Describing network traffic
Knowing what traffic flows through the network matters less than being able to describe it in technical terms. These are the properties that matter.
Traffic characteristics
- Interactivity: a response is expected for the app to function. Some interactive apps tolerate delay, some don’t.
- Real-time responsiveness: data must arrive on time. Not necessarily interactive (a live sports stream, video conferencing).
- Amount of data: voice is low bandwidth (“benign bandwidth”), video streaming is “bandwidth greedy”.
- Burstiness: smooth apps generate a consistent amount of data. Bursty apps spike (web browsing: light for text pages, heavy during a big download).
- Drop sensitivity: how badly packet loss degrades the app. Real-time apps like video on demand are drop-sensitive.
- Criticality to business: subjective. Video surveillance might be top priority at one company, irrelevant at another.
Latency vs. jitter
Latency (often used interchangeably with delay) is the total time from source sending to destination receiving. It includes propagation delay through the media plus processing time on every device along the path.
Jitter is the variation in latency. Network conditions change, so some packets arrive faster than others.
Application categories
Batch
Bulk data transfer with no human involvement after kickoff. The user starts it and waits. Bandwidth affects how long it takes but isn’t critical: even a slow link finishes eventually.
Examples: FTP and TFTP file transfers, inventory updates, automated file replication. (FTP and TFTP are protocols per their RFCs, but the transfers they enable are typically batch-style workloads.)
Interactive
The user acts, then waits for a response. Human-to-machine. Response time matters more than for batch, but strict guarantees usually aren’t required: with less bandwidth the transaction just takes longer and still completes.
How much response time is acceptable depends on how important the app is to the business.
Examples: a database inquiry, a stock exchange transaction, online shopping.
Real-time
Voice and video, usually human-to-human. Bandwidth is critical and delivery is time-critical. Lost data is not retransmitted, so packet loss directly hurts quality.
Sufficient bandwidth is mandatory, and QoS is used to give this traffic higher priority (VoIP being the classic case).
Examples: voice, video conferencing, live streaming.
Mixed requirements in one application
A single application can carry multiple traffic types. Factory automation is the classic example: sensor readings and alarms need guaranteed delivery and a prescribed response time, while device configuration and commercial data from the same application are not time-critical.