Internet-Draft Mike Davison Cisco Systems Oct 15, 1998 ILMI-Based Server Discovery for NHRP Status of this Memo This document is an Internet-Draft. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet- Drafts as reference material or to cite them other than as "work in progress." To learn the current status of any Internet Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet Drafts shadow directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ftp.ietf.org (US East Coast), or 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. Davison Expires April 15, 1999 [Page 1] Internet Draft Oct 15, 1998 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. Davison Expires April 15, 1999 [Page 2] Internet Draft Oct 15, 1998 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. Davison Expires April 15, 1999 [Page 3] Internet Draft Oct 15, 1998 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 = , 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 Davison Expires April 15, 1999 [Page 4] Internet Draft Oct 15, 1998 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," , 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," , 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," , March, 1998. Author's Address Davison Expires April 15, 1999 [Page 5] Internet Draft Oct 15, 1998 Mike Davison Cisco Systems 170 West Tasman Drive San Jose, California 95134 Phone: (408) 526-4000 EMail: mike.davison@cisco.com Davison Expires April 15, 1999 [Page 6]