking solution. Two fundamentally and radically different approaches, each with certain advantages and drawbacks, have been envisioned for routing in LLN/ad-hoc networks known as:
1) Proactive routing: routing topologies are pre-computed by the control plane (e.g., IS-IS, OSPF, RIP, and RPL are proactive routing protocols); and
2) Reactive routing: routes are computed on-the-fly and on-demand by a node that sends one or more discovery probes throughout the network (e.g., AODV, DYMO, and LOAD are reactive routing protocols).
The embodiments herein may be better understood by referring to the following description in conjunction with the accompanying drawings in which like reference numerals indicate identically or functionally similar elements, of which:
According to one or more embodiments of the disclosure, a reactive routing network may be dynamically divided into reactive routing network sub-domains that comprise a plurality of nodes having bounded route request (RREQ) scopes (e.g., search-domains) that are limited to a particular path length. A transit node may receive a RREQ from an originating node within the first reactive routing network sub-domain for a target node determined by the originating node to be beyond the bounded RREQ scope of the originating node. The transit node may then discover a route from the transit node to the target node, and return the route to the originating node. In this manner, the transit node may establish a complete route between the originating node and the target node.
According to one or more additional embodiments of the disclosure, a node within a reactive routing network may receive a segmentation message from a capable node (e.g., a transit node, a LBR, etc.), and in response, establish a bounded route request (RREQ) scope for any RREQ originated by the node which is limited to a particular path length. As such, the node may forward RREQs to a transit node for any target node not identified by the node as being within the bounded RREQ scope of the node.
DescriptionA computer network is a geographically distributed collection of nodes interconnected by communication links and segments for transporting data between end nodes, such as personal computers and workstations, or other devices, such as sensors, etc. Many types of networks are available, ranging from local area networks (LANs) to wide area networks (WANs). LANs typically connect the nodes over dedicated private communications links located in the same general physical location, such as a building or campus. WANs, on the other hand, typically connect geographically dispersed nodes over long-distance communications links, such as common carrier telephone lines, optical lightpaths, synchronous optical networks (SONET), synchronous digital hierarchy (SDH) links, or Powerline Communications (PLC) such as IEEE 61334, IEEE 21901.2, and others. In addition, a Mobile Ad-Hoc Network (MANET) is a kind of wireless ad-hoc network, which is generally considered a self-configuring network of mobile routes (and associated hosts) connected by wireless links, the union of which forms an arbitrary topology.
Smart object networks, such as sensor networks, in particular, are a specific type of network having spatially distributed autonomous devices such as sensors, actuators, etc., that cooperatively monitor physical or environmental conditions at different locations, such as, e.g., energy/power consumption, resource consumption (e.g., water/gas/etc. for advanced metering infrastructure or “AMI” applications) temperature, pressure, vibration, sound, radiation, motion, pollutants, etc. Other types of smart objects include actuators, which may be, e.g., responsible for turning on/off an engine or perform any other actions. Sensor networks, a type of smart object network, are typically shared-media networks, such as wireless or PLC networks. That is, in addition to one or more sensors, each sensor device (node) in a sensor network may generally be equipped with a radio transceiver or other communication port such as PLC, a microcontroller, and an energy source, such as a battery. Often, smart object networks are considered field area networks (FANs), neighborhood area networks (NANs), etc. Generally, size and cost constraints on smart object nodes (e.g., sensors) result in corresponding constraints on resources such as energy, memory, computational speed and bandwidth. Correspondingly, a reactive routing protocol may, though need not, be used in place of a proactive routing protocol for smart object networks.
Data packets 140 (e.g., traffic and/or messages sent between the devices/nodes) may be exchanged among the nodes/devices of the computer network 100 using predefined network communication protocols such as certain known wired protocols, wireless protocols (e.g., IEEE Std. 802.15.4, WiFi, Bluetooth®, etc.), PLC protocols, or other shared-media protocols where appropriate. In this context, a protocol consists of a set of rules defining how the nodes interact with each other.
