Patent Publication Number: US-2007104198-A1

Title: Apparatus and method for providing a high availability network mechanish

Description:
TECHNICAL FIELD  
      This invention relates generally to networks and more specifically to high availability networks.  
     BACKGROUND  
      Many types of networks for sharing and routing information are known. Typically, networks are designed with a group of computers or servers linked together using a common protocol for sending information through the network. A common protocol for linking computers through a network is the Internet Protocol (“IP”). A problem with such networks includes the need to have the networks operating with very little downtime such that information is reliably and quickly transferred within the network. For example, networks for live sharing of information such as communication networks require high reliability both for prompt sending of information and for quickly adjusting to failures within the network. Different protocols have been developed for sharing information within typical IP networks. These protocols have different strengths and weaknesses depending upon the network in which these protocols are applied.  
      One known protocol is the Virtual Router Redundancy Protocol (“VRRP”). This protocol provides redundancy within a network such that if a given computer fails, the network will not fail. VRRP is typically utilized within a given group of computers such that if a primary computer within the group fails, another computer is automatically designated the primary computer for the group thereby reducing the time necessary to reestablish the group&#39;s functionality and/or connection to another computer or network. Such reestablishment of a network is typically called a re-convergence.  
      Another known protocol is the Open Shortest Path First (“OSPF”) protocol. The OSPF protocol is typically implemented within networks where multiple paths for sharing or sending information are available. The OSPF operates by determining the cheapest route through the network for transmitting information, based on the number of resources used to transmit the information. A network using OSPF periodically recalculates the costs for sending information between various computers, servers, or nods within the network such that when information needs to be sent, the lowest cost route is typically readily known and utilized. If a computer or server within a network utilizing OSPF fails, the network would recognize this and re-determine the lowest cost routes for sending information, thereby establishing re-convergence of the network. Given the different types of networks within which OSPF and VRRP typically operate, it is difficult to achieve the benefits of both protocol types. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The above needs are at least partially met through provision of the apparatus and method for providing a high availability network mechanism described in the following detailed description, particularly when studied in conjunction with the drawings, wherein:  
       FIG. 1  is a block diagram as configured in accordance with various embodiments of the invention; and  
       FIG. 2  is a flow chart as configured in accordance with various embodiments of the invention.  
      Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions and/or relative positioning of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of various embodiments of the present invention. Also, common but well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention. It will further be appreciated that certain actions and/or steps may be described or depicted in a particular order of occurrence while those skilled in the arts will understand that such specificity with respect to sequence is not actually required. It will also be understood that the terms and expressions used herein have the ordinary meaning as is accorded to such terms and expressions with respect to their corresponding respective areas of inquiry and study except where specific meanings have otherwise been set forth herein. 
    
    
     DETAILED DESCRIPTION  
      Generally speaking, pursuant to these various embodiments, a high availability network mechanism is provided with a primary node utilizing a VRRP compatible redundancy system and a secondary node utilizing a VRRP compatible redundancy system. The primary node and secondary node access a core IP network through first and second edge routers such that a virtual IP address is associated with both the primary node and the secondary node with a first cost assigned to the primary node and a second cost assigned to the secondary node. The core IP network utilizes an OSPF compatible redundancy system for managing the routing of information through the network.  
      So configured, the high availability network gains the redundancy advantages of VRRP within the nodes of the network in addition to the redundancy advantages of OSPF in the overall network. By combining the advantages of the two redundancy systems, the network can achieve re-convergence very quickly in the event of local failure of the primary computer within a node and in the event of a catastrophic failure of an entire node. Further, because VRRP and OSPF are both standards compliant protocols, the invention may be applied without excessive effort to bring the network up to applicable standards.  
      Referring now to the drawings, and in particular to  FIG. 1 , a high availability network mechanism  100  includes a primary node  105  utilizing a VRRP compatible redundancy system. A node is typically one or more computers having a single access to a network. The primary node  105  is associated with at least one first access router  110  with a unique physical IP address. The first access router  110  is associated with a first edge router  115 . A secondary node  120  also utilizes a VRRP compatible redundancy system and is associated with at least one second access router  125 . A second edge router  130  is associated with the secondary node  120 . A core IP network  135  is accessible through the first edge router  115  and the second edge router  130 .  
