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Configuring Inverse Multiplexing for ATM (IMA)

Inverse multiplexing for ATM (IMA) is a standardized technology used to transport ATM traffic over a bundle of T1 or E1 interfaces, also known as an IMA Group, allowing for an increase in the bandwidth capacity. When you configure IMA on ACX Series routers, you must configure the following:

  • The aggregated device count—The device count is the number of IMA group interfaces created on the CT1 or CE1 interfaces. The logical ATM interface that is part of the IMA group has the following naming format: at-fpc/pic/port with the port number taken from the last port on the MIC plus 1. For example, on the ACX2000 router with a 16-port built-in T1/E1 TDM MIC, the IMA group interface numbering starts with at-0/0/16 and increments by 1 to at-0/0/17, and so on. On the ACX1000 router with an 8-port built-in T1/E1 TDM MIC, the IMA group interface numbering starts with at-0/0/8 and increments by 1 to at-0/0/9, and so on
  • The framing mode—Emulation is a mechanism that duplicates the essential attributes of a service, such as T1 or E1, over a packet-switched network. The built-in channelized T1 and E1 interfaces (CT1 and CE1) on the ACX Series routers can be configured to work in either T1 or E1 mode, and these child T1 and E1 interfaces can be configured to carry ATM services over the packet-switched network.
  • One full T1 or E1 interface on the channelized CT1 or CE1 interface—The built-in channelized interface is a non-configurable interface that requires a child T1 or E1 or ATM interface on which you configure the parameters.
  • The T1 or E1 interface as a member of the IMA group of the respective IMA link—Each child T1 or E1 interface of a channelized CT1 or CE1 interface is the physical interface over which the ATM signals are carried. This T1 or E1 interface must be specified as a member of an IMA group so that the IMA link will work.
  • IMA group interface configuration—Each IMA group interface (at-fpc/pic/port) must be configured with all ATM properties for it to work properly: logical link-layer encapsulation type, the circuit cross-connect protocol suite, and the entire ATM device must be dedicated to the ATM cell relay circuit.

Configure IMA on built-in channelized T1 and E1 interfaces:

  1. Configure the framing mode:

    [edit chassis fpc fpc-slot pic pic-slot]
    user@host# set framing (t1 | e1)

    For example, to set E1 framing:

    [edit chassis fpc 0 pic 0
    user@host# set framing e1

    This configuration is for E1 framing, which results in the PIC running at the E1 interface speed. To configure T1 framing, use the t1 option. The following output shows this configuration:

    [edit]
user@host# show chassis 
fpc 0 {
    pic 0 {
        framing e1;
    }
}

    The following output shows eight CE1 interfaces created on an ACX1000 router:

    user@host# run show interfaces terse 
Interface               Admin Link Proto    Local                 Remote
ce1-0/0/0               up    up  
ce1-0/0/1               up    up  
ce1-0/0/2               up    up  
ce1-0/0/3               up    up  
ce1-0/0/4               up    up  
ce1-0/0/5               up    up  
ce1-0/0/6               up    up  
ce1-0/0/7               up    up

    After a PIC is brought online and depending on the framing option used (t1 or e1), on the ACX2000 router, 16 CT1 or 16 CE1 interfaces are created; on the ACX1000 router, 8 CT1 or 8 CE1 interfaces are created.

  2. Configure the aggregated device count:

    [edit chassis fpc fpc-slot pic pic-slot]
    user@host# set aggregated-devices ima device-count number

    For example:

    [edit chassis fpc 0 pic 0
    user@host# set aggregated-devices ima device-count 2

    This configuration creates two IMA group interfaces on the Routing Engine. The following output shows this configuration:

    [edit]
user@host# show chassis 
fpc 0 {
    pic 0 {
        aggregated-devices {
            ima {
                device-count 2;
            }
        }
    }
}

    The following output shows the two IMA group interfaces created on an ACX1000 router with eight built-in channelized interfaces so the IMA group interface naming starts with port 8, at-0/0/8 and increments by one to at-0/0/9:

    user@host> show interfaces terse
Interface               Admin Link Proto    Local                 Remote
ce1-0/0/0               up    up  
e1-0/0/0                up    up  
ce1-0/0/1               up    up  
e1-0/0/1                up    up  
ce1-0/0/2               up    up  
ce1-0/0/3               up    up  
ce1-0/0/4               up    up  
ce1-0/0/5               up    up  
ce1-0/0/6               up    up  
ce1-0/0/7               up    up  
at-0/0/8                up    up  
at-0/0/9                up    up

    Note: When you change the aggregated device count, all interfaces on the MIC are restarted.

