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NAME    [Toc]    [Back]

       nr  -  Redundant  Array  of  Independent  Network Adapters

DESCRIPTION    [Toc]    [Back]

       The NetRAIN virtual interface configures  multiple  interfaces
  on  the  same  LAN segment into a single interface.
       One of the real interfaces is always active while the others
  remain  idle.  If the active interface fails, an idle
       interface comes online.  The failover time  is  adjustable
       depending on your network configuration and operation.

       You  can configure the NetRAIN interface with the ifconfig
       command or with the ioctl system  call.   See  ifconfig(8)
       for  more  information.   You can also adjust some NetRAIN
       default parameters with the sysconfig command.  The SIOCIFADD
 ioctl parameter creates the NetRAIN virtual interface
       and adds the real interfaces to this NetRAIN  set.   After
       creating  the  NetRAIN virtual interface, one or more real
       interfaces are attached to it.  NetRAIN uses  the  Network
       Interface  Failure Finder (NIFF) traffic monitoring facility
 to monitor the interfaces.  See  nifftmt(7)  for  more

       You  can add or remove individual interfaces from the set,
       or disassemble the entire set by using the  ifconfig  command.

   Parameters    [Toc]    [Back]
       The  following list of ioctl parameters is used to configure
 the nr interface: Creates the NetRAIN  virtual  interface
  if  it has not already been created.  This parameter
       requires an  if_nrset  structure  for  the  arg  parameter
       (found  in  the  <net/if.h> file).  The if_nrset structure
       contains the name of the nr interface (nr0, nr1, ...)  and
       a  list  of interfaces to attach to the NetRAIN set.  Upon
       successful completion of this command, the NetRAIN set  is
       configured  and the monitoring thread is activated. If the
       command fails, the name of the interface that could not be
       added is copied back into the user space buffer (for error
       message generation).

              The list of NetRAIN interfaces is kept in a  static
              table.   The  default  size  is  specified  by  the
              nr_maxdev kernel attribute.  The  interfaces  themselves
  are  numbered  from  0  to nr_maxdev-1 (for
              example, nr0, nr1, ...).  To  change  the  size  of
              this  table, change the nr_maxdev attribute for the
              netrain kernel subsystem  by  using  the  sysconfig
              command.   You  must  reboot the system for the new
              value to take effect.  Removes one or  all  members
              of the NetRAIN set.  This command requires an ifreq
              structure  with  the  ifr_name  field  set  to  the
              NetRAIN  interface  name  (nrx)  and  the ifr_index
              field set to the interface index of  the  interface
              to  be removed from the set (the ifreq structure is
              found in the <net/if.h> file).

              You can find the interface index of an interface by
              using  the  SIOCGIFINDEX  ioctl.   If the specified
              interface is the current active  interface  in  the
              NetRAIN  set,  the  active interface is switched to
              another NetRAIN set member.  If the NetRAIN set has
              only  one member, removal of this member is equivalent
 to disassembling the NetRAIN set.

              If the ifr_index field is set to 0, the NetRAIN set
              is disassembled, the UP flag is cleared on all members,
 the hardware address is reset to the  default
              value,  and the hardware address is cleared for the
              nr interface.  You can reuse the nr interface in  a
              future  SIOCIFADD  command.  Forces a manual switch
              to another interface in the NetRAIN set. This  command
  requires an ifreq structure passed in the arg
              field (<net/if.h>). The ifr_name field can  be  the
              nr  interface name or the name of any member in the
              set. If the name is the nr interface or the  active
              member,  the  next  member  in  the  set is brought
              online. If any other member  is  specified  in  the
              ifr_name  field,  that interface is brought online.
              Retrieves the members of a NetRAIN set.  This  command
 requires an if_nrset structure to be passed in
              the arg field (<net/if.h>).  The nr_name field  may
              be  the nr interface name or the name of any member
              of the set. Upon return, the nr_name field contains
              the  nr  interface  name  and the nr_buf field is a
              list of member names. This  buffer  must  be  large
              enough  to hold all the members or an ENOBUFS error
              is returned.  Forces the active interface to switch
              to  the  next available interface at regular intervals.
  It requires an ifreq structure  in  the  arg
              field.  The  ifr_name  field  must  contain  the nr
              interface name and the ifr_value field contains  an
              integer number of seconds between each switch operation.
 A value of zero disables this feature.

       The following ioctl  parameter  is  used  to  control  the
       interface  monitoring  frequency.  This parameter requires
       an mif_t structure (found in  the  <net/if.h>  file).  The
       name  field contains the NetRAIN interface name and the t1
       and t2 fields contain  timer  values.   Sets  two  NetRAIN
       interface timing parameters in the mif_t structure. The t1
       parameter specifies the time period, in seconds, that  the
       traffic  monitor thread delays between reads of the interface
 counters when the network is  running  normally.   If
       there  is no change in the received byte count for t1 seconds,
 the traffic monitor thread issues  a  yellow  alert.
       The recommended t1 value is 4.

              The  t2  parameter  specifies the traffic-free time
              period, in seconds, that must pass before the traffic
  monitor  thread  declares  the interface dead.
              The recommended t2 value is 10 for Ethernet  interfaces
  and  16 for Asynchronous Transfer Mode (ATM)
              LAN Emulation (LANE) interfaces.

