DCB-APP(8) Linux DCB-APP(8)
NAME
dcb-app - show / manipulate application priority table of the DCB (Data
Center Bridging) subsystem
SYNOPSIS
dcb [ OPTIONS ] app { COMMAND | help }
dcb app { show | flush } dev DEV [ default-prio ] [ ethtype-prio ]
[ stream-port-prio ] [ dgram-port-prio ] [ port-prio ] [ dscp-
prio ] [ pcp-prio ]
dcb app { add | del | replace } dev DEV [ default-prio PRIO-LIST
] [ ethtype-prio ET-MAP ] [ stream-port-prio PORT-MAP ] [ dgram-
port-prio PORT-MAP ] [ port-prio PORT-MAP ] [ dscp-prio DSCP-MAP
] [ pcp-prio PCP-MAP ]
PRIO-LIST := [ PRIO-LIST ] PRIO
ET-MAP := [ ET-MAP ] ET-MAPPING
ET-MAPPING := ET:PRIO
PORT-MAP := [ PORT-MAP ] PORT-MAPPING
PORT-MAPPING := PORT:PRIO
DSCP-MAP := [ DSCP-MAP ] DSCP-MAPPING
DSCP-MAPPING := { DSCP | all }:PRIO
PCP-MAP := [ PCP-MAP ] PCP-MAPPING
PCP-MAPPING := PCP:PRIO
ET := { 0x600 .. 0xffff }
PORT := { 1 .. 65535 }
DSCP := { 0 .. 63 }
PCP := { 0(nd/de) .. 7(nd/de) }
PRIO := { 0 .. 7 }
DESCRIPTION
dcb app is used to configure APP table, or application priority table in
the DCB (Data Center Bridging) subsystem. The APP table is used to as-
sign priority to traffic based on value in one of several headers:
EtherType, L4 destination port, or DSCP. It also allows configuration of
port-default priority that is chosen if no other prioritization rule ap-
plies.
DCB APP entries are 3-tuples of selector, protocol ID, and priority. Se-
lector is an enumeration that picks one of the prioritization name-
spaces. Currently it mostly corresponds to configurable parameters de-
scribed below. Protocol ID is a value in the selector namespace. E.g.
for EtherType selector, protocol IDs are the individual EtherTypes, for
DSCP they are individual code points. The priority is the priority that
should be assigned to traffic that matches the selector and protocol ID.
The APP table is a set of DCB APP entries. The only requirement is that
duplicate entries are not added. Notably, it is valid to have conflict-
ing priority assignment for the same selector and protocol ID. For exam-
ple, the set of two APP entries (DSCP, 10, 1) and (DSCP, 10, 2), where
packets with DSCP of 10 should get priority of both 1 and 2, form a
well-defined APP table. The dcb app tool allows low-level management of
the app table by adding and deleting individual APP 3-tuples through add
and del commands. On the other hand, the command replace does what one
would typically want in this situation--first adds the new configura-
tion, and then removes the obsolete one, so that only one prioritization
is in effect for a given selector and protocol ID.
COMMANDS
show Display all entries with a given selector. When no selector is
given, shows all APP table entries categorized per selector.
flush Remove all entries with a given selector. When no selector is
given, removes all APP table entries.
add
del Add and, respectively, remove individual APP 3-tuples to and from
the DCB APP table.
replace
Take the list of entries mentioned as parameter, and add those
that are not present in the APP table yet. Then remove those en-
tries, whose selector and protocol ID have been mentioned as pa-
rameter, but not with the exact same priority. This has the ef-
fect of, for the given selector and protocol ID, causing that the
table only contains the priority (or priorities) given as parame-
ter.
PARAMETERS
The following table shows parameters in a way that they would be used
with add, del and replace commands. For show and flush, the parameter
name is to be used as a simple keyword without further arguments.
default-prio PRIO-LIST
The priority to be used for traffic the priority of which is oth-
erwise unspecified. The argument is a list of individual priori-
ties. Note that default-prio rules are configured as triplets
(EtherType, 0, PRIO). dcb app translates these rules to the sym-
bolic name default-prio and back.
ethtype-prio ET-MAP
ET-MAP uses the array parameter syntax, see dcb(8) for details.
Keys are EtherType values. Values are priorities to be assigned
to traffic with the matching EtherType.
stream-port-prio PORT-MAP
dgram-port-prio PORT-MAP
port-prio PORT-MAP
PORT-MAP uses the array parameter syntax, see dcb(8) for details.
Keys are L4 destination port numbers that match on, respectively,
TCP and SCTP traffic, UDP and DCCP traffic, and either of those.
Values are priorities that should be assigned to matching traf-
fic.
dscp-prio DSCP-MAP
DSCP-MAP uses the array parameter syntax, see dcb(8) for details.
Keys are DSCP points, values are priorities assigned to traffic
with matching DSCP. DSCP points can be written either directly as
numeric values, or using symbolic names specified in
/etc/iproute2/rt_dsfield (however note that the file specifies
full 8-bit dsfield values, whereas dcb app will only use the
higher six bits). dcb app show will similarly format DSCP values
as symbolic names if possible. The command line option -N turns
the show translation off.
pcp-prio PCP-MAP
PCP-MAP uses the array parameter syntax, see dcb(8) for details.
Keys are PCP/DEI. Values are priorities assigned to traffic with
matching PCP/DEI. PCP/DEI values are written as a combination of
numeric- and symbolic values, to accommodate for both. PCP always
in numerical form e.g 0 .. 7 and DEI in symbolic form e.g 'de'
(drop-eligible), indicating that the DEI bit is 1 or 'nd' (not-
drop-eligible), indicating that the DEI bit is 0. In combination
2de:1 translates to a mapping of PCP=2 and DEI=1 to priority 1.
EXAMPLE & USAGE
Prioritize traffic with DSCP 0 to priority 0, 24 to 3 and 48 to 6:
# dcb app add dev eth0 dscp-prio 0:0 24:3 48:6
Add another rule to configure DSCP 24 to priority 2 and show the result:
# dcb app add dev eth0 dscp-prio 24:2
# dcb app show dev eth0 dscp-prio
dscp-prio 0:0 CS3:2 CS3:3 CS6:6
# dcb -N app show dev eth0 dscp-prio
dscp-prio 0:0 24:2 24:3 48:6
Reconfigure the table so that the only rule for DSCP 24 is for assign-
ment of priority 4:
# dcb app replace dev eth0 dscp-prio 24:4
# dcb app -N show dev eth0 dscp-prio
dscp-prio 0:0 24:4 48:6
Flush all DSCP rules:
# dcb app flush dev eth0 dscp-prio
# dcb app show dev eth0 dscp-prio
(nothing)
Add a rule to map traffic with PCP 1 and DEI 0 to priority 1 and PCP 2
and DEI 1 to priority 2:
# dcb app add dev eth0 pcp-prio 1nd:1 2de:2
# dcb app show dev eth0 pcp-prio
pcp-prio 1nd:1 2de:2
EXIT STATUS
Exit status is 0 if command was successful or a positive integer upon
failure.
SEE ALSO
dcb(8)
REPORTING BUGS
Report any bugs to the Network Developers mailing list <netdev@vger.ker-
nel.org> where the development and maintenance is primarily done. You
do not have to be subscribed to the list to send a message there.
AUTHOR
Petr Machata <me@pmachata.org>
iproute2 6 December 2020 DCB-APP(8)
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