      A virtual IP address is associated with the primary node  105  and has a first cost assigned to the primary node  105 . The same virtual IP address is associated with the secondary node  120  and has a second cost assigned to the secondary node  120 . The core IP network  135  then uses the virtual IP address within an OSPF compatible redundancy system within the network  135 .  
      In an alternative embodiment, the primary node  105  includes a plurality of sub-nodes  140  and  145 . Typically, each sub-node  145  will be associated with a separate first access router  150  with a different unique physical IP address such that one sub-node  140  and its first access router  110  will have a different physical IP address from another sub-node  145  and its first access router  150 .  
      Similarly, the secondary node  120  may include a plurality of sub-nodes  155  and  160 . Typically, each sub-node  160  will be associated with a separate first access router  165  with a different unique physical IP address such that one sub-node  155  and its second access router  125  will have a different physical IP address from another sub-node  160  and its second access router  165 .Typically, each access router for a node will be associated with the edge router for that node. Thus, the first access routers  110  and  150  are associated with the first edge router  115 , and the second access routers  125  and  165  are associated with the second edge router  130 . With this configuration, the same virtual IP address can apply to the entire primary node sub-system including for example the primary node&#39;s access routers, collectively designated as reference numeral  170 , and to the entire secondary node sub-system including for example its access routers, collectively designated as reference numeral  175 , despite the various physical IP addresses used by the various access routers.  
      One should note that in the typical hierarchical arrangement of the network, then, the nodes  105 ,  120 , and  190  each utilize a VRRP compatible redundancy system such that the VRRP compatible configure compensates for failures within a node  105 ,  120 , or  190 . At the higher level, within the IP network  135 , an OSPF compatible redundancy system operates to compensate for total failures of a primary node  105 . In other words, the combination and hierarchy can be arranged as nodes that are part of two or more autonomous systems. The VRRP compatible redundancy system can be configured between sub-nodes within a node  105 ,  120 , or  190  that will use a default gateway redundantly to one or more autonomous systems to provide reachability to an external network such as the IP network  135 . The OSPF compatible redundancy system will be configured as the transport routing protocol on access routers and all core external edge routers that will convey information about the highly available IP addresses and corresponding functionalities. Thus, in terms of configuration hierarchy, end nodes that are part of a single LAN within a geographical area can be setup to run a VRRP compatible redundancy system and the rest of the network that includes devices/routers with multiple LAN segments or subnets can be configured to run OSPF. Thus, the VRRP and OSPF compatible redundancy systems operate together at different hierarchical portions of the overall network to provide increased redundancy for the overall network.  
      Therefore, within each node  105  or  120 , the plurality of sub-nodes  140  and  145  or  155  and  160  provides n+1 redundancy within the nodes  105  and  120  through the application of the VRRP compatible redundancy system. Thus, should the main sub-node  140  for the primary node  105  fail, sub-node  145  automatically assumes the connection for the node  105 . Typically, when the primary node  105  experiences such a single failure, the primary node  105  will achieve re-convergence within less than about 20 milliseconds. Such a re-convergence time is determined based upon typical re-convergence times for VRRP only based networks. Typically, a VRRP compatible redundancy system also has a “Master Down Interval” time that forces re-convergence in the order of about 1 second. There are certain known system configurations also available that affect the re-convergence times to some extent, but the integration of physical link detect type mechanisms significantly reduce detect times so that the re-convergence in the VRRP compatible redundancy system is triggered immediately without having to wait for the typical interval to expire thereby achieving re-convergence times of less than about 20 milliseconds.  
      Further, the OSPF compatible redundancy system used within the core IP network  135  provides an n+1 redundancy for the primary node sub-system  170  where each secondary node sub-system  175  associated with the primary node sub-system&#39;s  170  virtual IP address provides that redundancy. Such redundancy among the nodes&#39; sub-systems  170  and  175  allows for protection against a catastrophic failure of an entire node or node sub-system such as failure of a node&#39;s access or edge routers. For example, a typical high availability network mechanism  100  can be applied on a large geographic scale where the primary node sub-system  170  can be located in Los Angeles and the secondary node sub-system  175  can be located in Atlanta. Another edge router  180  may provide access to the core IP network  135  for another node such as a radio access network  185  located in Phoenix.  