  3. Configure at least one full T1 or E1 interface on the channelized CE1 or CT1 interface:

    [edit interfaces (ct1 | ce1)-fpc/pic /port]
    user@host# set no-partition interface-type e1

    In this example, you configure two full E1 interfaces because you have two IMA groups configured in the previous step:

    [edit interfaces ce1-0/0/0
    user@host# set no-partition interface-type e1

    [edit interfaces ce1-0/0/1
    user@host# set no-partition interface-type e1

    The following output shows this configuration. Notice that on each ce1 interface, a corresponding e1 interface is created with the same fpc/pic/port parameters as its parent ce1 interface:

    [edit]
user@host# show interfaces
ce1-0/0/0 {
    no-partition interface-type e1;
}
e1-0/0/0 {
}
ce1-0/0/1 {
    no-partition interface-type e1;
}
e1-0/0/1 {
}

    user@host> show interfaces terse
Interface               Admin Link Proto    Local                 Remote
ce1-0/0/0               up    up  
e1-0/0/0                up    up  
ce1-0/0/1               up    up  
e1-0/0/1                up    up  
ce1-0/0/2               up    up  
ce1-0/0/3               up    up  
ce1-0/0/4               up    up  
ce1-0/0/5               up    up  
ce1-0/0/6               up    up  
ce1-0/0/7               up    up  
at-0/0/8                up    up  
at-0/0/9                up    up
  4. Specify the T1 or E1 interface as a member of the IMA group of the respective IMA link (at-0/0/8 or at-0/0/9):

    [edit interfaces (e1 | t1)-fpc/pic /port]
    user@host# set ima-link-options group-id group-id

    In this example, you configure IMA encapsulation on two E1 interfaces because you have set up two IMA groups in Step 3.

    [edit interfaces e1-0/0/0
    user@host# set ima-link-options group-id 8

    [edit interfaces e1-0/0/1
    user@host# set ima-link-options group-id 9

    The following output shows this configuration:

    [edit]
user@host# show interfaces 
e1-0/0/0 {
    ima-link-options group-id 8;
    encapsulation ima;
}
e1-0/0/1 {
    ima-link-options group-id 9;
    encapsulation ima;
}
  5. For each IMA group interface, configure a logical link-layer encapsulation type (encapsulation atm-ccc-cell-relay) and the circuit cross-connect protocol suite (family ccc), then dedicate the entire ATM device to the ATM cell relay circuit (allow-any-vci):

    [edit interfaces at-fpc/pic /port unit logical-unit-number]
    user@host# encapsulation atm-ccc-cell-relay
    user@host# family ccc
    user@host# allow-any-vci

    In this example, you configure these statements on the two IMA group interfaces at-0/0/8 and at-0/0/9.

    [edit]
user@host# show interfaces
at-0/0/8 {
    unit 0 {
        encapsulation atm-ccc-cell-relay;
        allow-any-vci;
        family ccc;
    }
}
at-0/0/9 {
    unit 0 {
        encapsulation atm-ccc-cell-relay;
        allow-any-vci;
        family ccc;
    }
}
  6. Verify that the interfaces are up:

