3. Axioms/Fallacies

Question 1

What is an Axiom?

Answer 1

Statements that are self-evidently True

Question 2

Axioms (8)

Answer 2

Latency is greater than zero

Bandwidth is less than infinite

Transport cost is greater than 0

There is more than one adminstrator

Topology does change

The network is not homogeneous

The network is not secure

The network is not reliable

Question 3

Basic desiderata (good features we desire) for message passing?

How are these achieved?

Answer 3

Low latency: fast travel source to target.
High throughput: many messages at the same time.
Inexpensive Transport: using interconnect should not be onerous

Achieved through per-network management.

Question 4

Main Levers of per-network management for engineering performance?

Answer 4

Topology: allows variation as to how nodes are linked.
Heterogeneous: resources deployed to best effect.
Preserve Security

Question 5

What is a fallacy?

Answer 5

Wrongly Believed to be True

Question 6

Implications of Axioms? (8)

Answer 6

latency greater than 0: send fewer, larger, more significant messages

Bandwidth less than infinite: In WAN we hog bandwidth

Transport cost greater than zero: only go through the interconnect if benefits outweigh cost

More than one administrator: local isolated decisions take without consultation, creating barriers to communication

Change in topology: One should not depend on specific endpoints or pre-computed routes

Network not homogeneous: abstraction and interoperability are imperative

Network not secure: risk of viruses and infection

Network not reliable: policy to counteract failure such as redundancy through caching and replication