      Typically, the radio access network  185  in Phoenix is more likely to receive its data from the primary node sub-system  170  in Los Angeles because the cost to receive such data through the IP network  135  from the primary node sub-system  170  will typically be less than the cost to receive such data from the secondary node sub-system  175  in Atlanta. Should the primary node sub-system  170  in Los Angeles experience a catastrophic failure, such as in the event of an earthquake, the radio access network  185  in Phoenix will be able to receive data from the secondary node sub-system  175  in Atlanta because the OSPF redundancy system in the IP network  135  will reset the cost for the primary node sub-system  170  to indicate that the node is offline. Then, the IP network  135  will recognize the virtual IP address and smallest cost as that of the secondary node sub-system  175  in Atlanta and reroute all information to the radio access network  185  through the secondary node sub-system  175 . Usually, such re-convergence of the high availability network mechanism upon a catastrophic failure of the primary node sub-system  170  occurs in less than about 45 seconds.  
      Such a re-convergence time is determined based upon typical re-convergence times for OSPF only based networks. Typically, the OSPF protocol depends upon a “router dead interval” to detect and trigger re-convergence in a network. The overall re-convergence time is dependent upon the size and number of routers in the network, but typically this is typically less than about  45  seconds and more often in the order of about 20 to 30 seconds. There are certain known system configurations also available that affect the re-convergence times to some extent, but the integration of physical link detect type mechanisms and fast-LSA (“Link State Algorithm”) techniques significantly reduce detect times so that the re-convergence in the OSPF compatible redundancy system can be achieved in less than about 10 seconds.  
      In certain embodiments, the virtual IP address can be adapted to various specific uses. For example, in a given system a virtual IP address may be associated with a given functionality. Such functionalities may include transferring voice data, transferring text messaging data, signaling and associated control data for call processing applications, or other such functionalities. Similarly, the virtual IP address may be associated with a given application. For example, a single virtual IP address may be exclusively identified with a particular gaming application, paging applications, and applications to provide on-demand network level statistics, network control, and traffic engineering. These associations between functionality or application and virtual IP address allow for easier maintenance and managing of the network and easier creation of the proper redundancy for certain applications or functionalities.  
      In one such embodiment, the high availability network mechanism may include a plurality of virtual IP addresses assigned to the secondary node  120  wherein each virtual IP address is associated with one of a plurality of primary nodes  105  and  190 . In this alternative, the secondary node  120  may be a redundant backup for any number of primary nodes  105 . Each primary node  105 , therefore, may be associated with a different functionality or application, and the secondary node  120  may operate as a redundant backup for all those functionalities or applications. In accordance with this embodiment, each virtual IP address assigned to the secondary node  120  will have an associated second cost that is typically higher than the first cost associated with the primary node  105  for that virtual IP address. Thus, in this embodiment, the secondary node  120  provides geographical redundancy for multiple different functionality groups of primary nodes  105 .  
      Alternatively, a single primary node  105  may have a plurality of secondary nodes  120  and  190  that are assigned the primary node&#39;s  105  virtual IP address and with second costs associated with the secondary nodes  120 . In this embodiment, the primary node  105  has multiple redundant backup nodes  120  and  190 . The second costs may be assigned to the secondary nodes  120  and  190  automatically or set by a network administrator to create a priority among the backup secondary nodes  120  and  190 . Thus, one should note that using the same virtual address for multiple nodes with different costs for each node within the network using the OSPF compatible redundancy system provides flexibility in the design of the network and significant advances in the recovery of the network in the event of node failure.  
      A method of providing a high availability network mechanism will be discussed with reference to  FIG. 2 . Starting with the nodes, one utilizes  205  a VRRP compatible redundancy system within the primary node  105  and utilizes  210  a VRRP compatible redundancy system within the secondary node  120 . A first unique physical IP address is assigned  215  to a first access router  110  associated with the primary node  105 , and a second unique physical IP address is assigned  220  to a second access router  125  associated with the secondary node  120 . The first access router  110  is associated  225  with the first edge router  115 , and the second access router  125  is associated  230  with the second edge router  130 . A virtual IP address with a first cost is assigned  235  to the primary node  105 . Similarly, the virtual IP address assigned to the primary node  105  is assigned  240  to the secondary node  120  but with a second cost.  
