transport
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... reliable connections which guarantee all objects will be delivered
verses unreliable data transport which makes no guarantee. What is
more appropriate for some applications is a partial order and/or
partial reliability ...
... streams (e.g., displays of multiple overlapping and nonoverlapping
windows). These applications have a high degree of tolerance for
less-than-fully-ordered data transport as well as data loss. Thus
they are ideal candidates for using a partial order, partial
...
... network is completely
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 ...
... are four distinct salespersons. If record 2 is received before
record 1 due to a network loss during transmission, the transport
service can not deliver it and must therefore buffer it until record
1 arrives. An ordered service ...
... delivery orderings would satisfy the application, or from the
transport layer's point of view, all records are immediately
deliverable as soon as they arrive from the network. No record needs
...
... Delivery
It is vital for the transport layer to recognize the exact
requirements of the application and to ensure that these are met.
...
... receiving application refreshes windows as soon as the transport
service delivers them. If the windows are configured as in Figure
4a, then there exist two different orderings for redisplay, namely
1,2,3,4 or 1,3,2,4. If window 2 is received before window 1, the
...
... 4a, then there exist two different orderings for redisplay, namely
1,2,3,4 or 1,3,2,4. If window 2 is received before window 1, the
transport service cannot deliver it or an incorrect image will be
displayed. In Figure 4b, the structure of the windows results in six
...
... upon, and must be specified by the application. Intuitively, as the
number of acceptable orderings increases, the amount of resources
utilized by a partial order transport service, in terms of buffers
and retransmissions ...
... and retransmissions, should decrease as compared to a fully ordered
transport service thus also decreasing the overall cost of the
connection. Just how much lower will depend largely upon the
...
... considered.
While classic transport protocols generally treat all objects
equally, the sending and receiving functions of a protocol providing
...
... segments to determine which, if any, octets
are deliverable and which are not). At the other extreme, the
transport protocol could maintain object atomicity regardless of size
- passing arbitrarily large data structures to IP ...
... upper-layer interface. Of course this presents some
additional complexities. First of all, the transport layer will now
have to be concerned with fragmentation/reassembly of objects larger
...
... reliability classes, a user application may be able to take advantage
of a more efficient data transport facility by negotiating the
optimal service level which is required - no more, no less. This is
...
...
The first option represents a simple indicator communicated between
the two peer transport entities and needs no further explanation.
The second option serves to communicate the information necessary to
carry out the job of the protocol - the type of information which is
...
... service would necessarily require that significantly more control
information be passed between transport entities at certain points
during a connection. Maintaining the strict interpretation of this
...
... connection
as described in Section 4.1. After which, although both ends have
acknowledged the acceptability of partial order transport, neither
has actually begun a partial order transmission - in other words,
both the sending-side and the receiving ...
... service profile is one of the concerns for
the transport protocol. It would be useful if the TCP could encode a
partial ordering in as few bits ...
... receiving application must transmit the new object numbering to the
sending application (not the sending transport layer). Since the
sending application must receive this information in any case, it
simplifies matters greatly to require that the sending application be
...
... the only side that may specify the service profile to the transport
layer.
Consider now the layered architecture ...
... delivery refers to
the ability to transfer less-than-complete objects between the
transport layer and the user application (or session layer as the
...
... performance gains, (2) identify new issues unique to partial order
transport and, (3) build a road-map for application designers
interested in using a partial order service.
...
... service and
discusses the practical issues involved with including partial
ordering in a transport protocol. The need for such a service is
motivated by several applications including the vast fields of
...
... delivery, reliability, and temporal value thus allowing the
transport layer to effectively handle a wider range of applications
(i.e., any which might benefit from such mechanisms). The service ...
... partial order service (which encompasses the two extremes of total
ordered and unordered transport as well).
Several significant modifications have been proposed and are
...
... application-dependent partial ordering
(2) Allowing unreliable and partially reliable data transport
(3) Conducting a non-symmetrical connection ...
... reliability
service proposes to re-examine several fundamental transport
mechanisms and, in so doing, offers the opportunity for substantial
improvement in the support of existing and new application areas.
...
... Amer, P., Chassot, C., Connolly, T., and M. Diaz, "Partial Order Transport Service for Multimedia Applications: Reliable Service", Second International Symposium on High Performance Distributed Computing (HPDC-2), Spokane, Washington, July 1993. ...
... Amer, P., Chassot, C., Connolly, T., and M. Diaz, "Partial Order Transport Service for Multimedia Applications: Unreliable Service", Proc. INET '93, San Francisco, August 1993. ...
... 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. ...
... Chang, Y., "High-Speed Transport Protocol Evaluation -- the Final Report", MCNC Center for Communications Technical Document, February 1993. ...