Enter a DSCP class (EF, AF41, CS6), a DSCP value (0–63), or a ToS/DS byte in hex (0xB8) or decimal. Get the class name, DSCP bits, the full ToS byte, and IP precedence.
| Class | DSCP | Bits | ToS hex | Typical use |
|---|
The second byte of the IPv4 header was originally the Type of Service (ToS) byte. RFC 2474 redefined its upper 6 bits as the DSCP (Differentiated Services Code Point) and the lower 2 bits as ECN. So the DSCP value occupies bits 0–5 of the DS field, and the ToS byte equals DSCP × 4 (a left shift of 2).
That's why EF (DSCP 46) shows up as ToS 0xB8, and CS6 (DSCP 48) as 0xC0 — values you'll recognize from show policy-map output and packet captures.
CS0–CS7 (Class Selector) are backward-compatible with the old 3-bit IP Precedence. AFxy (Assured Forwarding) encode a class x (1–4) and a drop precedence y (1–3). EF (Expedited Forwarding) is the low-latency class for voice. Default/BE is DSCP 0.
Yes. EF (Expedited Forwarding) is DSCP 46, binary 101110, ToS byte 0xB8.
IP precedence is the top 3 bits of the DS field. The Class Selector code points (CS0–CS7) map one-to-one onto the eight precedence values for backward compatibility.
They carry ECN (Explicit Congestion Notification), independent of DSCP. This tool reports the DSCP and the resulting ToS byte with ECN bits as 0.