ORPC_EXTENT is a binary large object (BLOB) of data whose format is identified by a GUID. It is used on DCOM Remote Protocol calls to pass arbitrary out-of-band data that is not part of the explicit method signature. Unless otherwise specified, clients and servers MUST ignore ORPC_EXTENTs whose format they do not recognize.<6>

 typedef struct tagORPC_EXTENT {
   GUID id;
   unsigned long size;
   [size_is((size+7) & ~7)] byte data[];
 } ORPC_EXTENT;

id: This MUST contain a GUID that identifies the format of the opaque data in the data field.

size: This MUST specify the size, in bytes, in the data field excluding any padding bytes that were added to round the array size to a multiple of 8.

data: This MUST contain an array of bytes that form the extent data. The array size MUST be a multiple of 8 for alignment reasons.