The network interface(s) 210 contain the mechanical, electrical, and signaling circuitry for communicating data over links 105 coupled to the network 100. The network interfaces may be configured to transmit and/or receive data using a variety of different communication protocols. Note, further, that the nodes may have two different types of network connections 210, e.g., wireless and wired/physical connections, and that the view herein is merely for illustration. Also, while the network interface 210 is shown separately from power supply 260, for PLC the network interface 210 may communicate through the power supply 260, or may be an integral component of the power supply. In some specific configurations the PLC signal may be coupled to the power line feeding into the power supply.
The memory 240 comprises a plurality of storage locations that are addressable by the processor 220 and the network interfaces 210 for storing software programs and data structures associated with the embodiments described herein. Note that certain devices may have limited memory or no memory (e.g., no memory for storage other than for programs/processes operating on the device and associated caches). The processor 220 may comprise hardware elements or hardware logic adapted to execute the software programs and manipulate the data structures 245. An operating system 242, portions of which are typically resident in memory 240 and executed by the processor, functionally organizes the device by, inter alia, invoking operations in support of software processes and/or services executing on the device. These software processes and/or services may comprise an illustrative routing process 244, as described herein. Note that while the routing process 244 is shown in centralized memory 240, alternative embodiments provide for the process to be specifically operated within the network interfaces 210.
It will be apparent to those skilled in the art that other processor and memory types, including various computer-readable media, may be used to store and execute program instructions pertaining to the techniques described herein. Also, while the description illustrates various processes, it is expressly contemplated that various processes may be embodied as modules configured to operate in accordance with the techniques herein (e.g., according to the functionality of a similar process). Further, while the processes have been shown separately, those skilled in the art will appreciate that processes may be routines or modules within other processes.
Routing process (services) 244 contains computer executable instructions executed by the processor 220 to perform functions provided by one or more routing protocols, such as proactive or reactive routing protocols as will be understood by those skilled in the art. These functions may, on capable devices, be configured to manage a routing/forwarding table (a data structure 245) containing, e.g., data used to make routing/forwarding decisions. In particular, in proactive routing, connectivity is discovered and known prior to computing routes to any destination in the network, e.g., link state routing such as Open Shortest Path First (OSPF), or Intermediate-System-to-Intermediate-System (ISIS), or Optimized Link State Routing (OLSR). Reactive routing, on the other hand, discovers neighbors (i.e., does not have an a priori knowledge of network topology), and in response to a needed route to a destination, sends a route request into the network to determine which neighboring node may be used to reach the desired destination. Example reactive routing protocols may comprise Ad-hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR), DYnamic MANET On-demand Routing (DYMO), LLN On-demand Ad hoc Distance-vector (LOAD), etc. Notably, on devices not capable or configured to store routing entries, routing process 244 may consist solely of providing mechanisms necessary for source routing techniques. That is, for source routing, other devices in the network can tell the less capable devices exactly where to send the packets, and the less capable devices simply forward the packets as directed.
Notably, mesh networks have become increasingly popular and practical in recent years. In particular, shared-media mesh networks, such as wireless or PLC networks, etc., are often on what is referred to as Low-Power and Lossy Networks (LLNs), which are a class of networks in which both the routers and their interconnect are constrained: LLN routers typically operate with constraints, e.g., processing power, memory, and/or energy (battery), and their interconnects are characterized by, illustratively, high loss rates, low data rates, and/or instability. LLNs are comprised of anything from a few dozen and up to thousands or even millions of LLN routers, and support point-to-point traffic (between devices inside the LLN), point-to-multipoint traffic (from a central control point such at the root node to a subset of devices inside the LLN) and multipoint-to-point traffic (from devices inside the LLN towards a central control point).
