1, Network overview:
The network into two levels, is the subnet connected with the switch, a router is connected to the Internet.
Internet Internet is a specific Internet internet
Development Stage 3, Stage 3: ISP, Internet service providers, payment of fees to obtain an IP address.
2, a packet-switched Internet composition
+ = Composition core edge: edge computer (end system), core router.
edge
End of two kinds of communication systems: client-server, peer 2 peer-peer mode
core
The most critical: Router
The key component implementation of packet switching, forwarding for storage, delivery destination host.
exchange:
Circuit switched: telephone connection, telephone exchange switch, to take up a link, the communication resource occupancy end. So one way to be fully occupied paragraphs job.
Packet switching: in packet units, storage - forwarding the data into smaller segments, together with the header information, are transmitted to the receiving end.
You can dynamically allocate bandwidth on the link occupancy paragraph by paragraph, independent and flexible without establishing a connection.
It will produce overhead delay, additional head.
Packet switching: telegraph exchange. Is used in an intermediate form, there is a store and forward, but not packet.
3, performance indicators
Rate, bandwidth, throughput, latency (delay transmission (transmission delay), the propagation delay, processing delay, queuing delay), delay-bandwidth product, round trip time, channel utilization, network utilization
Narrowband vs Broadband: the same bit rate spread, as the vehicle speed, the grid spacing is shorter, there is provided a transmission rate. Serial transmission is not parallel.
Round-trip time can be tested with Ping.
4, Architecture
Network complexity: hierarchical, network heterogeneity: the agreement.
Must be the same level, there is a consensus each layer (protocol), to the lower layer, a physical communication at the bottom, the peer communication logic, not the non-peer communication layer.
OSI / RM model, TCP / IP model. The application layer, transport layer TCP, the network layer IP. The following is a link layer and physical layer.