Anti-DDoS protection explained

Anti-DDoS protection is a set of detection and mitigation methods that defend a network against Distributed Denial of Service attacks aimed at exhausting bandwidth, network device resources or application capacity. For a network operator (ISP, ASN) effective protection means keeping links and services available even when traffic many times the normal load is directed at a single IP address. A well-designed system pairs continuous telemetry monitoring with automated response that triggers before the attack saturates the uplink.

Types of DDoS attacks

Attacks are usually grouped into three categories by the layer they stress. The distinction matters in practice, because each category calls for a different mitigation method.

• Volumetric: flood the link with sheer traffic volume, typically through UDP amplification (DNS, NTP, memcached, SSDP). Measured in Gb/s or Tb/s.
• Protocol: exhaust the state tables of firewalls, load balancers and servers. Classic examples are SYN flood, ACK flood and IP fragmentation. Measured in packets per second (pps).
• Application-layer (Layer 7): seemingly valid HTTP requests, DNS queries or login attempts that overwhelm the application at low volume. Hard to tell apart from legitimate traffic.

Detection and telemetry

Attack detection relies mainly on flow analysis exported from edge routers: NetFlow, IPFIX or sFlow. A collector builds a baseline of normal traffic for prefixes and services, then flags anomalies: a sudden spike of pps or bps toward a single /32, an unusual spread of source ports, the dominance of one protocol. Streaming telemetry (for example gNMI) shortens reaction time compared with SNMP polling. Detection has to work in seconds rather than minutes, because a volumetric attack can saturate an uplink almost instantly.

Mitigation methods

• Scrubbing: divert traffic to a cleaning center that drops attack packets and returns legitimate traffic over a tunnel (GRE) or a dedicated link. The most selective method.
• RTBH (Remotely Triggered Black Hole): announce a prefix over BGP with a blackhole community so traffic to the targeted address is dropped at the network edge or at an upstream provider. Effective, but it also cuts legitimate traffic to that address.
• BGP FlowSpec: distribute granular filtering rules (address, port, protocol, packet length) over BGP, which blocks only attack traffic instead of an entire prefix.
• Anycast: spread the same prefix across many locations so the attack volume is distributed geographically and absorbed locally.

On-prem vs cloud, and choosing a provider

On-prem solutions (scrubbing appliances inside the operator network) offer the lowest latency and full control, but are bounded by the capacity of your own uplinks. An attack larger than the link floods it before the hardware can act. Cloud or remote scrubbing absorbs attacks of hundreds of Gb/s and beyond, because the provider holds distributed capacity, but it adds latency and a dependency on BGP integration. Many operators run a hybrid model: local appliances handle smaller attacks while larger ones are diverted to the cloud automatically. When choosing a provider, assess link capacity and the number of scrubbing points, support for RTBH and FlowSpec, the time-to-mitigate committed in the SLA, Layer 7 handling and the transparency of attack reporting.