diff --git a/omci_defs.py b/omci_defs.py
new file mode 100644
index 0000000..7508411
--- /dev/null
+++ b/omci_defs.py
@@ -0,0 +1,100 @@
+#
+# Copyright 2017 the original author or authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+from enum import Enum
+from scapy.fields import PadField
+from scapy.packet import Raw
+
+
+class OmciUninitializedFieldError(Exception): pass
+
+
+class FixedLenField(PadField):
+    """
+    This Pad field limits parsing of its content to its size
+    """
+    def __init__(self, fld, align, padwith='\x00'):
+        super(FixedLenField, self).__init__(fld, align, padwith)
+
+    def getfield(self, pkt, s):
+        remain, val = self._fld.getfield(pkt, s[:self._align])
+        if isinstance(val.payload, Raw) and \
+                not val.payload.load.replace(self._padwith, ''):
+            # raw payload is just padding
+            val.remove_payload()
+        return remain + s[self._align:], val
+
+
+def bitpos_from_mask(mask, lsb_pos=0, increment=1):
+    """
+    Turn a decimal value (bitmask) into a list of indices where each
+    index value corresponds to the bit position of a bit that was set (1)
+    in the mask. What numbers are assigned to the bit positions is controlled
+    by lsb_pos and increment, as explained below.
+    :param mask: a decimal value used as a bit mask
+    :param lsb_pos: The decimal value associated with the LSB bit
+    :param increment: If this is +i, then the bit next to LSB will take
+    the decimal value of lsb_pos + i.
+    :return: List of bit positions where the bit was set in mask
+    """
+    out = []
+    while mask:
+        if mask & 0x01:
+            out.append(lsb_pos)
+        lsb_pos += increment
+        mask >>= 1
+    return sorted(out)
+
+
+class AttributeAccess(Enum):
+    Readable = 1
+    R = 1
+    Writable = 2
+    W = 2
+    SetByCreate = 3
+    SBC = 3
+
+
+OmciNullPointer = 0xffff
+
+
+class EntityOperations(Enum):
+    # keep these numbers match msg_type field per OMCI spec
+    Create = 4
+    CreateComplete = 5
+    Delete = 6
+    Set = 8
+    Get = 9
+    GetComplete = 10
+    GetAllAlarms = 11
+    GetAllAlarmsNext = 12
+    MibUpload = 13
+    MibUploadNext = 14
+    MibReset = 15
+    AlarmNotification = 16
+    AttributeValueChange = 17
+    Test = 18
+    StartSoftwareDownload = 19
+    DownlaodSection = 20
+    EndSoftwareDownload = 21
+    ActivateSoftware = 22
+    CommitSoftware = 23
+    SynchronizeTime = 24
+    Reboot = 25
+    GetNext = 26
+    TestResult = 27
+    GetCurrentData = 28
+
+