DIS: world wide system identifiers
Thu, 3 Nov 94 1:59:00 MET
There are problems about a distributed system:
- we must ensure that object numbering is unique and secure.
This means a large object identifier size (64 to 128 bits typically).
How will that be handled ?
- now, and particularly if objects migrate, how to route efficiently a
message from source to destination object ?
for example, let's assume I was given some old (but valid) object
handle; by the time ellapsed, the corresponding object may be anywhere
in the world (if it still exists !). How will the system locate it ?
Firstly, this should be transparent to the user; this is strictly a
system implementor problem, which should be solved with maximal efficiency.
What I propose is having host-dependent pointers to represent objects.
Local objects (present on the same host) or faithfully represented by these
pointers as usual, while remote objects are represented as a pointer to a
record containing the full system-wide identifier for the object. Exported
objects reciprocally are pointed at by a record containing the corresponding
identifier. The system may also cache some route and migration information
together with object identifiers.
This allows very quick access to local objects, and equally easy (though
slower) access to remote ones.