An example implementation of LLNs is an “Internet of Things” network. Loosely, the term “Internet of Things” or “IoT” may be used by those in the art to refer to uniquely identifiable objects (things) and their virtual representations in a network-based architecture. In particular, the next frontier in the evolution of the Internet is the ability to connect more than just computers and communications devices, but rather the ability to connect “objects” in general, such as lights, appliances, vehicles, HVAC (heating, ventilating, and air-conditioning), windows and window shades and blinds, doors, locks, etc. The “Internet of Things” thus generally refers to the interconnection of objects (e.g., smart objects), such as sensors and actuators, over a computer network (e.g., IP), which may be the Public Internet or a private network. Such devices have been used in the industry for decades, usually in the form of non-IP or proprietary protocols that are connected to IP networks by way of protocol translation gateways. With the emergence of a myriad of applications, such as the smart grid, smart cities, and building and industrial automation, and cars (e.g., that can interconnect millions of objects for sensing things like power quality, tire pressure, and temperature and that can actuate engines and lights), it has been of the utmost importance to extend the IP protocol suite for these networks.
As noted above, routing in LLNs is undoubtedly one of the most critical challenges and a core component of the overall networking solution. Two fundamentally and radically different approaches have been envisioned for routing in LLN/ad-hoc networks known as proactive routing (routing topologies are pre-computed by the control plane) and reactive routing (routes are computed on-the-fly and on-demand by a node that sends a discovery probes throughout the network).
An example proactive routing protocol specified in an Internet Engineering Task Force (IETF) Proposed Standard, Request for Comment (RFC) 6550, entitled “RPL: IPv6 Routing Protocol for Low Power and Lossy Networks” by Winter, et al. (March 2012), provides a mechanism that supports multipoint-to-point (MP2P) traffic from devices inside the LLN towards a central control point (e.g., LLN Border Routers (LBRs) or “root nodes/devices” generally), as well as point-to-multipoint (P2MP) traffic from the central control point to the devices inside the LLN (and also point-to-point, or “P2P” traffic). RPL may generally be described as a distance vector routing protocol that builds a Directed Acyclic Graph (DAG) or Destination Oriented Directed Acyclic Graphs (DODAGs) for use in routing traffic/packets 140 from a root using mechanisms that support both local and global repair, in addition to defining a set of features to bound the control traffic, support repair, etc. One or more RPL instances may be built using a combination of metrics and constraints.
An example reactive routing protocol is specified in an IETF Internet Draft, entitled “LLN On-demand Ad hoc Distance-vector Routing Protocol-Next Generation (LOADng)” <draft-clausen-lln-loadng-05> by Clausen, et al. (Jul. 14, 2012 version), which provides a reactive routing protocol for LLNs, e.g., as derived from AODV. Other reactive routing protocol efforts include the G3-PLC specification approved by the ITU, and also one described in an informative annex of IEEE P1901.2.
One stated benefit of reactive routing protocols is that their state and communication overhead scales with the number of active sources and destinations in the network. Such protocols only initiate control traffic and establish state when a route to a destination is unknown. In contrast, proactive routing protocols build and maintain routes to all destinations before data packets arrive and incur state and communication overhead that scales with the number of nodes, rather than the number of active sources and destinations. Some believe that reactive routing protocols are well-suited for certain Smart Grid Automated Meter Reading (AMR) applications where a Collection Engine reads each meter one-by-one in round-robin fashion. In such simplistic applications, only one source-destination pair is required at any point in time.
Reactive routing protocols, however, have a number of technical issues that are particularly exhibited in large-scale LLNs, such as large utility networks. It is thus important to have a robust solution for reactive routing. Therefore, various techniques are hereinafter shown and described for use with reactive routing networks to address such shortcomings.
