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Versions: 00 01 02 04 05 rfc2603                                        
Internet-Draft                                           Mike Davison
                                                         Cisco Systems
                                                         Oct 15, 1998



                  ILMI-Based Server Discovery for NHRP
                  <draft-ietf-ion-discov-nhrp-02.txt>




Status of this Memo

   This document is an Internet-Draft.  Internet-Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
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   ftp.isi.edu (US West Coast).

   This memo provides information for the Internet community. This memo
   does not specify an Internet standard of any kind.  Distribution of
   this memo is unlimited.


Abstract


   This memo defines how ILMI-based Server Discovery, which provides a
   method for ATM-attached hosts and routers to dynamically determine
   the ATM address of servers,  shall be used to locate NHRP servers.










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1. Introduction


   Presently, configuring a host or router to use NHRP [1] is cumbersome
   and error-prone since it requires at least one ATM addresses to be
   statically configured on each host or router in the network.
   Further, it is impossible to implement a diskless host to use NHRP
   since local configuration is required.  ILMI-based Server Discovery,
   hereafter referred to as "server discovery," provides a solution to
   these problems.

   A brief overview of the Service Registry MIB, as defined by the ATM
   Forum, is provided in this memo. The reader should consult [2] for a
   complete description of this MIB, but the information contained here
   is sufficient for an understanding of its use to support NHRP server
   discovery.


2. ILMI 4.0 Service Registry MIB


   Server discovery utilizes the Service Registry MIB defined by the ATM
   Forum in ILMI Specification Version 4.0 [2]. To support the existing
   framework for IP over ATM, ATM switches must support the Service
   Registry MIB.

   A row in the service registry table [2] is defined as:

      AtmfSrvcRegEntry ::= SEQUENCE {
          atmfSrvcRegPort          INTEGER,
          atmfSrvcRegServiceID     OBJECT IDENTIFIER,
          atmfSrvcRegATMAddress    AtmAddress,
          atmfSrvcRegAddressIndex  INTEGER,
          atmfSrvcRegParm1         OCTET STRING
      }

   The definition of each field in this structure is:

      atmfSrvcRegPort - The port number for which this entry contains
          management information. The value of zero may be used to
          indicate the ATM interface over which a management request
          was received.

      atmfSrvcRegServiceID - This is the service identifier which
          uniquely identifies the type of service at the address
          provided in the table. (See Appendix for NHRP OID.)

      atmfSrvcRegATMAddress - This is the full address of the service.



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          The ATM client will use this address to establish a connection
          with the service.

      atmfSrvcRegAddressIndex - An arbitrary integer to differentiate
          multiple rows containing different ATM addresses for the same
          service on the same port.

      atmfSrvcRegParm1 - An octet string whose size and meaning is
          determined by the value of atmfSrvcRegServiceID.

   The service registry table is indexed by atmfSrvcRegPort,
   atmfSrvcRegServiceID and atmfSrvcRegAddressIndex.


2.1 Service Parameter String


   A generic parameter string is defined in the service registry table,
   thus allowing protocol-specific parameters to be specified. To be
   consistent with [1], the parameter string for NHRP shall be:

       mar$pro.type   16 bits     Protocol type
       mar$pro.snap   40 bits     Optional extension to protocol type
       mar$plen        8 bits     Length of protocol address (a)
       mar$addr        a octets   Network address
       mar$mask        a octets   Network mask

   Where

       mar$pro.type   - See [1]. (IPv4 is 0x0800, IPv6 is 0x86DD)
       mar$pro.snap   - See [1]. (IPv4 and IPv6 are 0)

       mar$plen       - Length of the protocol address.
                        (IPv4 is 4, IPv6 is 16)

       mar$addr       - Network address represented in network byte
                        order

       mar$mask       - Network mask represented in network byte order


2.2 Service Object Identifier



   This OID, assigned in the ATM Forum Service Registry MIB, names
   ATMARP within the context of server discovery.




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     atmfSrvcRegNHRP OBJECT IDENTIFIER ::= { 1.3.6.1.4.1.353.1.5.5 }

   It does not name any managed objects, rather is used to locate
   appropriate rows in the service registery table.


