The present disclosure generally relates to network routing protocol technologies. More particularly, and not by way of any limitation, the present disclosure is directed to a method and apparatus for protocol data unit synchronization in an Intermediate System-Intermediate System (IS-IS) router operable in an IS-IS routing network.
An IS-IS router referred to herein has, among its many functionalities, an ability to generate link state protocol data units (LSPs) to describe the routers and links to which it is connected. The information regarding the connected routers and links may be received from other modules in the router, such as physical ports.
Typically, a standby router module and an active router module may be provided as part of the IS-IS router in order to facilitate the capability referred to as Non Stop Routing (NSR). To support NSR capability, databases used for routing must be synchronized between the standby and active router modules so that when the standby router module becomes active, it has a complete database to function seamlessly.
Embodiments of the present disclosure are illustrated by way of example, and not by way of limitation, in the Figures of the accompanying drawings in which like references indicate similar elements. It should be noted that different references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references may mean at least one. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to effect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.
The accompanying drawings are incorporated into and form a part of the specification to illustrate one or more exemplary embodiments of the present disclosure. Various advantages and features of the disclosure will be understood from the following Detailed Description taken in connection with the appended claims and with reference to the attached drawing Figures in which:
The present patent disclosure is broadly directed to a method and apparatus for synchronizing LSPs in an IS-IS router having redundancy for purposes of effectuating Non Stop Routing. The present patent disclosure is also directed to associated computer-accessible media, computer programmable products and various software/firmware components relative to the LSP synchronization techniques set forth herein.
In one aspect, an embodiment of a method of synchronizing LSPs in a network element operating as an IS-IS router is disclosed, wherein the IS-IS router may comprise an active route processor (RP) module and a standby route processor (RP) module. The claimed embodiment comprises, inter alia, receiving one or more remote LSP updates from at least one adjacent IS-IS router by an active IS-IS process associated with the active RP module and updating a first remote LSP database portion of a first link state database associated with the active IS-IS process, the updating being effectuated using raw LSPs corresponding to the received one or more remote LSP updates. The claimed method may also include updating a first local LSP database portion of the first link state database based on one or more local LSP updates generated by the active IS-IS process and sending the updated local LSPs to the neighboring routers. A first synchronization process of the claimed method involves synchronizing of the one or more remote LSP updates between the first remote LSP database portion of the first link state database and a second remote LSP database portion of a second link state database associated with a standby IS-IS process on the standby RP module, the first synchronizing being effectuated using raw LSPs corresponding to the one or more remote LSP updates received by the active IS-IS process. A second synchronization process of the claimed method involves synchronizing of the one or more local LSP updates between the first local LSP database portion of the first link state database and a second local LSP database portion of the second link state database associated with the standby IS-IS process, the second synchronizing being effectuated using raw LSPs corresponding to the one or more local LSP updates generated by the active IS-IS process. In another aspect, an embodiment of a non-transitory computer-readable medium containing instructions stored thereon is disclosed. When the stored instructions are executed by a computer system configured to operate as an IS-IS router, the computer system is operable to perform an embodiment of the method set forth above.
In a still further aspect, an embodiment of a network element configured to operate as an IS-IS router is disclosed. The claimed embodiment comprises, inter alia, an active RP module supporting an active IS-IS routing process based on a first link state database, the first link state database including a first local LSP database portion and a first remote LSP database portion, and a standby route processor (RP) module supporting a standby IS-IS process associated with a second link state database, wherein the second link state database includes a second local LSP database portion and a second remote LSP database portion. The claimed network element also includes an inter-process communication module configured to facilitate a first synchronization of one or more remote LSP updates received by the active IS-IS process between the first remote LSP database portion of the first link state database and the second remote LSP database portion of the second link state database, the first synchronization being effectuated using raw LSPs corresponding to the one or more remote LSP updates received by the active IS-IS process, and a second synchronization of one or more local LSP updates generated by the active IS-IS process between the first local LSP database portion of the first link state database and the second local LSP database portion of the second link state database, the second synchronization being effectuated using raw LSPs corresponding to the one or more local LSP updates generated by the active IS-IS process.