       The NetRAIN virtual interface  supports  all  other  ioctl
       parameters.  The  NetRAIN driver propagates these commands
       to the real device driver where appropriate. See the  reference
 page for each individual driver for more details.

RESTRICTIONS    [Toc]    [Back]

       NetRAIN has the following restrictions: You must construct
       a NetRAIN set out of interfaces that are  currently  idle.
       This  means the interfaces cannot be marked as "up" in the
       Set up Network Interface Card(s) dialog box of the  SysMan
       Menu  and  they cannot have IP addresses assigned to them.
       You must use two or more  of  the  same  type  of  network
       interface (FDDI, ATM LAN Emulation, or Ethernet) dedicated
       to a single LAN segment.  If you  use  Ethernet  adaptors,
       theymust  all  be  of  the same speed.  You cannot run LAT
       over a NetRAIN virtual interface (nr) or any of the interfaces
  that  compose  a  NetRAIN set.  Run separate cables
       from each network interface to the appropriate hub or concentrator
  to  provide  physically redundant paths back to
       the network.  This reduces the chance of  network  failure
       due to cables being accidentally unplugged.  If necessary,
       you can adjust the timeout values to ensure  that  NetRAIN
       will  successfully  detect and respond to network failure.
       You can tune these parameters with the sysconfig  command,
       ifconfig  command,  and the ioctl system call.  See nr(7),
       ifconfig(8),    sysconfig(8),    dxkerneltuner(8),     and
       sys_attrs_netrain(5) for more information.

              By  default,  these parameters are tuned for operation
 over Ethernet, but it  is  possible  that  the
              default  values  and other suggested timeout values
              will not work in your environment. For example,  if
              you  are  connected to a switch, failover time will
              depend on the switch and  its  configuration.   You
              must  use UNI Version 3.1 when running NetRAIN over
              LANE to obtain acceptable failover times with  some
              ATM  switches, including the Gigaswitch. If you use
              UNI Version 3.0, the failover time  might  be  long
              because  the  T309  timer  is  set to 90 seconds by
              default on some switches.  If  the  T309  timer  is
              adjustable  on  your  switch,  you can set the T309
              timer to 10 seconds as in UNI Version 3.1 to try to
              achieve acceptable failover times.

ERRORS    [Toc]    [Back]

       A  specified  interface  is  already configured.  Possible
       reasons include: The interface list contained  an  invalid
       interface  type.   All  interfaces  must be either FDDI or
       Ethernet.  The interface list contained interfaces of different
  types.   Interfaces must be either all FDDI or all
       Ethernet.  NetRAIN could not allocate  system  memory  for
       the request.  Possible reasons include: The NetRAIN interface
 name was invalid or the unit number was out of  range
       (0  to  nr_maxdev-1).   An  interface  that was previously
       specified already belongs to a NetRAIN set.

EXAMPLE    [Toc]    [Back]

       The following example creates a NetRAIN set from the specified
  interfaces.  The first argument is the NetRAIN virtual
 interface name, nrx.  The second argument is a commaseparated
  list  of  real interfaces that are added to the
       NetRAIN set.

       #include          <stdio.h>   #include           <errno.h>
       #include                  <sys/socket.h>          #include
       <sys/ioctl.h> #include        <net/if.h>

       #define IFNAMSZ 16

       int main(int argc, char *argv[]) {
           struct if_nrset ifnrset;
           char *addr;
           nrset_t *buf;
           int sock,i;

           if (argc <= 2) {
               printf("Usage: add <nrdev> <dev1>[,dev2...]0);
           /* Load the NetRAIN interface name */
           if (--argc > 0) {
           /* Count the members to be included in the NetRAIN set
           if (--argc > 0) {
               addr = *argv;
               ifnrset.nr_cnt = 1;
               for (i = 0; addr[i] != ' '; i++) {
                   if (addr[i] == ',') {
                       addr[i] = ' ';
               /*  Allocate  a  buffer  large  enough to hold the
       interface names */
              buf = (nrset_t *)malloc(ifnrset.nr_cnt * IFNAMSZ);
               if (buf == NULL) {
                   perror("malloc: ");
               /* Load the interface array */
               for (i=0; i<ifnrset.nr_cnt; i++) {
                   addr += strlen(addr)+1;
               ifnrset.nr_len = ifnrset.nr_cnt * IFNAMSIZ;
               ifnrset.nr_buf = (nrset_t *)buf;

               sock = socket(AF_INET, SOCK_DGRAM, 0);
               if (sock < 0) {
                   perror("socket: ");
               if (ioctl(sock, SIOCIFADD, (char *)&ifnrset) != 0)
                   perror("SIOCIFADD: ");

           return(0); }

SEE ALSO    [Toc]    [Back]

       Functions: ioctl(2)

       Interfaces: alt(7), bcm(7), ee(7), faa(7), fta(7), fza(7),
       le(7), ln(7), tu(7)

       Commands: nifftmt(7), ifconfig(8), sysconfig(8)

       Tuning: sys_attrs_netrain(5)

       Network Administration: Connections

       System Configuration and Tuning

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