Abstract:
The present invention utilizes Virtual Internet Protocol Addressing (VIPA) to enable a host computer to efficiently route TCP/IP traffic across multiple physical links. This is accomplished by associating different applications or application sets with different virtual IP addresses. The virtual IP addresses may be associated with different physical adapters. Since many applications send similar data repeatedly, categorizing application sets and associating them with different physical adapters allows high volume applications to be associated with one adapter while lower volume, interactive data is associated with another adapter.

Description:
BACKGROUND OF THE INVENTION 
     TCP/IP (Transmission Control Protocol/Internet Protocol) is the transport mechanism underlying the Internet. It is also the underlying protocol for many intranets and business applications in existence today. TCP/IP was started as an educational and scientific network. It was not designed to handle high-volume traffic associated with a mixture of applications that have different service level requirements. Because of this design point, there were few effective measures incorporated into TCP/IP to handle applications with conflicting service level requirements. 
     Through the growth of the Internet, which includes the world wide web, requirements have arisen for better control of service levels for host TCP/IP networks. This has become especially true where the TCP/IP host controls business applications or transactions. The design of TCP/IP is such that each physical network interface adapter has associated with it an address. This is unique within the entire network and is the method by which all other devices communicate with the adapter or the devices connected through the adapter. If a given TCP/IP host has multiple interface adapters, the user communicating with the host must select an interface adapter which they chose to use. The user must then reference the host by the address of the particular adapter which the user has chosen to use. After the routing protocols have converged all the routing tables contained within hosts and routers throughout the network, they all will agree on one route for datagrams from one address on one host to one address on another host. 
     The above method works well when all applications executing on a given host at one time require the same level of service, or when the interface adapters are not highly utilized, or when the host has only one network interface adapter. However, in many cases a large host system simultaneously executes multiple applications with different service level requirements, has more than one interface adapter available, and highly utilizes some of those interface adapters. For example, when a file transfer protocol (FTP) server is transmitting enough traffic to almost fully utilize some network interface adapters on a host, TELNET (interactive) connections to that server that use those same highly utilized links may suffer from unacceptable interactive response time, because TELNET traffic may have to wait for the transmission across the network interface adapters of the much more voluminous FTP traffic. 
     Two methods have been proposed for dealing with different service level requirements in a TCP/IP host. First, the Internet Protocol header includes a field with which the host can indicate the type of service requested for the datagram associated with this header. If the Minimum Delay bit in that field is turned on, then all hosts and routers transmitting the datagram should try to transmit it with minimum delay. If the Maximum Throughput bit in that field is turned on, then all hosts and routers should try to transmit it via the highest bandwidth path available. (The header of an IP datagram should not have both the Minimum Delay and the Maximum Throughput bits turned on.) For example, if a host has two links, one a low-bandwidth terrestrial link and the other a high-bandwidth satellite link, the administrator may prefer for high-bandwidth FTP traffic to use the high-bandwidth satellite link despite its inherent delay, and for low-bandwidth but interactive TELNET traffic to use the inherently lower-delay terrestrial link. However, since very few hosts or routers consider the settings of these bits when making routing decisions, turning on either of these bits is not usually an effective procedure. For additional information on the minimum delay bit and the maximum throughput bit see RFC 791, &#34;Internet Protocol&#34;. 
     The second method for addressing the problem is for some hosts have one output queue for datagrams from interactive applications, such as TELNET and rlogin, and another output queue for datagrams from all other applications, including FTP, and have the network interface layer assign datagrams to queues according to the datagram&#39;s TCP port number. In some cases, these hosts send out all the datagrams from the interactive queue before sending out any from the non-interactive queue. However, by forcing the high-bandwidth traffic to wait to use the same physical interface adapter as the low-bandwidth traffic, this process results in low throughput if the adapter is slow, or low utilization if the adapter is fast. Network administrators would prefer to have the more voluminous FTP traffic fully utilize a higher-bandwidth (and therefore more expensive) adapter, and have the less voluminous TELNET traffic experience smaller delays over a less highly utilized low-bandwidth adapter, where the lower utilization would matter less because the low-bandwidth adapter is less expensive. Current TCP/IP software limitation do not support traffic splitting, even in the presence of multiple network interface adapters that can reach a common destination. Therefore multiple queues for this purpose, in addition to multiple routes to a common destination are not allowed in the present implementation of TCP/IP. These limitations lead to traffic bottlenecks at the network interface adapters. 
     RELATED APPLICATIONS 
     Related applications describing the Virtual IP Addressing (VIPA) technology are: 
     Application Ser. No. 08/755,420 entitled &#34;Virtual Internet Protocol (IP) Addressing&#34; filed on Nov. 22, 1996 and assigned to IBM Corp., now pending; and, 
     Application Ser. No. 08/761,469 entitled &#34;Host Identity TakeOver Using Virtual Internet Protocol (IP) Addressing&#34; filed on Dec. 6, 1996 also assigned to IBM Corp, now pending. 