In the following description, numerous specific details are set forth with respect to one or more embodiments of the present patent disclosure. However, it should be understood that one or more embodiments may be practiced without such specific details. In other instances, well-known circuits, subsystems, components, structures and techniques have not been shown in detail in order not to obscure the understanding of the example embodiments. Accordingly, it will be appreciated by one skilled in the art that the embodiments of the present disclosure may be practiced without such specific details. It should be further recognized that those of ordinary skill in the art, with the aid of the Detailed Description set forth herein and taking reference to the accompanying drawings, will be able to make and use one or more embodiments without undue experimentation.
Additionally, terms such as “coupled” and “connected,” along with their derivatives, may be used in the following description, claims, or both. It should be understood that these terms are not necessarily intended as synonyms for each other. “Coupled” may be used to indicate that two or more elements, which may or may not be in direct physical or electrical contact with each other, co-operate or interact with each other. “Connected” may be used to indicate the establishment of communication, i.e., a communicative relationship, between two or more elements that are coupled with each other. Further, in one or more example embodiments set forth herein, generally speaking, an element, component or module may be configured to perform a function if the element is capable of performing or otherwise structurally arranged to perform that function.
As used herein, a network element (e.g., a router, switch, bridge, etc.) is a piece of networking equipment, including hardware and software that communicatively interconnects other equipment on a network (e.g., other network elements, end stations, etc.). Some network elements may comprise “multiple services network elements” that provide support for multiple networking functions (e.g., routing, bridging, switching, Layer-2 aggregation, session border control, Quality of Service, and/or subscriber management, and the like), and/or provide support for multiple application services (e.g., data, voice, and video). Subscriber end stations (e.g., servers, workstations, laptops, netbooks, palm tops, mobile phones, smartphones, multimedia phones, Voice Over Internet Protocol (VOIP) phones, user equipment, terminals, portable media players, GPS units, gaming systems, set-top boxes) may access or consume content/services provided over a packet-switched wide area public network such as the Internet via suitable service provider access networks. Subscriber end stations may also access or consume content/services provided on virtual private networks (VPNs) overlaid on (e.g., tunneled through) the Internet. It should be appreciated that one or more embodiments of the present patent disclosure involving IS-IS routing protocol functionality may be implemented in such arrangements wherein the content and/or services are typically provided by one or more end stations (e.g., server end stations) belonging to a service or content provider. Alternatively or additionally, content and/or services may be consumed among the end stations participating in a peer-to-peer service, and may include, for example, public webpages (e.g., free content, online store fronts, search services, etc.), private webpages (e.g., username/password accessed webpages providing email services), and/or corporate networks over VPNs. Typically, subscriber end stations may be coupled (e.g., through customer premise equipment or CPE coupled to an access network (wired or wirelessly)) to edge network elements, which are coupled (e.g., through one or more core network elements) to other edge network elements, which are coupled to other end stations (e.g., server end stations).
One or more embodiments of the present patent disclosure may be implemented using different combinations of software, firmware, and/or hardware. Thus, one or more of the techniques shown in the Figures (e.g., flowcharts) may be implemented using code and data stored and executed on one or more electronic devices (e.g., an end station, a network element, etc.). Such electronic devices may store and communicate (internally and/or with other electronic devices over a network) code and data using computer-readable media, such as non-transitory computer-readable storage media (e.g., magnetic disks, optical disks, random access memory, read-only memory, flash memory devices, phase-change memory, etc.), transitory computer-readable transmission media (e.g., electrical, optical, acoustical or other form of propagated signals—such as carrier waves, infrared signals, digital signals), etc. In addition, such electronic devices may typically include a set of one or more processors coupled to one or more other components, such as one or more storage devices (non-transitory machine-readable storage media), user input/output devices (e.g., a keyboard, a touch screen, a pointing device, and/or a display), and network connections. The coupling of the set of processors and other components may be typically through one or more buses and bridges (also termed as bus controllers), arranged in any known (e.g., symmetric/shared multiprocessing) or heretofore unknown architectures. Thus, the storage device or component of a given electronic device may be configured to store code and/or data for execution on one or more processors of that electronic device for purposes of implementing one or more techniques of the present disclosure.
