DSCP (Differentiated Services Code Point)

It controls the Quality of Service (QoS). How routers and switches prioritize packets. It lives in the IP header, part of the “Differentiated Services” (DiffServ) field, which replaced the old TOS (Type of Service) byte. DSCP is a 6-bit field, giving 64 possible classes (0–63).

Each DSCP value corresponds to a traffic class. routers use it to decide:

1. Which queue to put the packet in.
2. Whether to forward, delay, or drop it during congestion.

Why it matters for media networks (like SMPTE 2110):

1. Keeps audio, video, and control streams separated by priority.
2. Ensures PTP (Precision Time Protocol) traffic isn’t delayed or dropped.
3. Switches/routers must be configured to honor DSCP markings—otherwise it’s ignored.

Common DSCP classes:

DSCP	Binary	Name	Typical Use
0	000000	Best Effort	Normal traffic
46	101110	EF (Expedited Forwarding)	Voice / PTP timing
34	100010	AF41	Video
18	010010	AF21	Low-latency data
10	001010	AF11	Background traffic

TTL (Time To Live) Purpose: Prevents packets from circulating forever in case of routing loops.
Where it lives: Also in the IP header (1-byte field).

How it works: TTL starts as a number (e.g., 64, 128, or 255). Every router that forwards the packet decrements TTL by 1. If TTL reaches 0, the router discards the packet and sends back an ICMP “Time Exceeded” message.

Why it matters: Controls the scope of packets, especially multicast: Small TTL (e.g., 1–5): keep traffic within a LAN or local subnet. Larger TTL (e.g., 64–128): allow packets to cross WANs or reach the Internet. Helps with traceroute — each hop reduces TTL and returns an ICMP message, letting you map the route.

In summary:
DSCP = how important your traffic is. Controls priority and QoS.
TTL = how far your traffic can travel. Controls scope and loop protection.