Dynamic Division of Reactive Routing Networks into Sub-Domains
Reactive routing protocols rely on flooding the whole network with probes/messages (e.g., RREQs) to discover routes between a source and a destination within the network. Unfortunately, such network floods generate significant volumes of network traffic. Several mitigation techniques have been developed to reduce the negative effects of flooding by reducing/limiting the number of broadcast packets generated by such floods. Illustratively, these techniques may operate by attempting to limit the flood scope, the number of duplicated messages (e.g., multicast trickle), etc. Nevertheless, such network floods are still generally required for any reactive routing protocol in order to make sure that at least N probes/messages reach the destination/target. It is important to note that while N may be small in “classic” networks that have high delivery rates, N is likely to be higher in LLNs in which the Packet Delivery Ratio (PDR) is typically low. Unfortunately, these mitigation techniques lead to a trade-off between storing network state and increasing network load due to flooded messages (e.g., a RREQ broadcast). For example, storing more network state information makes it possible to reduce the number of times that the discovery process (e.g., a network flood) must be triggered, and therefore decreases the control plane overhead; however, storing more state information requires more memory to store the routing entries for each originator, especially in cases where the routes are not limited to the best next hops, but rather include full end-to-end paths from the source to the destination, which increases cost.
The techniques herein provide dynamic division of a reactive routing network into sub-domains by allowing a routing sub-domain to be dynamically divided into search-domains based on the observed message flood rate within the network, thus significantly reducing the message flood rate in the network, as well as the associated control plane cost.
Specifically, according to one or more embodiments of the disclosure as described in detail below, a reactive routing network may be dynamically divided into reactive routing network sub-domains that each include nodes with bounded route request (RREQ) scopes (e.g., search-domains) that are limited to a particular path length. In other words, a reactive routing network sub-domain includes a plurality of nodes, each of which has a search-domain with a limited number of surrounding nodes that may receive a RREQ from that particular node. A transit node may receive a RREQ from an originating node within a first reactive routing network sub-domain for a target node determined by the originating node to be beyond the bounded RREQ scope (i.e., search-domain) of the originating node. The transit node may then discover a route from the transit node to the target node, and return the route to the originating node. The discovered route may include at least one node in a second reactive routing network sub-domain, which is outside of the first reactive routing network sub-domain. In this manner, the transit node may establish a complete route between the originating node and the target node. In addition, according to one or more additional embodiments of the disclosure, a node within a reactive routing network may receive a segmentation message from a capable node (e.g., a transit node, a LBR, etc.), and in response, establish a bounded RREQ scope (e.g., a search-domain) for any RREQ originated by the node that is limited to a particular path length. As such, the node may forward RREQs to one or more transit nodes for any target node not identified by the node as being within the search-domain of the node.
Illustratively, the techniques described herein may be performed by hardware, software, and/or firmware, such as in accordance with the routing process 244, which may contain computer executable instructions executed by the processor 220 (or independent processor of interfaces 210) to perform functions relating to the novel techniques described herein. For example, the techniques herein may be treated as extensions to conventional routing protocols, such as the various reactive routing protocols, and as such, may be processed by similar components understood in the art that execute those protocols, accordingly.
The techniques herein may dynamically divide a reactive routing network into reactive routing sub-domains based on observed message flood patterns within the network and/or based on network conditions (e.g., link/node congestion state). Advantageously, the reactive routing sub-domains of the disclosure may restrict flooding scope within the network as a whole by, for example, establishing a search-domain for each node within the reactive routing sub-domain that comprises a limited number of surrounding nodes that may receive a RREQ from that particular node. In the event that a node within a reactive routing sub-domain (e.g., an originating node) initiates a RREQ within its search-domain and is unable to identify a path to a desired target node, the originating node may then attempt to identify the target node with the aide of a transit node. For example, unicast or loose source routing may be used to reach out (or out-of-search-domain) target destinations via dynamically discovered points of transit (e.g., transit nodes), with a resulting decrease in control plane cost overhead. Additionally, capable nodes within the reactive routing network may serve to establish search-domain boundaries within the network, which may be based on control plane cost overhead due to flooded messages (e.g., network state) within the reactive routing network prior to reactive routing network division into reactive routing sub-domains.