By way of example, embodiments of the present patent disclosure will be described below in detail by taking reference to a router network based on the Intermediate System-to-Intermediate System (IS-IS) routing protocol. IS-IS routing protocol, which is standardized according to the ISO/IEC 10589 specification, incorporated by reference herein, is a link-state protocol similar to Open Shortest Path First (OSPF) routing protocol. As is known, a link-state routing protocol is one of the two main classes of routing protocols used in packet-switching networks for communications, the other being the distance-vector routing protocol. Both OSPF and IS-IS are examples of an Interior Gateway Protocol (IGP) that may be used for routing information within a domain or autonomous system (AS). In contrast, an Exterior Gateway Protocol (EGP) may be used for determining network reachability between autonomous systems and makes use of IGPs to resolve routes within an AS.
In a link-state routing protocol based network, each switching node (i.e., nodes or elements that are configured to forward packets, also known as routers) constructs a map of the connectivity of the network, in the form of a graph, showing which nodes are connected to which other nodes. Each node then independently calculates the best paths from that node to every possible destination in the network (e.g., using Dijkstra's algorithm), the collection of which forms the node's routing table or database.
To achieve scalability as well as simplify router design and operation, a hierarchical routing architecture may be utilized in a routing network. For example, a domain or AS—which is a portion of the network that may be under a common administrative authority—may be organized such that one or more areas may be defined within the domain or AS. In general, an area may be a logical entity that is comprised of a set of contiguous routers and the data links that connect them. All routers in the same area exchange information about all the hosts or End Systems (ESs) they can reach. The areas of an AS or domain are connected to form a backbone, wherein the routers have the information how to reach all areas.
Routers that can communicate within the same area are designated as Level 1 (L1) routers. Routers that form the backbone and have the information to reach other areas are designated as Level 2 (L2) routers. Some routers may be configured to operate as both L1 and L2 routers (L1L2) and may therefore be provided with routing databases specific to both intra-area and inter-area routing. Referring now to the drawings and more particularly to
For purposes of effectuating an operative routing network, each of the IS-IS routers engages in appropriate data exchange processes and maintains a number of databases that can be arranged in any known or heretofore unknown architectures. A unit of data, defined as a protocol data unit (PDU), may be regarded as a packet that is used for exchange of data. Four general types of packets exist, depending on the function of the PDU. A Link State Protocol Data Unit (LSP) is used for distributing link state information relative to the physical links (e.g., broadcast or point-to-point links) supported by the routers of the network. An IS-IS Hello (IIH) PDU is used for establishing and maintaining neighbor relationships (i.e., adjacencies) among the routers of the network, wherein an adjacency refers to a relationship between two IS-IS routers if they can perform a two-way communication with each other. Special PDUs known as Sequence Number PDUs (SNPs) may be used for purposes of link state database synchronization among the IS-IS routers. A Partial Sequence Number PDU (PSNP) is used to acknowledge and request link state information among the routers. A Complete Sequence Number PDU (CSNP) is used to describe a router's complete link state database. Depending on the size of a link state database associated with an IS-IS router, more than one CSNP may be needed to transmit the entire contents of the link state database in certain implementations.
Because of the hierarchical routing architecture of an IS-IS network, such as the network 100 exemplified in
After the IIH PDUs are exchanged and adjacencies are established in the IS-IS network, LSPs may be transmitted by the routers on all known links or interfaces (i.e., flooding) to exchange network topology information. In general, LSPs have a fixed header and one or more variable length content fields that are encoded using Type, Length and Value (TLV) coding. The fixed header may contain the PDU type/length, the LSP ID and sequence number, checksum, hierarchical level of the LSP (i.e., L1 or L2), among others. The TLV-coded contents may comprise the issuing IS router's area addresses, neighbor IS routers, neighbor ES routers, authentication information, etc.
