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ibacm(1)				      ibacm					 ibacm(1)

       ibacm - address and route resolution services for InfiniBand.

       ibacm [-D] [-P] [-A addr_file] [-O option_file]

       The IB ACM implements and provides a framework for name, address, and route (path) resolu-
       tion services over InfiniBand.  It is intended to  address  connection  setup  scalability
       issues running MPI applications on large clusters.  The IB ACM provides information needed
       to establish a connection, but does not implement the CM protocol.

       A primary user of the ibacm service is the librdmacm library.  This  enables  applications
       to make use of the ibacm service without code changes or needing to be aware that the ser-
       vice is in use.	librdmacm versions 1.0.12 - 1.0.15 can invoke IB ACM services when  built
       using  the --with-ib_acm option.  Version 1.0.16 and newer of librdmacm will automatically
       use  the  IB  ACM  if  it  is  installed.   The	IB  ACM  services  tie	 in   under   the
       rdma_resolve_addr,  rdma_resolve_route,	and rdma_getaddrinfo routines.	For maximum bene-
       fit, the rdma_getaddrinfo routine should be used,  however  existing  applications  should
       still  see  significant connection scaling benefits using the calls available in librdmacm
       1.0.11 and previous releases.

       The IB ACM is focused on being scalable and efficient.  The current implementation  limits
       network traffic, SA interactions, and centralized services.  ACM supports multiple resolu-
       tion protocols in order to handle different fabric topologies.

       The IB ACM package is comprised of two components: the ibacm service and a test/configura-
       tion  utility  -  ib_acme.   Both are userspace components and are available for Linux and
       Windows.  Additional details are given below.

       -D     run in daemon mode (default)

       -P     run as standard process

       -A addr_file
	      address configuration file

       -O option_file
	      option configuration file

       1. Prerequisites: libibverbs and libibumad must be installed.  The IB stack should be run-
       ning  with  IPoIB  configured.  These steps assume that the user has administrative privi-

       2. Install the IB ACM package.  This installs ibacm, ib_acme, and init.d scripts.

       3. Run 'ibacm' as administrator to start the ibacm daemon.

       4. Optionally, run 'ib_acme -d <dest_ip> -v' to verify that the ibacm service is running.

       5. Install librdmacm, using the build option --with-ib_acm if needed.  This  build  option
       is  not	needed	with librdmacm 1.0.17 or newer.  The librdmacm will automatically use the
       ibacm service.  On failures, the librdmacm will fall back to normal resolution.

       6. You can use ib_acme -P to gather performance statistics from the local ibacm daemon  to
       see if the service is working correctly.


       The  ib_acme program serves a dual role.  It acts as a utility to test ibacm operation and
       help verify if the ibacm service and selected protocol is usable for a given cluster  con-
       figuration.   Additionally, it automatically generates ibacm configuration files to assist
       with or eliminate manual setup.

       ibacm configuration files:

       The ibacm service relies on two configuration files.

       The ibacm_addr.cfg file contains name and address mappings  for	each  IB  <device,  port,
       pkey>  endpoint.   Although  the names in the ibacm_addr.cfg file can be anything, ib_acme
       maps the host name and IP addresses to the IB endpoints.  If the address  file  cannot  be
       found, the ibacm service will attempt to create one using default values.

       The ibacm_opts.cfg file provides a set of configurable options for the ibacm service, such
       as timeout, number of retries, logging level, etc.  ib_acme generates  the  ibacm_opts.cfg
       file  using static information.	If an option file cannot be found, ibacm will use default


       The ibacm service is responsible for resolving names  and  addresses  to  InfiniBand  path
       information and caching such data.  It should execute with administrative privileges.

       The  ibacm  implements  a  client  interface  over TCP sockets, which is abstracted by the
       librdmacm library.  One or more back-end protocols are used by the ibacm service  to  sat-
       isfy  user  requests.   Although the ibacm supports standard SA path record queries on the
       back-end, it also supports a resolution protocol based on multicast traffic.   The  latter
       is  not	usable	on  all fabric topologies, specifically ones that may not have reversible
       paths or fabrics using torus routing.  Users should use the ib_acme utility to verify that
       multicast protocol is usable before running other applications.

       Conceptually,  the ibacm service implements an ARP like protocol and either uses IB multi-
       cast records to construct path record data or queries the SA directly,  depending  on  the
       selected  route	protocol.   By default, the ibacm services uses and caches SA path record

       Specifically, all IB endpoints join a number of multicast groups.  Multicast groups differ
       based  on  rates, mtu, sl, etc., and are prioritized.  All participating endpoints must be
       able to communicate on the lowest priority multicast group.  The ibacm assigns one or more
       names/addresses to each IB endpoint using the ibacm_addr.cfg file.  Clients provide source
       and destination names or addresses as input to the service, and	receive  as  output  path
       record data.

       The  service maps a client's source name/address to a local IB endpoint.  If a client does
       not provide a source address, then the ibacm service will select one based on the destina-
       tion  and local routing tables.	If the destination name/address is not cached locally, it
       sends a multicast request out on the lowest priority multicast group  on  the  local  end-
       point.	The  request  carries  a  list	of multicast groups that the sender can use.  The
       recipient of the request selects the highest priority multicast group that it can  use  as
       well  and  returns that information directly to the sender.  The request data is cached by
       all endpoints that receive the multicast request message.  The source endpoint also caches
       the  response  and  uses the multicast group that was selected to construct or obtain path
       record data, which is returned to the client.

       The current implementation of the IB ACM has several additional restrictions:

       - The ibacm is limited in its handling of dynamic changes.   ibacm  must  be  stopped  and
       restarted if a cluster is reconfigured.

       -  Cached  data	does  not  timed  out  and is only updated if a new resolution request is
       received from a different QPN than a cached request.

       - Support for IPv6 has not been verified.

       - The number of addresses that can be assigned to a single endpoint is limited to 4.

       - The number of multicast groups that an endpoint can support is limited to 2.

       The ibacm contains several internal caches.  These include caches for GID and LID destina-
       tion  addresses.   These  caches  can  be  optionally preloaded. ibacm supports the OpenSM
       dump_pr plugin "full" PathRecord format which is used to preload these caches.	The  file
       format  is specified in the ibacm_opts.cfg file via the route_preload setting which should
       be set to full_opensm_v1 for this file format.  Default format  is  none  which	does  not
       preload	these  caches.	 See  dump_pr.notes.txt  in  dump_pr  for more information on the
       full_opensm_v1 file format and how to configure OpenSM to generate this file.

       Additionally, the  name,  IPv4,	and  IPv6  caches  can	be  be	preloaded  by  using  the
       addr_preload  option.  The default is none which does not preload these caches. To preload
       these caches, set this option to acm_hosts and configure the addr_data_file appropriately.

       ibacm(7), ib_acme(1), rdma_cm(7)

ibacm					    2013-07-18					 ibacm(1)
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