According to the techniques herein, route discovery in a reactive routing network may be facilitated by the use of transit nodes. For example,
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- 1) Node 43 may return all of the received messages/probes to node 13 with the recorded path (e.g., a route reply or “RREP”), and path selection may be performed by node 13 on the basis of the path cost, as indicated by the received messages/probes;
- 2) Node 43 may arm a timer upon receiving the first message/probe from node 13, and once the timer has expired, node 43 may select the received message/probe with the “best” path according to the path cost; and/or
- 3) Node 43 may immediately return the first received message/probe to node 13 in order to avoid wasting time before sending the data packet, and may store the path cost for that particular message/probe and only return further messages/probes if their path cost is better then the path cost for the original message/probe by a particular value “X” (e.g., by X %).
Illustratively, once a route is discovered between node 13 (e.g., source/requestor) and node 43 (e.g., destination), for example 13-12-22-32-43 as shown in
Operationally, the techniques herein may provide a software module referred to as a Distributed Intelligent Agent-Broadcast (DIA B), which may be hosted by a capable node/device (e.g., the LBR) within the reactive routing network or on a separate device, such as a network management server (NMS) or other management device. For example, the DIA-B may be encompassed by routing process 244 (see, e.g.,
In addition, the techniques herein provide that all DIA-B processes, or other capable nodes/devices, may announce themselves as potential transit nodes. For example, DIA-B processes may self-identify as potential transit nodes via an IPv6 broadcast message(s), or via a routing protocol that may advertise their node capability such as, for example, a routing metric specified in IETF Internet Draft, entitled “Routing Metrics used for Path Calculation in Low Power and Lossy Networks” <draft-ietf-roll-routing-metrics-19> by Vasseur, et al. (Mar. 1, 2011 version) for the RPL protocol, or IS-IS node capability extensions in the event that ISIS may be used by the LBR on the core network backbone.
Operationally, the techniques herein provide a control plane overhead threshold value that may determine when routing region division should occur within the reactive routing network. For example, if the DIA-B process determines that the control plane overhead due to flooded messages/probes (e.g., RREQs) does not exceed the pre-defined threshold value, or that there are no congested areas in the network that would benefit from a reduction of the number of flooded messages/probes, then the DIA-B process may determine that no action is required with respect to routing region division. However, if the DIA-B process determines that the control plane overhead due to flooded messages/probes does exceed the pre-defined threshold value, then the DIA-B process may trigger dynamic division of the reactive routing network into one or more routing sub-domains via the following exemplary set of actions.
A capable node/device (e.g., an LBR, a NMS, a transit node, etc.) may perform a scoped flood of a new message, referred to herein as the Segmentation Message (e.g., an IPv6 message), for all destinations within a specific distance such that all nodes receiving the Segmentation Message comprise a reactive routing sub-domain. The Segmentation Message may cause nodes receiving the message to bound the scope of any subsequent route discovery messages (e.g., RREQs) flooded by such receiving nodes, e.g., by setting the TTL value of the flooded route discovery messages to specified path length “PL(i)”, as described below, which may create search-domains for each node within the reactive routing sub-domain. In this manner, the Segmentation Message may create a threshold at which the receiving node (e.g., a source node) may transition from a flooding protocol to a transit node transmission protocol when discovering routes within the network. For example, the Segmentation Message may establish a threshold level at which a source node may transition from a protocol of flooding a RREQ within the bounded scope of surrounding nodes/devices set by the Segmentation Message (i.e., a search-domain), to a protocol of transmitting messages directly to a transit node (e.g., the transit node that originated the Segmentation Message, or another transit node), which may then continue the search to complete the route request (if the transit node is not already aware of the intended target node of the route request).
Illustratively, direct transmission from the source node to the transit node may occur by unicasting or by “loose-hop” routing with the transit node set as the first next loose hop. In other words, a capable node may transmit a Segmentation Message to a subset of nodes/devices within a reactive routing network via a scoped flood (e.g., a sub-domain), and the Segmentation Message may then direct the subset of nodes/devices (i.e., the routing sub-domain) to use flooding to identify any target node ≦“X” hops away (e.g., PL(i)), which creates a search-domain, and if no RREP is received within “N” attempts, to then transmit that corresponding RREQ directly to a transit node via unicast or loose hop routing so that the transit node may continue the search for the target node.
