What is DiffServ?

DiffServ stands for "Differentiated Services" and is a model that signals the priority of the data packets. DiffServ is based on the Type of Service (ToS) field and uses the same byte in the IP header.

ToS uses the first three bits to denote the precedence of 0 to 7, and four more bits (the ToS bits) to optimize the data flow (including “low delay” and “high reliability”). This model is rather inflexible and has been little used in the past.

The DiffServ model uses the first 6 bits to distinguish different classes. This allows up to 64 differentiated services code points (DSCPs), which allow a finer prioritization of the data flow:

With the class "Expedited Forwarding" marks those packets that are to be transmitted before all other packets (preferred).

Codepoint DSCP bits Dec.   Codepoint DSCP bits Dec.   Codepoint DSCP bits Dec.
CS0 (BE) 000000 0   AF11 001010 10   AF33 011110 30
CS1 001000 8   AF12 001100 12   AF41 100010 34
CS2 010000 16   AF13 001110 14   AF42 100100 36
CS3 011000 24   AF21 010010 18   AF43 100110 38
CS4 100000 32   AF22 010100 20   EF 101110 46
CS5 101000 40   AF23 010110 22        
CS6 110000 48   AF31 011010 26        
CS7 111000 56   AF32 011100 28        

www.lancom-systems.com

LANCOM Systems GmbH | A Rohde & Schwarz Company | Adenauerstr. 20/B2 | 52146 Wuerselen | Germany | E‑Mail info@lancom.de

LANCOM Logo