1. Congestion Control: BBR vs Cubic
TCP is not a fixed protocol; it is an Evolving Algorithm. The math of how a connection grows its window determines how it handles congestion.
The Cube and the Model
Cubic (Loss-Based)
Cubic fills the network buffers until a packet drops. This causes 'Bufferbloat'—increased RTT for everyone sharing the link. Use case: Standard web traffic.
BBR (Rate-Based)
BBR measures the physical bottleneck bandwidth. It paces packets to never exceed the pipe's capacity, keeping buffers empty and RTT at the minimum physical limit. Use case: Youtube / Netflix.
2. QUIC Forensics: Connection Migration
Standard TCP dies when your IP changes. QUIC (HTTP/3) survives by decoupling the connection from the network address using Connection Identifiers (CIDs).
Bit-Level Migration Detection
When an IP switch occurs, the new UDP source IP is seen. Forensics tools must look for the PATH_CHALLENGE frame. If the Destination CID matches the previous flow, it is a Migration event, not a new session. Tracking this allows for seamless session reconstruction across heterogeneous networks.
Payload: PATH_CHALLENGE [Data=0x4a2...]
3. Head-of-Line Blocking: The Invisible Wall
In a TCP stream, packet #1 is the gatekeeper. If it drops, packets #2 through #1,000 are held in the kernel buffer, effectively frozen.
SCTP (Multi-Streaming)
Loss in Stream A has ZERO impact on Stream B. Each stream has its own head of line. Perfect for signaling/voice.
MPTCP (Multipath)
Splits traffic across paths, but forces everyone back into a single sequence. One slow path kills the global speed.
Frequently Asked Questions
Technical Standards & References
Related Engineering Resources
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