Note that in one embodiment, the Segmentation Message may be unicast to any capable node (e.g., a LBR, a transit node, a NMS, etc.), which may then flood the Segmentation Message with a time-to-live (TTL) indicator (i.e., a scoped flood of the Segmentation Message). Advantageously, this approach may allow the capable node (e.g., the LBR/root or transit node) to divide the network into one or more routing sub-domains by delivering the Segmentation Message to a localized region of the network. In another embodiment, the Segmentation Message may be broadcast to all nodes in the network (e.g., from a central network management device), and may affect how all nodes in the network operate. In still another embodiment, the Segmentation Message may be unicast to individual nodes within the reactive routing network. It is contemplated within the scope of the disclosure that a routing sub-domain may, or may not, contain a transit node.
Illustratively,
Upon receiving the SM 300, each node within the network may begin bounding the scope of any flooded message/probe (RREQ) by setting the TTL value of the packet to PL(i), effectively creating search-domains within the routing sub-domain. For example, if PL=3, then node 21 in the expanded network would not be able to find a direct route to node 25 using RREQ messages because it exceeds the hop threshold. Instead, a route from node 21 to note 25 may be established using the mechanism described below.
If a destination node cannot be reached within the source node's search-domain (e.g., no RREP packet has been received after “N” trials, where N≧1), then the source node may begin to use loose routing, with LBR1 set as the first next loose hop, essentially, to let the transit node complete the unknown path to the destination/target node. If the route to the LBR1 is known, then the source node may source route the packet with the last two entries listed as loose hops. For example, if the packet received by node 42 seeks a path to node 25, the packet may carry the following source route: 42-32-22-12-LBR1(L)-25(L) (where “(L)” indicates the ends of a loose hop). If the source node does not know the source route to the closest transit node, it may either send a message/probe to discover a path to the node or, if available, it may use a simple proactive DAG to provide hop-by-hop upward routing to the LBR of interest. Upon receiving such a loose route message/probe, LBR1 may then add the next hop entry (e.g., LBR2) in any of a variety of ways. For example, LBR1 may multicast the RREQ to other transit nodes within the reactive routing network to determine whether any may be able to complete the route to the target node. If none of the queried transit nodes are able to complete the route (e.g., if the target node is not located within a transit node associated network sub-domain), LBR1 may then flood the RREQ to the entire network to identify a route to the target node.
In the event that the target node is located within the LBR2 network sub-domain, and LBR2 knows the path to the target node, then LBR2 may return the completed route to LBR1. However, if LBR2 does not know the route to the target node, it may then initiate a local message/probe broadcast with the destination target node desired by the source node with, for example, a TTL value of PL(2) (i.e., the value of the Path Length in its own search-domain). Upon receiving the reply (e.g., a RREP) from the destination node, the discovered path may be added to the RREP messages and sent back to the requesting LBR, which may, in turn, return the RREP to the source node with the fully discovered path 310, for example, 42-32-22-12-LBR1-LBR2-14-25, as shown in
In addition, the LBRs may keep track of the number of identified loose routes so as to dynamically adjust the values of PL(i). Larger values of PL(i) may lead to wider search-domains and more optimal paths at the cost of increased broadcast domains.
Notably, the value of PL(i) may have a number of consequences, and may be chosen by the initiating LBR according to the presence of other LBRs to make sure that PL(i) (i being the search-domain) may be chosen so as to guarantee existence of a path between each pair of nodes in the network. For example, as described above, if LBR2 sets the TTL value as PL(1)=4, then node 42 would not be able to establish a route to node 14. In order to compensate for this scenario, LBR2 may set the value of PL(2) high enough to guarantee that a path will be found.
