TOS and DSCP Field in IP packet

Posted: August 3, 2013 in Uncategorized

Today i learned about one of new filed in IP(Internet Protocol) Packet. Since these fields were new to me and after knowing about i became eager to post about it.

TOS – Type of Service :

Its 8 bit field in IPv4 packet.

DSCP  – Differentiated Services Code Point Or DiffServ :

Its the same part of the above field TOS. Its derived from the TOS field. The 1st 6 bits of TOS field has been described as DSCP field value. Even after defining the DSCP values, the old values and definition of TOS values have been retain to maintain backward compatibility. There are different classes defined under it to process ip packets and decide which packet should be given priority to deliver. More info from Wikipedia.

Detail IPv4 packet Header Information is at link.

TOS-DSCP Conversion can be found at Site.

Other Table for TOS-DSCP conversion.

DSCP  and TOS fields as seen in Wireshark:

Source

Other places to look for :

i) http://bogpeople.com/networking/dscp.shtml

ii) http://blog.webdir.bg/tos-to-dscp-mapping/

iii) Info from Cisco site

iv) Doc

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