Abstract:
The present invention provides automatic classification of an IPv6 packet to a given topology. A topology identifier is carried as an embedded field in the interface ID portion of an IPv6 address. Automatic classification of an IPv6 packet for a given topology prevents manual configuration in intermediate nodes. Further, it remedies the value limit problem of differentiated services code points (DSCPs) and re-use of DSCP values within each topology.

Description:
FIELD  
       [0001]     The present invention relates broadly to packet-switched networks. Specifically, the present invention relates to automatically configuring a router to send a received packet along a communication path to a logical topology identified within the packet.  
       BACKGROUND  
       [0002]     Multi-topology Routing (MTR) involves mechanisms that build multiple independent logical topologies on top of a physical topology, and classify and forward packets belonging to different topologies. Two processes are key to MTR. The first is an extension to Routing Protocol used to build multiple independent topologies. The other key process is the marking and classification of the packet as belonging to a given topology.  
         [0003]     Extension to routing protocols have already been defined in order to create multiple logical topologies. Marking the packet is required in order to be able to classify the packet as belonging to which topology so that the correct RIB could be used to forward the packet. There are not many choices in IP headers for marking a packet. Typically, a differentiated services code point (DSCP) is used in order to mark a packet. However, this approach suffers a significant shortcoming in that each node in the network has to consistently be configured in order to map the DSCP to the corresponding topology identified by multi-topology identifier (MT-ID). The problem with this approach is that not only does it require consistent mapping in all routers and is prone to misconfiguration, but DCSP values are limited and may be used for other purposes within a topology.  
       SUMMARY  
       [0004]     The present invention carries the topology that a packet belongs to as a MT-ID, as indicated in an embedded field within an IPv6 address. This allows the originator of the packet to set the MT-ID in the packet; all other routers automatically associate the packet to its corresponding topology, thereby reducing manual configuration and the possibility of any erroneous configuration. It is to be understood that routers used in embodiments of the present invention are multi-topology routing (MTR) aware, and IPv6 packets generated by an end host router are marked to indicate such a marking.  
         [0005]     In one aspect, the present invention provides a method of routing packets that belong to a logical network topology associated with a physical topology, by generating a packet having an IPv6 format with a multi-topology identifier (MT-ID) uniquely identifying a logical topology that is carried as an embedded field in the Interface ID part of the IPv6 address. IPv6 unicast addresses include a 64-bit interface identifier field in modified EUI-64 format, based on the IEEE EUI-64 (referred to herein as EUI64) specification. The modified EUI-64 format inverts the sense of the ‘u/l’ bit from its specification in EUI64, i.e., ‘u/i’=0 indicates local use. The Intra-site Automatic Tunnel Addressing Protocol (ISATAP) already specifies an EUI64-format address construction for the Organizationally-Unique Identifier (OUI) assigned by the Internet Assigned Numbers Authority (IANA). This format is used to construct both native EUI64 addresses for general use and modified EUI-64 format interface identifiers for use in IPv6.  
         [0006]     In another aspect, the present invention provides a method for routing packets that belong to a logical network topology, by receiving a packet having an IPv6 format with a MT-ID contained in its interface identifier field. Upon receipt by a router in accordance with the present invention, the MT-ID is read, and the router associates the received packet with the topology identified by the MT-ID by inspecting a local table that maps MT-IDs with logical topologies, and reading a routing table that determines where to send the received packet so that it reaches its logical topology.  
         [0007]     Other features and advantages of the present invention will be realized upon reading the following detailed description, when considered in conjunction with the drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  illustrates a network of routers in accordance with the present invention;  
         [0009]      FIG. 2  illustrates in block form major components of routers depicted in  FIG. 1 ;  
         [0010]      FIG. 3  illustrates in block form the organization of an IPv6 packet header with the MT-ID of the present invention included;  
         [0011]      FIG. 4  illustrates the logical sequence of acts executed by an originating router; and  
         [0012]      FIG. 5  illustrates the logical sequence of acts executed by a receiving router.  
     