In view of the foregoing, one of skill in the art will appreciate that
It is contemplated within the scope of the disclosure that reactive routing network sub-domains may, or may not, overlap. As shown in
In addition, as described above, the techniques herein provide that a source node within a particular routing sub-domain may route a RREQ to one or more different transit node(s). For example,
In addition, the techniques herein also provide that TN1 may directly query specific “linked” transit nodes within the dynamically divided reactive routing network in order to complete route discovery. For example, as shown in
The techniques herein provide a significant increase in efficiency and decrease in control plane overhead because the bounded RREQ scope search-domains and the ability of transit nodes to efficiently complete route discover may significantly decrease overall network traffic. In addition, even if it is necessary for a particular transit node (e.g., LBR1/TN1) to initiate a network flood to identify a route to a target node, the techniques herein may allow that discovered route to remain available for other nodes within the LBR1 sub-domain looking to reach the same target node, which may prevent additional network floods.
Similarly,
It should be noted that while certain steps within procedures 400 and 500 may be optional as described above, the steps shown in
The techniques described herein, therefore, provide for dynamic division of reactive routing networks into reactive routing sub-domains in order to control/minimize flooding, which provides increased scalability for reactive routing networks. By using the transit nodes as a bridge to help reach the final destination node, the techniques herein may reduce congestion in reactive routing networks. In particular, the techniques herein increase scalability both for an increase in the number of nodes in a network, and for small networks as the number of active P2P flows in the network increases.
While there have been shown and described illustrative embodiments of techniques for use with reactive routing in communication networks, it is to be understood that various other adaptations and modifications may be made within the spirit and scope of the embodiments herein. For example, the embodiments have been shown and described herein with relation to LLNs. However, the embodiments in their broader sense are not as limited, and may, in fact, be used with other types of networks, regardless of whether they are considered constrained. In addition, while certain protocols are shown, other suitable protocols may be used, accordingly.
The foregoing description has been directed to specific embodiments. It will be apparent, however, that other variations and modifications may be made to the described embodiments, with the attainment of some or all of their advantages. For instance, it is expressly contemplated that the components and/or elements described herein can be implemented as software being stored on a tangible (non-transitory) computer-readable medium (e.g., disks/CDs/RAM/EEPROM/etc.) having program instructions executing on a computer, hardware, firmware, or a combination thereof Accordingly this description is to be taken only by way of example and not to otherwise limit the scope of the embodiments herein. Therefore, it is the object of the appended claims to cover all such variations and modifications as come within the true spirit and scope of the embodiments herein.
Claims
1. A method, comprising:
- receiving, at a transit node, a route request (RREQ) for a target node from an originating node within a first reactive routing network sub-domain, wherein the first reactive routing network sub-domain comprises a plurality of nodes having a bounded RREQ scope limited to a particular path length, and the target node is beyond the bounded RREQ scope of the originating node;
- discovering a route from the transit node to the target node; and
- returning the route to the originating node to establish a complete route between the originating node and the target node.
2. The method as in claim 1, wherein the bounded RREQ scope is set by a segmentation message broadcast to the originating node.
3. The method as in claim 2, wherein the segmentation message comprises a time-to-live indicator to be used in RREQs broadcast by the plurality of nodes within the first reactive routing network sub-domain.
4. The method as in claim 2, further comprising:
- triggering broadcast of the segmentation message in response to control plane overhead of the reactive routing network exceeding a predetermined threshold value.
5. The method as in claim 2, wherein the segmentation message comprises a time-to-live indicator which limits the plurality of nodes contacted by the segmentation message and define a boundary for the first reactive routing network sub-domain.
6. The method as in claim 1, wherein the RREQ for the target node comprises the transit node as a first loose hop and the target node as a final loose hop.
7. The method as in claim 4, wherein the segmentation message is broadcast in response to an instruction from a management device.
8. The method as in claim 1, wherein discovering further comprises:
- multicasting the RREQ to one or more transit nodes in a reactive routing network.