To support enhanced functionalities such as Non Stop Routing (NSR), Stateful Switch Over (SSO), In-Service Software Upgrades (ISSU), and the like, any of the IS-IS routers exemplified in the IS-IS network 100 of
It should be appreciated that in order to support enhanced functionality such as, e.g., NSR, SSO, etc., the database(s) of a standby IS-IS hardware platform (which may be referred to as a route processor (RP) module) associated with an inactive IS-IS routing process must be maintained as current as possible relative to the database(s) of the active RP module executing the active IS-IS routing process, should it be necessary for any reason that the active IS-IS routing process cease its control plane execution and an inactive IS-IS routing process on the standby RP module take over the control. For example, to provide Non Stop Routing in a failover or in an operator-induced switchover scenario, the link state database of the active RP module (or, more generally an active router) must be accurately synchronized to the database(s) of the standby RP module (or, more generally a standby router) so that when the standby IS-IS router becomes the active IS-IS router, the active IS-IS router has a complete database to function seamlessly.
Those skilled in the art will recognize upon reference hereto that an IS-IS router architected with redundancy may be deployed to include a system of two or more RP modules, at least one of which is in an active mode and the remaining being in a standby mode. Accordingly, references to an “active IS-IS router” may mean an active RP module and references to a “standby IS-IS router” may mean a standby RP module in certain embodiments for purposes of the present patent disclosure.
Regardless of the approach used to synchronize the link state database(s), both local LSPs (i.e., LSPs generated by an RP module of the IS-IS router and remote LSPs (i.e., LSPs originated by other IS-IS routers) received by the IS-IS router must be synchronized between the active and standby RP modules in order to facilitate NSR. Typically, the local LSPs may be generated by an active RP module supporting an active IS-IS process based on the control information, status information, configuration data or updates thereof received from various hardware/software modules associated with the active RP module, including, e.g., line cards, ports, link interfaces, etc. Adding NSR functionality implies that when a standby RP module and the standby IS-IS process supported thereon are activated to become the new active RP module, the new active IS-IS process must also eventually generate LSPs describing the IS-IS router's link states based on the contents of its link state database. Furthermore, if a local LSP generated by the new active RP module is identical to the one generated by the old active RP module of the IS-IS router, that is, it has an identical checksum, then it would be preferable if the sequence number of such a local LSP remains the same and is handled in such a way that the switchover from the old active RP module to the new active RP module of the IS-IS router is transparent to neighboring routers. Clearly, accomplishing such a task requires certain link state data to be on or otherwise available to the standby RP module prior to it becoming the new active RP module of the IS-IS router. Likewise, remote LSPs received from the adjacent routers by the active RP module of the router (which contain the sending/originating router's internal information including its own link state data) are also required to be synchronized to the standby RP module's database.
Taking reference to
The link data base 208A associated with the active IS-IS process module 206A may be partitioned into separate database portions, e.g., one for storing and maintaining local LSPs and the other for storing and maintaining remote LSPs received from other routers. Reference numeral 211A refers to a first local LSP database portion wherein the locally generated LSPs are stored that may be refreshed or updated based on the configuration data inputs received from the modules 217. Reference numeral 213A refers to a first remote LSP database portion for storing the remote LSPs received from adjacent routers. As these remote LSPs are originated by other routers, which also operate according the IS-IS specification, the remote LSPs contain remote routers' information (link states and other data internal to the remote routers) encoded in the packet format specified by the IS-IS specification. The active IS-IS process module 206A therefore receives the remote LSPs in a raw LSP packet format according to the IS-IS specification, which are stored in the first remote LSP database portion 213A. One skilled in the art will recognize that the raw LSPs received from a remote router are in a format identical to that of the local LSPs generated and flooded to other routers, but contain different information describing the link state data of the originating remote router.