    
     DETAILED DESCRIPTION  
       [0013]     Direction attention to  FIG. 1 , there is shown network  10  of interconnected routers  12 . While five routers are illustrated, it is to be understood that the number of routers in a network can be much greater, or even smaller, depending on the configuration of network  10 . Routers  12  collectively function to communicate IPv6 packets across network  10  from an originating point  14  to a destination point  16 . It is to be understood that originating point  14  and destination point  16  can be individual devices manipulated by a user, such as conventional computers, portable computers and other wireless communication devices such as cellular telephones. Within network  10 , individual logical topologies  14  exist. Logical topologies  14  are subgroupings of the various routers  12 .  
         [0014]     Directing attention to  FIG. 2 , functional elements of router  12  include communication connection  20 , processor  22 , memory  24 , link state database  26 , and logical topology list  28 . Logical topology list  28  contains the identities of routers that belong to logical topologies as well as MT-IDs associated with the various logical topologies. Other components, commonly found in routers known to those skilled in the art, are included in router  12 , but are not illustrated.  
         [0015]     Routers  12  are configured to handle IPv6 packets modified in accordance with the present invention. Directing attention to  FIG. 3 , the general organization of fields in IPv6 packet header  30  is illustrated. Version 32 specifies the version of the IPv6 protocol being used. Traffic class  34  is an 8-bit field that specifies an Internet traffic priority delivery value. Flow label  36  is a 20 bit field that specifies special router handling from source to destination(s) for a sequence of packets. Payload length  38  is a 16 bit unsigned field that specifies the length of the data in the packet. When cleared to zero, the option is a hop-by-hop Jumbo payload. Next header  40  is an 8-bit field that specifies the next encapsulated protocol. Hop limit  42  is an 8-bit unsigned field that specifies a value that is initially set to the maximum number of hops the packet can make between routers before it is discarded. For each router that forwards the packet, the hop limit is decremented by 1. When the hop limit field reaches zero, the packet is discarded. This replaces the TTL field in the IPv4 header that was originally intended to be used as a time based hop limit. Source address  44  is a 16-byte field that specifies the IPv6 address of the sending node. Likewise, destination address  46  is 16-byte field that specifies the IPv6 address of the destination node.  
         [0016]     The Organizational Unique Identifier (OUI) is found in the first 24 bits of a MAC address for a network-connected device, which indicate the specific vendor for that device. The IEEE assigns OUIs to vendors. (The last 24 bits of the MAC address are the device&#39;s unique serial number, assigned to the device by the manufacturer.) The OUI sometimes is referred to as the Vendor ID.  
         [0017]     Below is an example of an Interface ID that uses the IANA OUI Assignment:  
                           |0                          2|2      3|3      3|4           6|                   |0                          3|4      1|2      9|0           3|               +----------------------------+--------+--------+-------------+               |OUI(“00-00-5E” + u + g)     |  TYPE  |  TSE   |     TSD     |               +----------------------------+--------+--------+-------------+          
 
         [0018]     Bits “c” are the company-specific bits of the OUI, “u” is the universal/local bit, “g” is the individual/group bit and ‘m’ are the extension identifier bits. In an embodiment, the “u” bit is inverted from its normal sense in the IEEE context; therefore u=l indicates global scope and u=0 indicates local scope.  
         [0019]     The OUI field uses the format of IANA&#39;s OUI: 00-00-5E with ‘u’ and ‘g’ bits and three octets in length. The Type field specifies interpretation of type-specific extension field (TSE) and type-specific data (TSD). The type field is one octet in length. The type-specific extension field (TSE) is one octet in length. The type-specific data field is three octets in length.  
         [0020]     The following interpretations are specified based on the value of the TYPE field:  
                                   TYPE   (TSE, TSD) Interpretation                   0x00-0xFD   reserved for future IANA use       0xFE   (TSE, TSD) together contain an embedded IPv4 address       0xFF   TSD is interpreted based on TSE as follows:                  
 
         [0021]    
       
         
               
               
               
             
           
               
                   
                   
               
               
                   
                   
               
               
                   
                 TSE 
                 TSD Interpretation 
               
               
                   
                   
               
             
             
               
                   
                 0x00-0xFD 
                 reserved for future IANA use 
               
               
                   
                 0xFE 
                 TSD contains 24-bit EUI-48 intf identifier 
               
               
                   
                 0xFF 
                 reserved by IEEE/RAC 
               
               
                   
                   
               
             
          
         
       
     
         [0022]     The present invention provides a new TYPE that indicates that destination address  46  carries an embedded MT-ID as shown below:  
                           |0                          2|2      3|3         4|4       6|                   |0                          3|4      1|2         7|8       3|               +----------------------------+--------+-----------+---------+               |OUI(“00-00-5E” + u + g)     |  TYPE  |   MT-ID   |   TSD   |               +----------------------------+--------+-----------+---------+          
 
         [0023]     Type-specific data (TSD) is a random value generated in order to have a unique Interface-ID within the link. Directing attention to  FIGS. 4 and 5 , by using the new TYPE defined above with the MT-ID, the originator of packet  30  can set the MT-ID in packet  30  at act  50 , send packet  30  to router  12 , and all subsequent routers in the communication path receive packet  30  (act  54 ) read this MT-ID (act  56 ) and automatically associate packet  30  with a logical topology by performing a look up of a table in logical topology list  28  in act  58 . Once the topology is identified, router  12  also knows which routers lie in the path to the identified topology, and sends packet  30  to the closest router in the path to the identified topology.  
         [0024]     While the preferred embodiment of the present invention has been described and illustrated in detail, numerous modifications can be made to embodiments of the present invention without departing from the spirit thereof.