    The following output shows the channelized CE1 interface:

    user@host> show interfaces ce1-0/0/0 
Physical interface: ce1-0/0/0, Enabled, Physical link is Up
  Interface index: 128, SNMP ifIndex: 530
  Link-level type: Controller, Clocking: Internal, Speed: E1, Loopback: None, Framing: G704,
  Parent: None
  Device flags   : Present Running
  Interface flags: Point-To-Point SNMP-Traps Internal: 0x0
  Link flags     : None
  CoS queues     : 8 supported, 4 maximum usable queues
  Last flapped   : 2012-04-07 13:42:45 PDT (01:52:59 ago)
  DS1   alarms   : None
  DS1   defects  : None
    Line encoding: HDB3

    The following output shows the child E1 interfaces:

    user@host> show interfaces e1-0/0/0 
Physical interface: e1-0/0/0, Enabled, Physical link is Up
  Interface index: 152, SNMP ifIndex: 559
  Link-level type: IMA-Link, MTU: 1504, Speed: E1, Loopback: None, FCS: 16,
  Parent: ce1-0/0/0 Interface index 128
  Device flags   : Present Running
  Interface flags: Point-To-Point SNMP-Traps Internal: 0x0
  Link flags     : None
  CoS queues     : 8 supported, 4 maximum usable queues
  Last flapped   : 2012-04-07 15:34:15 PDT (00:01:49 ago)
  Input rate     : 0 bps (0 pps)
  Output rate    : 0 bps (0 pps)
  IMA Link alarms   : None
  IMA Link defects  : None
  IMA Link state    : Line: OK, NE-Rx: Active, NE-Tx: Active, FE-Rx: Active, FE-Tx: Active
  DS1   alarms   : None
  DS1   defects  : None
    user@host> show interfaces e1-0/0/1  
Physical interface: e1-0/0/1, Enabled, Physical link is Up
  Interface index: 153, SNMP ifIndex: 561
  Link-level type: IMA-Link, MTU: 1504, Speed: E1, Loopback: None, FCS: 16,
  Parent: ce1-0/0/1 Interface index 130
  Device flags   : Present Running
  Interface flags: Point-To-Point SNMP-Traps Internal: 0x0
  Link flags     : None
  CoS queues     : 8 supported, 4 maximum usable queues
  Last flapped   : 2012-04-07 16:19:25 PDT (00:04:48 ago)
  Input rate     : 0 bps (0 pps)
  Output rate    : 0 bps (0 pps)
  IMA Link alarms   : None
  IMA Link defects  : None
  IMA Link state    : Line: OK, NE-Rx: Active, NE-Tx: Active, FE-Rx: Active, FE-Tx: Active
  DS1   alarms   : None
  DS1   defects  : None

    The following output shows the IMA group interfaces:

    user@host> show interfaces at-0/0/8 
Physical interface: at-0/0/8, Enabled, Physical link is Up
  Interface index: 138, SNMP ifIndex: 568
  Link-level type: ATM-PVC, MTU: 2048, Speed: Unspecified, Loopback: None,
  Payload scrambler: Enabled
  Device flags   : Present Running
  Link flags     : None
  CoS queues     : 8 supported, 4 maximum usable queues
  Current address: 84:18:88:c0:5a:08
  Last flapped   : 2012-04-07 15:34:15 PDT (00:02:10 ago)
  Input rate     : 0 bps (0 pps)
  Output rate    : 0 bps (0 pps)
  IMA Group alarms   : None
  IMA Group defects  : None
  IMA Group state    : NE: Operational, FE: Operational
    [edit]
user@host> show interfaces at-0/0/9 
Physical interface: at-0/0/9, Enabled, Physical link is Up
  Interface index: 139, SNMP ifIndex: 569
  Link-level type: ATM-PVC, MTU: 2048, Speed: Unspecified, Loopback: None, Payload scrambler: Enabled
  Device flags   : Present Running
  Link flags     : None
  CoS queues     : 8 supported, 4 maximum usable queues
  Current address: 84:18:88:c0:5a:09
  Last flapped   : 2012-04-04 21:16:08 PDT (15:25:39 ago)
  Input rate     : 0 bps (0 pps)
  Output rate    : 0 bps (0 pps)
  IMA Group alarms   : None
  IMA Group defects  : None
  IMA Group state    : NE: Operational, FE: Operational
 

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Published: 2013-07-23

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