Lecture 1 Intro

What is a Network

An infrastructure that allows distributed users to communicate with each other
Building Block: node -> link -> node
Scaling the network
Message Switching Architecture
- Store-and-Forward operation
  - Messages were decoded
  - Next-hop in route determined by destination address of a message
  - Each message was carried by hand to next line
Circuit Switching
- Source first establishes a connection (circuit) to destination
- Source sends the data over the circuit
- Predictable performance (Fast and simple data transfer)
- Circuit will be idle for significant periods of time
Packet Switching
- Source sends information as self-contained messages that have an address
- Each packet transfers independently to destination

What is the Internet

Inter-net: network of networks
Enable communication between diverse applications on diverse devices
Over very diverse infrastructures: WIFI, cellular, data center networks, corporate networks
Application needs/demands
- Traffic data rate and loss sensitivity
- Traffic pattern
- Traffic target
Multiplexing
- Need to share network resources

Internet Design

In order to inter-operate, all participating networks must follow a common set of rules
Service Model: the commitment made to applications
Standards allow players to share risk and benefits of a new market *e.g., 802.11 LAN, UP, HTTP/SMTP