Transport Protocols for Department of Defense Data Networks Report to the Department of Defense and the National Bureau of Standards (1985) / Chapter Skim
Currently Skimming:
3 Comparison of DOD and ISO Protocols
3 Comparison of DOD and ISO Protocols
Pages 13-24
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 13... ...
A second much simpler protocol, the User Datagram Protocol (UDP) , providing datagram or connectionless service at the transport layer is also briefly considered.
|
From page 14... ...
Both octet and segment units of flow control can be argued to have their advantages for different types of application. The former makes it easy to indicate buffering limits in terms of total bytes (appropriate for stream transfer)
|
From page 15... ...
The impact is likely to be minimal, but this is an open area of the ISO specifications that may need further definition for use by DOD. Binding User Entities to Connections TCP requires a prior Listen Request from a user entity for it to be able to accept an incoming connection request.
|
From page 16... ...
The TCP urgent messages are sent requesting expedited service from the network layer so network bottlenecks can be bypassed as well. TP-4 allows users to send expedited data units carrying up to sixteen octets of user data.
|
From page 17... ...
The DOD protocol architecture assigns the security-marking function to the IP layer and provides an [l-byte security option with a defined coding in the IP header. TP-4 provides a variable-length security option carried in Call Request packets.
|
From page 18... ...
A separate ISO datagram protocol similar to UDP has been defined and is expected to become a draft proposed standard in June 1984. Closing TOP provides a graceful closing mechanism that ensures that all data submitted by users are delivered before the connection is terminated.
|
From page 19... ...
Despite the difficulties, protocol designers have developed several metrics for comparing transport protocols. These view protocol performance from a variety of perspectives, including (~)
|
From page 20... ...
Both permit credits to be granted "optimistically," permitting receiver buffers to be shared over several transport connections and permitting credit reduction in the event of buffer congestion. Both permit optimizing protocol efficiency by delaying controlmessage traffic when it does not need to be transmitted, combining it with later data or control traffic.
|
From page 21... ...
performance degradation due to untuned application protocols. This list of risks comes from experience in implementing computer networks based on the DOD protocols and proprietary commercial protocols.
|
From page 22... ...
The areas of ambiguity in protocol specifications are typically only of concern to protocol implementors. The current protocol implementors through much of the world are typically using the NBS formal specifications as a basis of their implementations of TP-4 and have access to the NBS test tools for certifying their implementations.
|
From page 23... ...
Based on the availability of the NBS test tools and formal protocol specification for TP-4, the committee did not see any significant risk of errors in implementing TP-4. Performance Issues The largest risk in implementing TP-4 concerns the performance of the implementations.
|
From page 24... ...
: ~ bits Header checksum: l6 bits Network Layer Protocol ID: ~ bits tGenerate3 Error flag Type: 5 bits Total Length* : 16 bits Source address length: ~ bits Source address: var.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.