Computer Networks · free preview
Presentation Formatting
Two machines that agree on protocols can still disagree on what the bytes mean, since architectures store integers in different byte orders and compilers pad structures differently, so presentation formatting encodes application data into a wire representation and decodes it at the far end, a design space taxonomized by which data types are supported, whether conversion follows a canonical intermediate form or lets the receiver make right, whether messages carry type tags or rely on stubs that already know the shape, and whether the stubs are compiled or interpreted, with XDR, ASN.1, NDR, and protocol buffers as the canonical inhabitants of the space and XML as the self-describing extreme.
1. The Disagreement Among Machines
The Disagreement Among Machines
2. A Taxonomy of Encodings
A Taxonomy of Encodings
3. Four Systems, Four Corners
Four Systems, Four Corners
4. The Self-Describing Extreme
The Self-Describing Extreme
5. The byte-order trap
A little-endian host sends the 32-bit integer 1 as raw memory bytes to a big-endian host. What does the receiver read?
6. The padded structure
Why can't a program simply write an in-memory structure to the network?
7. Two conversion strategies
What is the trade between canonical intermediate form and receiver-makes-right?
8. What tags buy
What does tagging the data in a message buy, and at what price?
9. Matching systems to axes
Which pairing of system and design choices is correct?
10. The markup trade
Why do loosely coupled web services gravitate toward markup languages rather than compact binary encodings?
11. The byte order names
What are the two byte orders called, one storing the most significant byte first and one the least significant first?
12. The one standard form
In which conversion strategy does every host translate its data to and from a single agreed external representation?
13. The opposite duty
In which strategy does the sender transmit its native format and the receiver perform whatever conversion is needed?
14. The self-describing message
What does a message carry when its type information travels inside the message itself rather than in a pre-shared stub?
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