     SUMMARY OF THE INVENTION 
     The present invention allows the administrator of a host that has multiple network interface adapters to associate each desired subset of applications with a virtual IP address (VIPA) and then configure the host to advertise a route to each such VIPA over a different real physical network interface adapter. This causes traffic for each subset of applications to be transmitted over a different real physical network interface adapter, which the network administrator can select to have bandwidth and delay characteristics that match the application. Therefore, if interactive applications such as TELNET are associated with one VIPA address, and high-bandwidth applications such as FTP are associated with another VIPA, then the voluminous FTP traffic can be segregated to one real physical network interface adapter so that it will not interfere with the interactive response time of the TELNET traffic that is segregated onto a different real physical network interface adapter. Furthermore, this host can be configured such that when a real physical network interface adapter fails, another one can serve as a backup by integrating the different subsets of traffic for the duration of the link failure. 
     Without significantly increasing the cost of the network, this invention enhances the performance of a TCP/IP network using hosts with multiple or redundant devices or network interface adapters by eliminating the time that one class of application traffic must wait on another class of application traffic for transmission across network interface adapters, while also providing for backup during the failure of one or more real physical network interface adapters. This is accomplished by the use of a virtual device, a virtual adapter, a virtual IP address (VIPA), and Routing Information Protocol (RIP) route forwarding output filters. 
    
    
     DESCRIPTION OF DRAWINGS 
     In FIGS. 1 through 4 the host is assumed to have one application subset consisting of TELNET and another application subset consisting of FTP; note that there could be more application subsets, and that any application could belong to any application subset. 
     FIG. 1 depicts a representative network without session traffic splitting. 
     FIG. 2 demonstrates the logical flow of the transmission process with prior art. 
     FIG. 3 depicts the representative network with session traffic splitting. 
     FIG. 4 demonstrates the logical flow of the transmission process with session traffic splitting. 
     FIG. 5 shows a representative network in which the present invention may be implemented. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The preferred embodiment of the present invention is implemented in, but not limited to, an IBM MVS (501) host running the TCP/IP protocol and directly connected to a network (503) by two or more links (505) connected to the host through two or more adapters (507). This configuration allows for multiple virtual IP addresses, each of which selects a subset of TCP/IP applications executing on one TCP/IP stack in one host, to proceed without selecting a specific real physical network interface adapter or device. Other hosts that connect to one of the subsets of MVS TCP/IP applications executing on that host can send data to the MVS virtual IP address (VIPA) associated with that subset of applications via whatever paths are selected by the routing protocols. This is enabled by the use of RIP route forwarding filters. Transmission of traffic of one subset of applications between the host and the network will not interfere with transmission of traffic of another subset of applications. Furthermore, should the real physical network interface adapter that is transmitting traffic for a certain subset of applications fail, one of the other real physical network interface adapters can transmit the traffic in a backup mode, although during the outage traffic from different subsets of applications may be mixed. This is explained more completely by way of example in FIGS. 1 and 3. 
     The means of accomplishing this application categorization and VIPA association is to modify the configuration files of the host&#39;s TCP/IP software such that a route to a single VIPA address associated with a desired subset of applications is advertised by RIP (the TCP/IP Routing Information Protocol) only through a real physical network interface adapter specified in the configuration files. To segregate traffic of different subsets of applications, a different VIPA address is associated with each different subset of applications, and RIP is configured to advertise a route to each different VIPA over a different real physical network interface adapter. Furthermore, the host administrator can specify in the configuration files that if a link fails, traffic from the subset of applications that were using that link can share a real physical network interface adapter with traffic from another subset of applications for the duration of the failure. RIP is configured to perform these functions through the Route Forwarding (Conditional and Unconditional) options which provide route forwarding support as a means to filter routes to a particular interface. This can be useful in selecting certain routes to be broadcast over certain interfaces. Two options have been added to support conditional and unconditional route forwarding. With unconditional route forwarding, RIP will not forward routes to other interfaces in case of interface outages. With conditional route forwarding, a forwarded route is allowed to be broadcast over other interfaces throughout the duration of an allowed interface outage. After the failed interface returns to normal, RIP will resume route forwarding to the assigned interface. 
     FIG. 1 is a representative example of a network that does not use session traffic splitting while still implementing Virtual IP Addressing (VIPA). Host MVS --  M (101) has VIPA address VIPA --  M (106) by which all clients address host MVS --  M. Host MVS --  M is executing two applications, TELNET (102) and File Transfer Protocol (FTP) (103), both of which are running on the same TCP/IP stack (104). The TCP/IP stack uses the Network Interface Layer (105) to transmit datagrams to and from the IP Network (111). Within the Network Interface Layer the output queue OutQueue1 (107) holds datagrams ready for transmission across Link --  1 (109), and the output queue OutQueue2 (108) holds datagrams ready for transmission across Link --  2 (110). Both Link --  1 and Link --  2 connect to the IP Network. In this ex ample Client --  X (112) has connections to both TELNET and FTP via Link --  1, and Client --  Y (113) has connections to both TELNET and FTP via Link --  2. In both OutQueue1 and OutQueue2 Telnet datagrams may be waiting for transmission behind several FTP datagrams. 