Similar to the active link state database 208A associated with the active IS-IS process module 206A, the standby or second link state database 208B associated with the standby IS-IS process module 206B may also be partitioned into separate local LSP and remote LSP database portions. Reference numerals 211B and 213B refer to example second local LSP and second remote LSP database portions, which are referred to herein as “second” database portions solely to distinguish from the corresponding database portions of the active or first link data base 208A. Although the standby IS-IS process module 206B is in a standby or inactive mode with respect to the control plane of the IS-IS router 200, it may be configured to perform certain limited functions in the “background,” and may therefore receive configuration data inputs from the modules within the router as well. Accordingly, in one example implementation, such data may be used by the standby IS-IS process module 206B to generate, refresh or otherwise update its own local LSPs. Regardless of whether the standby IS-IS process module 206B generates its own local LSPS, the second local LSP and second remote LSP database portions 211B, 213B may be synchronized to the corresponding first local LSP and first remote LSP database portions 211A, 213A, mediated by way of an inter-process communication and synchronization module 209 operatively coupled between the active (i.e., first) and standby (i.e., second) IS-IS process modules 206A, 206B. To facilitate such inter-process communication functionality for effectuating LSP database synchronization, an Active NSR Send module 207A interfaced with the active IS-IS process module 206A may be provided as part of the active RP module 202A and a Standby NSR Receive module 207B interfaced with the standby IS-IS process module 206B may be provided as part of the standby RP module 202B, wherein the inter-process communication module 209 is disposed in a communication relationship with both modules 207A, 207B.
One skilled in the art will recognize that the functionalities relating to NSR capability and facilitating LSP database synchronization may be advantageously grouped into one or more logical blocks in one example implementation, such as modules 209, 207A and 207B set forth above, that may comprise suitable hardware and/or software including storage media having computer-executable instructions.
Referring in particular to
The internal data received and processed with respect to the active IS-IS process module may be utilized in updating its local LSPs and hence the link state database associated therewith (block 406). Subsequently, the active IS-IS process module is required by the IS-IS specification to flood such local LSP updates to neighboring routers with which two-way communication has been established (i.e., adjacencies) (block 408). Further, as described in the foregoing sections, the active IS-IS process module is also required to synchronize the local LSP updates, in the identical format as in block 408, to the standby IS-IS process module in accordance with the teachings of the present patent disclosure (block 410). The standby IS-IS module subsequently updates its link state database with the updated local LSPs once they are received from the active IS-IS process module (block 412).
Those skilled in the art will recognize that the embodiments of the present disclosure can advantageously reduce the software code necessary for database synchronization in conventional router implementations because they typically involve two separate approaches for synchronizing local LSPs and remote LSPs between the redundant platforms. In other words, two sets of significantly different code are created and maintained in order to synchronize a link state database of the conventional IS-IS router, thereby increasing the amount of time and complexity needed to process the data. In the example embodiments of the present disclosure, on the other hand, the synchronization code is consistent and/or substantially same for synchronizing both local and remote LSPs between the platforms, resulting in a code that may be reduced as much as by half. Accordingly, the response time of the new activated IS-IS process module of a router undergoing the switchover may be significantly improved because using the raw LSP packets means that routes can be calculated immediately. As a consequence, inter-router database exchange can also occur immediately such that any detrimental effects and associated routing instabilities caused by route removal and insertion in a network domain can be mitigated. Furthermore, having the standby IS-IS process module maintain internal configuration/status control information sent by the active IS-IS process can be problematic in cases where the standby IS-IS process module obtains the same internal information from other standby components. In such cases, the only viable approach in conventional implementations is generally to abandon one copy of the information, resulting in unnecessary and duplicative work, which is alleviated and/or obviated by the example embodiments of the present patent disclosure.
It should be appreciated that when a standby IS-IS process of the router becomes a newly activated IS-IS process because of a switchover (e.g., including a failover condition), the newly activated IS-IS process has both the local and the remote LSPs that were sent by the previous active IS-IS process. Additionally, the newly activated IS-IS will also receive data from other newly activated modules pursuant to the switchover. In one implementation, when the router stabilizes or when a pre-defined checkpoint occurs, the newly activated IS-IS process may validate the synchronized local LSP with its internal data by attempting to generate a new copy of the local LSP (i.e., a new local LSP copy) using its internal data and comparing the checksums of the two copies of the local LSP. If the checksums are identical, then the newly activated IS-IS process determines that the synchronized local LSP is still current and valid. Consequently, the local LSP is not updated unnecessarily and the synchronized local LSP may be retained for use by the IS-IS router. As a further variation in this scenario, the new local LSP may be discarded by the newly activated IS-IS process since it is not needed. On the other hand, if the checksums do not match, then the newly activated IS-IS process determines that the synchronized local LSP needs to be updated and flooded to its adjacent neighbors.
