Improvement suggestion for datagram vs virtual-circuit

[GregoryVds]

Hello,

I think it could be interesting to add a small section that compares the datagram vs the virtual-circuit organisation for the network layer. Both have advantages/disadvantages compared to the other and different use cases. The book clearly explain how both organisation work but doesn't really explain why use one over the other.

I think it would be nice to highlights some aspects like:

• Setup overhead vs no setup
• State maintained in routers vs no state in routers
• A router failure break the circuit vs no issue of routeur failure in datagram organisation
• Easier congestion/quality of service control vs difficult

And also maybe give some examples of virtual-circuit use cases like: routing inside ISPs, long-live VPNs between corporate offices, etc.

Gregory