I am wondering if we can set/mark a packet header with non-recommended DSCP value. With Wireshark I can see that packet is marked "Unknown DSCP". So my question is "is it necessary to set the recommended value of DSCP always ?
For Example. If I am setting DSCP to 62 its showing unknown DSCP. Whereas if I set 32 or 40 or other mentioned in list , it's giving me name of proper class.
Will the packed be dropped or sent with default priority ?
As wireshark says, it's "unknown", not "malformed". It's perfetly OK to use a non-recommended DSCP values: as is often (if not always) the case you have a range for experimental values, for instance if you work at Cisco or Huawey and develop new equipment.
- IANA Considerations
The DSCP field within the DS field is capable of conveying 64 distinct codepoints. The codepoint space is divided into three pools for the purpose of codepoint assignment and management: a pool of 32 RECOMMENDED codepoints (Pool 1) to be assigned by Standards Action as defined in [CONS], a pool of 16 codepoints (Pool 2) to be reserved for experimental or Local Use (EXP/LU) as defined in [CONS], and a pool of 16 codepoints (Pool 3) which are initially available for experimental or local use, but which should be preferentially utilized for standardized assignments if Pool 1 is ever exhausted.
(emphasis mine)
As to what happens to traffic with such non-standard values, it's treated with default priority by equipment that do not recognize it:
- Differentiated Services Field Definition
[...]
Packets received with an unrecognized codepoint SHOULD be forwarded as if they were marked for the Default behavior (see Sec. 4), and their codepoints should not be changed. Such packets MUST NOT cause the network node to malfunction.
So it is indeed experimental: don't expect interoperability, it will be ignored (but preserved, though).
Source: rfc2474 https://www.rfc-editor.org/rfc/rfc2474
