Open Fabrics Enterprise Distribution (OFED)
		    RDMA CM in OFED 1.2 Release Notes
			  
			   May 2007


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Table of Contents
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1. Overview
2. New Features
3. Known Issues

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1. Overview
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The RDMA CM is a communication manager used to setup reliable, connected

and unreliable datagram data transfers.  It provides an RDMA transport

neutral interface for establishing connections.  The API is based on sockets,

but adapted for queue pair (QP) based semantics: communication must be

over a specific RDMA device, and data transfers are message based.


The RDMA CM only provides the communication management (connection setup /

teardown) portion of an RDMA API.  It works in conjunction with the verbs

API for data transfers.

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2. New Features
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The RDMA CM now supports connected, datagram, and multicast data transfers.

When used over Infiniband, the RDMA CM will make use of a local path record
cache, if it is enabled.  On large fabrics, use of the local cache can greatly
reduce connection time.  Use of a cache is not necessary for iWarp.

Man pages have been created to describe the various interfaces and test
programs available.  For a full list, users should refer to the rdma_cm.7 man
page.

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3. Known Issues
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The RDMA CM relies on the operating system's network configuration tables to
map IP addresses to RDMA devices.  Incorrectly configured network
configurations can result in the RDMA CM being unable to locate the correct
RDMA device.  Currently, the RDMA CM only supports IPv4 addressing.

All RDMA interfaces must provide a way to map IP addresses to an RDMA device.
For Infiniband, this is done using IPoIB, and requires correctly configured
IPoIB device interfaces sharing the same multicast domain.  For details on
configuring IPoIB, refer to ipoib_release_notes.txt.  For RDMA devices to
communicate, they must support the same underlying network and data link
layers.

If you experience problems using the RDMA CM, you may want to check the
following:

   * Verify that you have IP connectivity over the RDMA devices.  For example,
     ping between iWarp or IPoIB devices.

   * Ensure that IP network addresses assigned to RDMA devices do not
     overlap with IP network addresses assigned to standard Ethernet devices.

   * For multicast issues, either bind directly to a specific RDMA device, or
     configure the IP routing tables to route multicast traffic over an RDMA
     device's IP address.