What comprises a network?
This is the start of a series of blog posts focusing on Network Functions Virtualization (NFV) the transformation of the telecommunication industry. This blog post can also be heard at https://thenfvpodcast.org/what-comprises-a-network/
A large network is comprised of an IP backbone, Enterprise, SMB, residential wifi and public cellular networks.
- IP backbone – the core / central / backbone network
- Distribution networks – connect access networks to the core
- Access networks – provide access to computers, servers, mobile devices.
- Ethernet – Cables used to connect servers and workstations, buildings and campuses, up to 100gig and soon 400.
- Wide Area Networks -Typically T1 and ATM though in the future to will likely be supplanted by Ethernet.
- WIFI – Wireless networks used in the home, public space and Enterprise.
- Cellular – Four generations 1G,2G,3G,4G – Each generation becomes faster adds encryption and channels. One day 5G will have more intelligence, Quality of Service, adaptive network reconfiguration etc
- Unified communication – One platform that unifies web, video, audio, telephony instant messenger etc.
There are essentially two types of network traffic:
- Elastic traffic adapts to changes in delay and throughput the network – example FTP, HTTP, SSH. Though painful, I can wait for a webpage to load over HTTP or file to download over FTP. TCP is an example of a protocol that controls congestion in the network.
- Inelastic traffic does not adapt to changes in delay and throughput – example voice, media, video and airline pilot simulation. Anyone watching a video online and the image is choppy or blurry or listening to an audio broadcast or participating in voice of IP phone call and the sound breaks up and words are skipped has experienced inelastic traffic.
Reliable network traffic communication needs:
- A minimum throughput
- No delay – for example pricing of stocks on an exchange cannot be delayed, traders need realtime communication
Delay can be described by
- delay jitter – Is the magnitude of delay variation – incoming packets are buffered to compensate and for Internet delays and then steadily streamed to the application expecting the traffic.
- packet loss- RealTime applications generally expect no traffic loss. Again, think of those lost words in an internet phone call or imagine data lost by a financial trading network.
Quality of Service
How good/bad/average is the service I am providing? Perspective of the service provider.
- What is throughput – bytes per second for logical traffic flow
- Is there any delay – average or max delay , latency
- What is the packet jitter – max allowable jitter
- What is the error rate – What fraction of bits are delivered in error
- Packet loss – What fraction of packets are lost
- Priority – How do I prioritize flows of traffic
- Availability – What % of the time is my service available? Over 365 months was my service up for 363?
- Security – Is my service secure? What levels of security do I offer?
Quality of Experience
What is the user experience? Perspective of the end user who is using the service.
- Perceptual – Sensory experience of the user. How the user perceives the video: sharpness, brightness, flicker and the audio: clarity and timbre.
- Psychological – What is the ease of use: Is the service a joy to use? Is it useful? What is the perceived quality / satisfaction. Is the user annoyed by poor service quality?
- Interactive – If the application requires interaction for example the user speaking how responsive / natural / communicative / expressive is the user experience?