In the foregoing Detailed Description, functionalities of the various elements including components/blocks labeled or described as “module” or “process” or “processor” or “controller” or “computer” may be provided through the use of dedicated hardware as well as hardware capable of executing stored or preconfigured software. When provided by a processor, the functions may be provided by a single dedicated processor, by a single shared processor, or by a plurality of individual processors, some of which may be shared or distributed. Moreover, a “processor” or “controller” may include, without limitation, digital signal processor (DSP) hardware, ASIC hardware, read only memory (ROM), random access memory (RAM), and/or other storage media. In a further variation, the NSR and LSP database synchronization functionality set forth in the foregoing embodiments may be downloaded, uploaded, or otherwise imparted to an existing IS-IS router that does not already have a dedicated module (such as, e.g., the inter-process communication/synchronization module 209) so as to enhance its performance.
Although various embodiments have been shown and described in detail, the claims are not limited to any particular embodiment or example. None of the above Detailed Description should be read as implying that any particular component, element, step, act, or function is essential such that it must be included in the scope of the claims. Reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather “one or more.” All structural and functional equivalents to the elements of the above-described embodiments that are known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the present claims. Accordingly, those skilled in the art will recognize that the exemplary embodiments described herein can be practiced with various modifications and alterations within the spirit and scope of the claims appended below.
This nonprovisional application claims priority based upon the following prior United States provisional patent applications entitled: (i) “IS-IS NON STOP ROUTING COMPLETE SEQUENCE NUMBER PROTOCOL (CSNP) DATA UNIT FOR LINK-STATE PROTOCOL (LSP) DATA UNIT RECOVERY AND GRACEFUL RESTART,” Application No. 61/730,778, filed Nov. 28, 2012, in the name(s) of Wenhu Lu, Thippana Hongal and Ing-Wher Chen; (ii) “IS-IS NON-STOP ROUTING (NSR) RAW LINK-STATE PROTOCOL (LSP) DATA UNIT SYNCHRONIZATION,” Application No. 61/730,784, filed Nov. 28, 2012, in the name(s) of Wenhu Lu, Ing-Wher Chen and Thippana Hongal; and (iii) “METHOD AND APPARATUS FOR NON-STOP ROUTING FOR PROCESS RESTART,” Application No. 61/730,796, filed Nov. 28, 2012, in the name(s) of Wenhu Lu, Ing-Wher Chen and Thippana Hongal; each of which is hereby incorporated by reference in its entirety. This application discloses subject matter that is related to the subject matter of the following U.S. patent application(s): (i) “METHOD AND APPARATUS FOR PROTOCOL DATA UNIT RECOVERY IN AN IS-IS SYSTEM” (Ericsson Ref. No.: P38850-US2), application Ser. No. ______, filed ______, in the name(s) of Wenhu Lu, Thippana Hongal and Ing-Wher Chen; (ii) “METHOD AND APPARATUS FOR FACILITATING PROCESS RESTART IN AN IS-IS SYSTEM” (Ericsson Ref. No.: P38916-US2), application Ser. No. ______, filed ______, in the name(s) of Wenhu Lu, Ing-Wher Chen and Thippana Hongal; and (iii) “METHOD AND APPARATUS FOR FACILITATING PROCESS RESTART IN A MULTI-INSTANCE IS-IS SYSTEM” (Ericsson Ref. No.: P40160-US1), application Ser. No. ______, filed ______, in the name(s) of Wenhu Lu, Ing-Wher Chen and Thippana Hongal; each of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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61730778 | Nov 2012 | US | |
61730784 | Nov 2012 | US | |
61730796 | Nov 2012 | US |