The Network Layer is the third layer in the OSI Model, The Network Layer is crucial for the transfer of data from one host to another located in different networks. It provides the means for routing packets across network boundaries, thus ensuring appropriate data transmission.
Global inter-networking protocol
Single standard network layer protocol (IP) • Packet switched network, best effort service • Uniform network and host addressing • Uniform end-to-end connectivity – subject to firewall policy
Many transport & application layer protocols Range of link-layer technologies supported
This is beneficial as it decouples end-to-end functionality from per-hop functionality allowing it to traverse between multiple networks
Forwarding
Best effort, connectionless, packet delivery
- Just send – no need to setup a connection first
- Network makes its best effort to deliver packets, but provides no guarantees
- Time taken to transit the network may vary
- Packets may be lost, delayed, reordered, duplicated or corrupted
- The network discards packets it can’t deliver Easily run over any type of link layer
IP
Real Time Traffic
Video streaming dominates Internet traffic, growing per year
- Packet loss → Quality impairments or increased delay
- Driving centralisation and direct CDN connections → Easier to manage quality
- Driving TCP congestion control and TCP replacements → BBR algorithm, QUIC; low-latency
Interactive real-time media has stricter constraints
- WebRTC, Zoom, VoIP, gaming, … → Non-TCP transport used to lower latency
Impact of Covid-19
Residential networks saw increase in traffic overnight at the start of the COVID-19 lockdown, Mobile networks saw drop in traffic. Video conferencing providers saw massive growth in traffic fortunately the Internet was flexible enough to support this shift – can we maintain such flexibility while also improving quality? → Innovation in the Network
Changing Internet and the effects:
The original design of the Internet made certain assumptions:
- Devices are generally located in a fixed location, and have a small number of network interfaces that are uniquely addressable
- The network and services are decentralized
- Best effort service provides sufficient quality
- The network is trusted
- Innovation can happen at the edges; the network is dumb