# ibacm

## NAME



           ibacm - address and route resolution services for InfiniBand.
    


## SYNOPSIS



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


## DESCRIPTION



           The IB ACM implements and provides a framework for name, address,
           and route (path) resolution 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 service 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
           benefit, 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, efficient, and
           extensible.  It implements a plugin architecture that allows a
           vendor to supply its proprietary provider in addition to the
           default provider.  The current default provider implementation
           ibacmp limits network traffic, SA interactions, and centralized
           services.  Ibacmp supports multiple resolution protocols in order
           to handle different fabric topologies.
    
           The IB ACM package is comprised of three components: the ibacm
           core service, the default provider ibacmp shared library, and a
           test/configuration utility - ib_acme.  All three are userspace
           components and are available for Linux.  Additional details are
           given below.
    


## OPTIONS



           -D     run in daemon mode (default)
    
           -P     run as standard process
    
           -A addr_file
                  address configuration file
    
           -O option_file
                  option configuration file
    
           --systemd
                  Enable systemd integration. This includes optional socket
                  activation of the daemon's listening socket.
    


## QUICK START GUIDE



           1. Prerequisites: libibverbs and libibumad must be installed.  The
           IB stack should be running with IPoIB configured.  These steps
           assume that the user has administrative privileges.
    
           2. Install the IB ACM package.  This installs ibacm, ibacmp,
           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.
           Similarly, the command ib_acme -e could be used to enumerate all
           endpoints created by the local ibacm service.
    


## NOTES



           ib_acme:
    
           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 configuration.
           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 to
           the IB endpoints.  IP addresses, on the other hand, are assigned
           dynamically.  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 core service and default provider, 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 values.
    
           ibacm:
    
           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 providers can be
           loaded by the core service, depending on the configuration.  In
           the default provider ibacmp, one or more back-end protocols are
           used to satisfy user requests.  Although ibacmp 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 default provider ibacmp implements an ARP like
           protocol and either uses IB multicast records to construct path
           record data or queries the SA directly, depending on the selected
           route protocol.  By default, the ibacmp provider uses and caches
           SA path record queries.
    
           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 ibacmp
           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 the destination name/address is not cached locally
           in the default provider, it sends a multicast request out on the
           lowest priority multicast group on the local endpoint.  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 provider ibacmp has several
           additional restrictions:
    
           - The ibacmp is limited in its handling of dynamic changes.  ibacm
           must be stopped and restarted if a cluster is reconfigured.
    
           - Support for IPv6 has not been verified.
    
           - The number of multicast groups that an endpoint can support is
           limited to 2.
    
           The ibacmp contains several internal caches.  These include caches
           for GID and LID destination 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.
    


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