Manual: dcb-app
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 assign priority to traffic based on value in one of several headers: EtherType, L4 destina‐
tion port, or DSCP. It also allows configuration of port-default priority that is chosen if no other prioritization
rule applies.
DCB APP entries are 3-tuples of selector, protocol ID, and priority. Selector is an enumeration that picks one of the
prioritization namespaces. Currently it mostly corresponds to configurable parameters described 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 se‐
lector 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 conflicting priority assignment for the same selector and protocol ID. For example, 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 indi‐
vidual APP 3-tuples through add and del commands. On the other hand, the command replace does what one would typi‐
cally want in this situation--first adds the new configuration, 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 entries, whose selector and protocol ID have been mentioned as parameter, but not with the exact
same priority. This has the effect of, for the given selector and protocol ID, causing that the table only
contains the priority (or priorities) given as parameter.
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 otherwise unspecified. The argument is a list of
individual priorities. Note that default-prio rules are configured as triplets (EtherType, 0, PRIO). dcb app
translates these rules to the symbolic 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 priori‐
ties 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 traffic.
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 as‐
signed 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 assignment 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 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
iproute2 6 December 2020 DCB-APP(8)