9. The method as in claim 1, wherein discovering further comprises:
- broadcasting the RREQ to a reactive routing network.
10. The method as in claim 1, wherein discovering further comprises:
- identifying a route to the target node based on a route reply (RREP) received from a previous RREQ sent prior to the receiving step.
11. The method as in claim 1, wherein the transit node is a border router for the first reactive routing network sub-domain,
12. A method, comprising:
- receiving, at a node within a reactive routing network, a segmentation message;
- establishing, in response to the segmentation message, a bounded route request (RREQ) scope for any RREQ originated by the node to cause each RREQ to be limited to a particular path length; and
- forwarding at least one RREQ to a transit node for any target node not identified by the node as being within the bounded RREQ scope of the node.
13. The method as in claim 12, wherein the segmentation message comprises a time-to-live indicator to be used in RREQs broadcast by a plurality of nodes within a first reactive routing network sub-domain.
14. The method as in claim 12, wherein the segmentation message is received from the transit node.
15. The method as in claim 12, wherein the node, having determined that the target node is not within the bounded RREQ scope, uses a proactive directed acyclic graph (DAG) to provide a route to the transit node, or broadcasts a RREQ to identify a route to the transit node.
16. The method as in claim 12, wherein forwarding further comprises:
- setting the RREQ to indicate the transit node as the first loose hop and the target node as the final loose hop.
17. The method as in claim 12, further comprising:
- receiving a route reply (RREP) from the transit node, the RREP indicating an entire path from the originating node to the target node via the transit node.
18. The method as in claim 12, further comprising:
- receiving segmentation messages from two or more transit nodes; and
- picking one particular transit node to receive forwarded RREQs.
19. An apparatus, comprising:
- one or more network interfaces to communicate within a computer network;
- a processor coupled to the network interfaces and adapted to execute one or more processes; and
- a memory configured to store a process executable by the processor, the process when executed operable to: receive, as a transit node, a route request (RREQ) for a target node from an originating node within a first reactive routing network sub-domain, wherein the first reactive routing network sub-domain comprises a plurality of nodes having a bounded RREQ scope limited to a particular path length, and the target node is beyond the bounded RREQ scope of the originating node; discover a route from the transit node to the target node; and return the route to the originating node to establish a complete route between the originating node and the target node.
20. The apparatus as in claim 19, wherein the process is configured to broadcast a segmentation message indicating the bounded RREQ scope.
21. The apparatus as in claim 20, the segmentation message comprising a time-to-live indicator to be used in RREQs broadcast by the plurality of nodes within the first reactive routing network sub-domain.
22. The apparatus as in claim 20, the segmentation message comprising a time-to-live indicator to limit the plurality of nodes contacted by the segmentation message and define a boundary for the first reactive routing network sub-domain.
23. The apparatus as in claim 19, wherein the process when executed is further operable to:
- trigger broadcast of the segmentation message in response to control plane overhead of the reactive routing network exceeding a predetermined threshold value.
24. An apparatus, comprising:
- one or more network interfaces to communicate within a computer network;
- a processor coupled to the network interfaces and adapted to execute one or more processes; and
- a memory configured to store a process executable by the processor, the process when executed operable to: receive, as a node within a reactive routing network, a segmentation message; establish, in response to the segmentation message, a bounded route request (RREQ) scope for any RREQ originated by the node which is limited to a particular path length; and forward RREQs to a transit node for any target node not identified by the node as being within the bounded RREQ scope of the node.
25. The apparatus as in claim 24, wherein the segmentation message comprises a time-to-live indicator to be used in RREQs broadcast by a plurality of nodes within a first a reactive routing network sub-domain
Type: Application
Filed: Sep 6, 2012
Publication Date: Sep 26, 2013
Applicant: Cisco Technology, Inc. (San Jose, CA)
Inventors: Jean-Philippe Vasseur (Saint Martin d'Uriage), Jonathan W. Hui (Belmont, CA)
Application Number: 13/605,528
International Classification: H04L 12/28 (20060101);