Delivery
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... number of commercial implementations of distributed databases which
utilize - and thus are penalized by - an ordered delivery service.
...
...
This RFC proceeds as follows. The principles of partial order
delivery, published in [ACCD93a], are presented in Section 2. The
notion of partial reliability ...
... Partial Order Delivery ...
... delivered in either order, there is no need to use an ordered service
that must delay delivery of the second one transmitted until the
first arrives as the following examples demonstrate.
...
... valid simply by omitting the "order by" clause. Here any of 4! = 24
delivery orderings would satisfy the application, or from the
transport layer's point of view, all records are immediately
...
... valid orderings) |
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Figure 1: Ordered vs. Partial Ordered vs. Unordered Delivery
It is vital for the transport layer ...
... have temporal value that lasts for an entire established connection
and require reliable delivery (NL = No Loss allowed). An example of
BART-NL objects would be the database records in Example 2.1 or the
...
... type BART-NL, the service is reliable. One possible way to assure
eventual delivery of a BART-NL object in a protocol is for the sender
to buffer ...
... retransmission, but not everlasting. Once the temporal value of
these objects has expired, it is better to presume them lost than to
delay further the delivery pipeline of information. One possibility
for deciding when an object's usefulness has expired is to require
each object to contain information defining its precise temporal
...
... and the application is able to process the fragments (this notion of
fragmented delivery is discussed further in Section 6).
...
... connection, the communicating TCPs
each have their respective jobs to perform to ensure proper data
delivery. The sending TCP ascertains the object ordering and
reliability ...
... remove the constraint of any object whose
delivery depends on object 5 by clearing all entries of row 5. This
may enable other objects to be delivered (for example, if object 2 is
...
... row 5. This
may enable other objects to be delivered (for example, if object 2 is
buffered then the delivery of object 1 will make object 2
deliverable). This leads us to the next issue - delivery of stored
...
... buffered then the delivery of object 1 will make object 2
deliverable). This leads us to the next issue - delivery of stored
objects.
...
...
Buffered Set: objects stored in a buffer awaiting delivery.
Bufferable Set: objects which can be stored but not immediately
...
...
While ordered, reliable delivery is ideal, the existence of less-
than-ideal underlying networks can cause delays for applications that
...
... when needed.
In another area, the notion of fragmented delivery, mentioned in the
beginning of Section 4, looks like a promising technique for certain
classes ...
... classes of applications which may offer a substantial improvement in
memory utilization. Briefly, the term fragmented delivery refers to
the ability to transfer less-than-complete objects between the
transport layer ...
... The notion of a partial ordering extends QOS flexibility to include
object delivery, reliability, and temporal value thus allowing the
transport layer ...
...
(1) Replacing the requirement for ordered delivery with one for
application-dependent partial ordering
...
... Hardt-Kornacki, S., and L. Ness, "Optimization Model for the Delivery of Interactive Multimedia Documents", In Proc. Globecom '91, 669-673, Phoenix, Arizona, December 1991. ...