Internet

Network Edges(host)

1. end systems
2. access network(机构网络、家庭网络)
3. links(media:光纤 etc)

Network Core(router)

1. packet switch(包交换，线路不定 store&forward)
2. circuit switch(路线固定)
3. network structure

Delay

1. transportation delay
2. prop delay

Layers

...

Service Model

client-server