      Typically, each cost is assigned by automatically assigning the costs based upon a provided decision process algorithm. For instance, it is common for a network using OSPF to include an internally operated algorithm that periodically detects the system costs for routing information between given nodes. Costs can be assigned based upon path preference, bandwidth availability, node reliability, or any of several other known pre-determined factors. Once the cost has been assigned to a virtual IP address, when the virtual IP address is learned by the network, the cost associated is also inherently learned. Thus, because the typical routing database for the IP network includes multiple routes to a given network functionality or application, the IP network essentially immediately knows what the next best path is when one of the nodes goes down and uses that next best path to achieve higher availability. Such algorithms or similar readily developed algorithms may determine and assign the costs to the primary node  105  and secondary node  120 . Alternatively, a network administrator may preset the costs so as to determine the hierarchy of the nodes within the OSPF compatible redundancy system.  
      Similarly, assigning  235  and  240  the virtual IP address typically includes automatically assigning the virtual IP address based upon a provided software algorithm. The software algorithm is typically an algorithm built within the network  135  running the OSPF compatible redundancy system such that once a network administrator sets that a particular node should be assigned a virtual IP address, the software based network algorithm sets the IP address automatically. Alternatively, the network administrator may preset the virtual IP addresses for the nodes of the network.  
      In a further alternative, the virtual IP address may be assigned to a given functionality or a given application. Such an assignment is usually done by a network administrator either by specifically assigning a virtual IP address to a given functionality or application or by designating within the network  135  that a given functionality or application is to assigned a particular virtual IP address.  
      In an alternative to assigning  240  the virtual IP address to the secondary node  120 , a plurality of virtual IP addresses may be assigned to the secondary node  120  wherein each virtual IP address is associated with one of a plurality of primary nodes  105  and  190 . In this alternative, each virtual IP address has an associated second cost that is associated with the secondary node  120 .  
      With continuing reference to  FIG. 2 , a core IP network  135  is provided  250  that is accessible through the first edge router  115  and the second edge router  130 . Further, an OSPF compatible redundancy system is utilized  260  within the core IP network  135 . The virtual IP address is then advertised  270  to the core IP network  135 . Advertising an IP address is known within OSPF compatible redundancy systems where a node advertises the IP address for the node to the network for routing and for cost calculating purposes.  
      In an alternative embodiment, a plurality of nodes is provided wherein each of the plurality of nodes  190  is geographically separate, utilizes a VRRP compatible redundancy system, and is assigned the virtual IP address when the plurality of nodes  190 , the primary node  105 , and the secondary node  120  share at least the same functionality or the same application. Such a provided larger scale network will usually allow for increased ease in managing the high availability network mechanism  100  where a single virtual IP address is assigned to a given functionality or application.  
      One skilled the in art will recognize that the various servers, computers, and networking hardware needed to construct such network mechanisms as described herein are known and readily available. One skilled in the art would be able to reconfigure the software controls for these hardware components to implement the systems as described. Further, one will recognize that although VRRP and OSPF are standards based systems, similar or compatible systems or future modifications to these systems would be similarly functional within the described network mechanisms.  
      So configured, the above described networks provide n+1 redundancy within the nodes of the network and within the individual nodes. Thus, re-convergence times for various failure modes within such a network and within the nodes are typically reduced. Further, because the described networks operate under standards based protocols, implementation typically requires less up front effort and cost. In addition, application or functionality specific addresses provide additional ease in network maintenance and development.  
      Those skilled in the art will recognize that a wide variety of modifications, alterations, and combinations can be made with respect to the above described embodiments without departing from the spirit and scope of the invention. For example, one skilled in the art will recognize that the above described high availability network mechanism concepts may further be applied larger scale and more complicated networks. Such modifications, alterations, and combinations are to be viewed as being within the ambit of the inventive concept.