     FIG. 2 demonstrates the process by which the prior art determines routes between MVS --  M and the clients Client --  X and Client --  Y such that each output queue contains datagrams from both TELNET and FTP. In this example, RIP will advertise routes to VIPA --  M over both Link --  1 and Link --  2 (201). In the present example, we assume that (ignoring service levels) the best route between VIPA --  M and Client --  X traverses Link --  1, and that the best route between VIPA --  M and Client --  Y traverses Link --  2. Therefore, after RIP has converged the routing tables throughout the IP network (202), datagrams from VIPA --  M to Client --  X will pass through Link --  1 and therefore through OutQueue1 (203). Likewise, datagrams from VIPA --  M to Client --  Y will pass through Link --  2 and therefore through OutQueue2 (204). Thus, while FTP is sending large files, the relatively small and infrequent TELNET datagrams will be enqueued behind FTP datagrams in both output queues, and therefore transmission of FTP datagrams will impact interactive response times of TELNET users (205). 
     FIG. 3 is a representative example of a network that uses session traffic splitting of the present invention. Host MVS --  M (301) is executing two applications, TELNET (302) and File Transfer Protocol (303), both of which are running on the same TCP/IP stack (304). The TCP/IP stack uses the Network Interface Layer (305) to transmit datagrams to and from the IP Network (312). Within the Network Interface Layer the output queue OutQueue1 (308) holds datagrams ready for transmission across Link --  1 (310), and the output queue OutQueue2 (309) holds datagrams ready for transmission across Link --  2 (311). Both Link --  1 and Link --  2 connect to the IP --  Network. Host MVS --  M has two VIPA addresses: VIPA --  T (306), which is associated with TELNET, and VIPA --  F (307), which is associated with FTP. In this example MVS --  M has TELNET connections with both Client --  X (313) and Client --  Y (314) via Link 1, and MVS --  M has FTP connections with both Client --  X and Client --  Y via Link --  2. OutQueue1 contains only TELNET datagrams, and OutQueue2 contains only FTP datagrams. The TELNET datagrams, which are destined to be transmitted across Link --  1, need not wait for the transmission of FTP datagrams across Link --  2. 
     FIG. 4 demonstrates the process by which this invention segregates all the TELNET datagrams in one output queue such that they are never queued behind FTP datagrams for transmission, which this invention segregates in another output queue. First, this process checks to determine if the administrator has configured session traffic splitting in the host by setting the RIP route forwarding output filter option (401). If not, the processing continues as in FIG. 1 without session traffic splitting (403). If session traffic splitting is configured, then a check is made to determine whether or not all the links are functioning (405). The different types of links are not limited to just terrestrial and satellite, but all imaginable forms of terrestrial and non-terrestrial links. If not, then the process checks whether or not the RIP route forwarding output filter option is conditional (407). 
     If conditional route forwarding is configured and some links are not functioning, then RIP in MVS --  M will advertise over the functioning link routes to both VIPA --  F and VIPA --  T (409). Therefore, after RIP has converged the routing tables throughout the IP network, datagrams from both FTP and TELNET in MVS --  M to any client will pass through the functioning link (411) and therefore through its output queue (413). This results in both the FTP and TELNET datagrams being placed into the same queue. Thus, while FTP is sending large files, the relatively small and infrequent TELNET datagrams will be enqueued behind FTP datagrams in that output queue, and therefore transmission of FTP datagrams will impact interactive response times of TELNET users (415) if the method for parsing the output queue is FIFO, as it is in most TCP/IP implementations. The process is then continued as before (417). 
     If unconditional route forwarding is configured and some links are not functioning, then RIP in MVS --  M will advertise over the functioning link routes to only the VIPA associated with the functioning link (419). Therefore, the routes propagate through the IP network such that, after RIP has converged the routing tables throughout the IP network, all clients send traffic to the VIPA associated with the desired application via the functioning link (421). Datagrams of the application bound to the VIPA associated with the functioning link will pass through the functioning link (423). Furthermore, after RIP has converged the routing tables throughout the IP network, datagrams of the application bound to the VIPA associated with the non-functioning link cannot be delivered (425). From this point, processing continues as before (427). 
     If the administrator has configured the RIP route forwarding output filter option, and all links are functioning then RIP in MVS --  M will advertise routes over their associated links (429). In the present example, MVS --  M will advertise routes to VIPA --  T only over Link --  1 and routes to VIPA --  F only over Link --  2 (431). Therefore, after RIP has converged the routing tables throughout the IP network all clients will send to the target applications via their associated link. In our particular example, a determination will be made as to whether or not the datagrams are TELNET datagrams (432). If the datagrams are from TELNET in MVS --  M they will pass through Link --  1 regardless of the associated client and therefore through OutQueue1 (433). Likewise, any datagrams not from TELNET, in our example, are FTP datagrams, whereby datagrams from FTP in MVS --  M to any client will pass through Link --  2 and therefore through OutQueue2 (435). Thus, even while FTP is sending large files, the relatively small and infrequent TELNET datagrams will not be enqueued behind FTP datagrams in the output queues, and therefore transmission of FTP datagrams will not impact interactive response times of TELNET users. From this point on the process continues as before (437).