3. Next Hop Client Behavior


   An Next Hop Client NHC) will access the service registry table via
   ILMI using the SNMP GetNext operator to "sweep" (SNMP parlance for a
   linear search) beginning with {Port = 0, ServiceID = <see Appendix>,
   Index = 0} while holding the port number and the serviceID constant.
   (Port number 0 is used within ILMI to indicate "this port.")

   An NHC with no local configuration, such as a diskless workstation,
   must use the row with the lowest index value if multiple Next Hop
   Server (NHS), possibly for multiple networks, are listed.

   NHC that have local IP configuration must use a row that has the
   appropriate IP address.  For example, consider the case where an IP
   router has 3 logical interfaces defined on a single physical
   interface with IP addresses 1.0.0.1/8, 128.10.0.1/16 and
   171.69.150.226/24. The router will sweep the service registry table
   looking for a rows that have atmfSrvcRegParm1 values as shown below:

     Net number/mask  atmfSrvcRegParm1
     ---------------- --------------------------------------------------
     1.0.0.0/8        08 00 00 00 00 00 00  04  01 00 00 00  ff 00 00 00
     128.10.0.0/16    08 00 00 00 00 00 00  04  80 0a 00 00  ff ff 00 00
     171.69.150.0/24  08 00 00 00 00 00 00  04  ab 45 96 00  ff ff ff 00

   When the correct atmfSrvcRegParm1 values are located, the router may
   then establish an SVC to the selected NHS and perform the appropriate
   protocol operations.

   Redundant NHS are supported with multiple rows in the service
   registry table. This list of NHS is ordered with the primary NHS
   having the lowest index value. The NHC must attempt to utilize the
   primary NHS before utilizing a secondary NHS. Administrators must
   ensure that the listed NHS are synchronized via [3].


4. NHRP Server (NHS) Behavior


   A Next Hop Server (NHS) shall be locally configured. The NHS may
   retrieve the NHRP service registry data to validate the results. If



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   an incorrect row is retrieved the error may be flagged in a locally
   significant way.


5. Relationship with PNNI Augmented Routing


   An augmented version PNNI ("PNNI Augmented Routing," or PAR) [4] is
   being developed by the ATM Forum. PAR can distribute data such as NHS
   addresses. Further, the ATM Forum is developing a proxy mechanism for
   PAR (Proxy PAR) [5] that would allow a UNI-attached host or router to
   access PAR data without a full PAR implementation.

   These mechanisms offer a promising way to manage the service registry
   tables maintained on each switch in an ATM network, yet would not
   require changes to the mechanism defined in this memo. Hosts and
   routers can continue to utilize ILMI-based or Proxy PAR-based server
   discovery and network administrators could manage the service
   registry data with local configuration or via PAR and Proxy PAR.


6. Security Considerations


   The server discovery mechanism is intended for environments where a
   given ATM switch and its attached hosts or routers are in the same
   administrative domain, hence no authentication is required.


References

      [1]  Luciani, J., et al., "NBMA Next Hop Resolution Protocol,"
      <draft-ietf-rolc-nhrp-11.txt>, March, 1997.

      [2]  ATM Forum, "Integrated Local Management Interface (ILMI)
      Specification Version 4.0," af-ilmi-0065.000, September, 1996.

      [3]  Luciani, J., and Fox, B., "A distributed NHRP Service Using
      SCSP," <draft-ietf-ion-scsp-atmarp-00.txt>, April, 1997.

      [4]  Callon, R., et al., "An Overview of PNNI Augmented Routing,"
      ATM-Forum 96-0354, April, 1996.

      [5]  Droz, P., Przygienda, T., "Proxy PAR,"
      <draft-ietf-ion-proxypar-arch-00.txt>, March, 1998.


Author's  Address



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      Mike Davison
      Cisco Systems
      170 West Tasman Drive
      San Jose, California 95134

      Phone: (408) 526-4000
      EMail: mike.davison@cisco.com












































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