Reliability
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... does not guarantee any ordering such as that provided by UDP. A
similar "all-or-nothing" choice is made for object reliability -
reliable connections which guarantee all objects will be delivered
...
... transport which makes no guarantee. What is
more appropriate for some applications is a partial order and/or
partial reliability service where a subset of objects being
communicated must arrive in the order transmitted, yet some objects
...
... they are ideal candidates for using a partial order, partial
reliability service. In general, any application which communicates
parallel and/or independent data structures ...
... range of discreet values encompassing both of
the extremes and all possible partial orderings in between. A
similar phenomenon is demonstrated in the area of reliability.
It is worth mentioning that a TCP ...
... delivery, published in [ACCD93a], are presented in Section 2. The
notion of partial reliability, published in [ACCD93b], is introduced
in Section 3 followed by an explanation of "reliability ...
... reliability, published in [ACCD93b], is introduced
in Section 3 followed by an explanation of "reliability classes".
Then, the practical issues involved with setting up ...
... reliable and delivers data (records) in an order that conforms to
their SQL request. In reality though, it is the transport layer
protocol which provides the reliability and order on top of an
unreliable network layer ...
... Reliability vs. Order ...
... quality of service
that combines a partial order with a level of tolerated loss (partial
reliability). Traditionally there exist 4 services: reliable-
ordered, reliable-unordered, unreliable-ordered, and unreliable-
...
... | |
|<-- unreliable- |<-- unreliable-
RELIABILITY | ordered | unordered
|<-- |<--
| |
...
... range of discrete possibilities as depicted in Figure 6.
Additionally, as will be discussed presently, the notion of
reliability is extended to allow for varying degrees of reliability
on a per-object basis providing even greater flexibility and improved
...
... Additionally, as will be discussed presently, the notion of
reliability is extended to allow for varying degrees of reliability
on a per-object basis providing even greater flexibility and improved
resource utilization.
...
... . | . . . . . . . . . . . |
| . . . . . . |
RELIABILITY | . . . unreliable-PO . . . |
| . . . . . . . . . . . |
...
... Reliability Classes ...
... When considering unreliable service, one cannot assume that all
objects are equal with regards to their reliability. This
classification is reasonable if all objects are identical (e.g.,
video frames in a 30 frame/second film). Many applications, such as
...
... video frames in a 30 frame/second film). Many applications, such as
multimedia systems, however, often contain a variety of object types.
Thus three object reliability classes are proposed: BART-NL, BART-L,
and NBART-L. Objects are assigned to one of these classes ...
... equally, the sending and receiving functions of a protocol providing
partial order/partial reliability service will behave differently for
each class ...
... addition, this RFC describes the mechanisms needed to (3) initiate a
connection, (4) provide varying degrees of reliability for the
objects being transmitted, and (5) improve buffer utilization at the
...
... By extending the transport paradigm to allow partial ordering and
reliability classes, a user application may be able to take advantage
of a more efficient data transport ...
... profile may vary during the
connection as the order or reliability requirements of the user
change but this length must not exceed the buffering ...
... For the partial ordering to commence, the TCP must be made aware of
the acceptable object orderings and reliability for both the send-
side and receive-side of the connection for a given set of objects
...
... partial order and a vector has been proposed to communicate and
manage the reliability aspects of the service. Temporal values may
be included within the objects themselves or may be defined as a
...
... service profile would include (1) a partial
order matrix, (2) a reliability vector and (3) an object_sizes vector
...
... The reliability vector for the case where reliability classes are
enumerated types such as {BART-NL=1, BART-L=2, NBART-L = 3} and all
...
... delivery. The sending TCP ascertains the object ordering and
reliability from the service profile and uses this information in its
...
... receiver modifications are more
significant, particularly the issues of object deliverability and
reliability. And both sides will need to redefine the notion of
window management. Let us look specifically at how each side of the
...
... retransmission
timer. The only difference with a partial order service is that the
reliability vector must be examined to determine whether or not to
buffer ...
... Buffer management at the sending end of a partial order connection is
dependent upon the object reliability class and the object size.
When transmitting ...
... space (this is discussed further in Section 4.2.2). Moreover, it
should be noted that the introduction of partial ordering and partial
reliability presents several new and interesting alternatives for the
acknowledgment policy. The authors are investigating several of
these strategies through a simulation model and have included a brief
...
... receiving TCP has additional decisions to make involving object
deliverability, reliability and window management. Additionally, the
service ...
... based on traversing the precedence graph.
Consideration of object reliability is interesting. The authors have
taken a polling approach wherein a procedure is executed
periodically, say once every 100 milliseconds, to evaluate the
...
... than-ideal underlying networks can cause delays for applications that
need only partial order or partial reliability. By introducing a
partial order service, one may in effect relax the requirements ...
... service, one may in effect relax the requirements on
order and reliability and presumably expect some savings in terms of
buffer utilization and bandwidth ...
... flexibility of the partial order itself - specified by the PO matrix
and reliability vector. If the underlying network has no loss, a
...
... QOS flexibility to include
object delivery, reliability, and temporal value thus allowing the
transport layer to effectively handle a wider range ...
... TCP options
As evidenced by this list, a partial order and partial reliability
service proposes to re-examine several fundamental transport
mechanisms ...
... Conrad, P., Amer, P., and T. Connolly, "Improving Performance in Transport-Layer Communications Protocols by using Partial Orders and Partial Reliability", Work in Progress, December 1993. ...