Hi. DSCP values are partly comprised of IP precedence values and partly of the remaining ToS bits. From what I understand, ToS is deprecated and those bits are now being used for other things, like DSCP.
"The Internet Engineering Task Force (IETF) has defined the siz most significant bits of the 1-byte ToS field as the DSCP." DSCP is backwards compatible with IP precedence. The IP precedence bits are the 3 MOST SIGNIFICANT bits in the ToS field. The DSCP bits are the IP precedence bits + the 3 next most significant bits (total of 6 bits). So the mapping looks like: Binary 000000 = IP precedence 0, DSCP 0 Binary 001000 = IP precedence 1, DSCP 8 Binary 010000 = IP precedence 2, DSCP 16 Or you could mix it up and have: Binary 001010 = IP precedence 1, DSCP 10 Based on that you should be able to figure out the entire mapping. The last 2 bits in the ToS field are used for Early Congestion Notification (ECN), so you can effectively set those to 0. So to ping with a DSCP value of 8, you would set the tos field to be 00100000 or decimal 32. Hope it helps. A good reference point is to go to Cisco's web site and search for "Implementing Quality of Service Policies with DSCP", they have a good section on the ToS byte and how it all breaks down. On Wed, 26 Mar 2003, Edson Manners wrote: > I currently nee to use ping with certain QoS values. We currently use dscp > values that are multiples of 8. eg. (0,8,16,24,32,40,48,56) > > The sprint man page though has a slightly different convention for nameing > these values and I cannot tell if there is some equivalent in there for sure. > Can someone please point me to where I can get more info or explain to m ehow > I can get to ping these different dscp values? > > Thanks. > > P.S. This was copied from the ping man page. > -Q tos Set Quality of Service -related bits in ICMP datagrams. tos can > be either decimal or hex number. Traditionally (RFC1349), these > have been interpreted as: 0 for reserved (currently being rede > fined as congestion control), 1-4 for Type of Service and 5-7 for > Precendence. Possible settings for Type of Service are: minimal > cost: 0x02, reliability: 0x04, throughput: 0x08, low delay: 0x10. > Multiple TOS bits should not be set simultaneously. Possible > settings for special Precedence range from priority (0x20) to net > control (0xe0). You must be root (CAP_NET_ADMIN capability) to > use Critical or higher precendence value. You cannot set bit > 0x01 (reserved) unless ECN has been enabled in the kernel. In > RFC2474, these fields has been redefined as 8-bit Differentiated > Services (DS), consisting of: bits 0-1 of separate data (ECN will > be used, here), and bits 2-7 of Differentiated Services Codepoint > (DSCP). > > -- > Education's purpose is to replace an empty > mind with an open one. - Unknown > Edson Manners > Academic Computing and Network Systems > Florida State University > > -- > Unsubscribe mailto:[EMAIL PROTECTED] > Help mailto:[EMAIL PROTECTED] > Archive http://www.ee.ethz.ch/~slist/smokeping-users > WebAdmin http://www.ee.ethz.ch/~slist/lsg2.cgi > -- Unsubscribe mailto:[EMAIL PROTECTED] Help mailto:[EMAIL PROTECTED] Archive http://www.ee.ethz.ch/~slist/rrd-users WebAdmin http://www.ee.ethz.ch/~slist/lsg2.cgi
