|TCP option 10, Partial Order service profile|
|Protocol type:||Transport layer protocol.|
|Option length:||3 bytes.|
|Links:||IANA: TCP option numbers.|
RFC 1693, pg. 1:
A service which allows partial order delivery and partial reliability is one which requires some, but not all objects to be received in the order transmitted while also allowing objects to be transmitted unreliably (i.e., some may be lost).
The realization of such a service requires, (1) communication and/or negotiation of what constitutes a valid ordering and/or loss-level, and (2) an algorithm which enables the receiver to ascertain the deliverability of objects as they arrive. These issues are addressed here - both conceptually and formally - summarizing the results of research and initial implementation efforts.
RFC 1693, pg. 19:
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 (hereafter referred to as a "period"). This information is contained in the service profile and it is the responsibility of the user application to define this profile. Unlike standard TCP where applications implicitly define a reliable, ordered profile; with partial order TCP, the application must explicity define a profile.
|MAC header||IP header||TCP header||TCP option 10||Data|
TCP Option 10:
Kind. 8 bits. Set to 10.
Length. 8 bits. Set to 3.
SF, Start Flag.
This bit indicates that the information in the data section represents the beginning of the service profile. For service profiles which fit completely in a single segment, both flags will be set to 1. Otherwise, the Start flag is set in the initial segment and the End flag in the final segment allowing the peer entity to reconstruct the entire service profile (using the normal sequence numbers in the segment header).
EF, End Flag.
Indicates that the information in the data section represents the end of the service profile.
This field serves merely to complete the third byte of the option.
[RFC 1693] An Extension to TCP : Partial Order Service.