QoS: Class Selector PHB and DSCP Values

Since the DSCP field overlaps with the previously defined IPP field within the ToS byte, RFC 2475 defines a set of DSCP values and PHBs called Class Selector (CS) PHBs which provide backward compatibility with IPP.  So if a router sets the CS DSCP value, and another devices looks only at the IPP field, it will make sense from an IPP perspective.

CSDSCP.PNG

CS DSCP value PHBs suggest that the larger values should be given better queueing preference than packets with lower CS DSCPs.

 

Advertisements

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s