Updates packet marking api documentation to traffic manager user guide Signed-off-by: Balasubramanian Manoharan <[email protected]> --- v2: document format update doc/users-guide/users-guide-tm.adoc | 73 +++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+)
diff --git a/doc/users-guide/users-guide-tm.adoc b/doc/users-guide/users-guide-tm.adoc index 12685b2..e02697b 100644 --- a/doc/users-guide/users-guide-tm.adoc +++ b/doc/users-guide/users-guide-tm.adoc @@ -263,6 +263,79 @@ settings for any TM system, though in most cases a TM system can (and should) be created/instantiated with smaller values, since lower values will often result in faster operation and/or less memory used. +==== Packet Marking + +The Packet Marking API is used to mark the packet based upon the final packet +color assigned to it when it reaches the egress node. +This is an optional feature and if available on the platform is used to reflect +the packet color on IPv4/IPv6 DiffServ filed in accordance with https://www.ietf.org/rfc/rfc2474.txt[RFC 2474]. +There are three different packet marking fields supported they are, +1). Assured forwarding in accordance with https://www.ietf.org/rfc/rfc2597.txt[RFC 2597], the DSCP is marked to +set the packet Drop precedence in accordance with the color, i.e High Drop +precedence for RED, Medium Drop precedence for YELLOW and leave the DSCP +unchanged if the color is GREEN. +2). Explicit Congestion Notification protocol per https://www.ietf.org/rfc/rfc3168.txt[RFC 3168], where a router +encountering congestion can notify it by setting the lower 2 bits in +DiffServ field to "11" Congestion Encountered code, which will ultimately +reduce the transmission rate of the packet sender. +3). In IEEE 802.1q VLAN tag header contains a DE - Drop Eligibility bit for +marking a packet for Downstream switches, and is valid for Ethernet packet +containing a VLAN tag. + +RFC 3168 is only valid for TCP packets whereas RFC 2597 is valid for IPv4/IPv6 +traffic. + +The values are set per color and hence the implementation may support these +parameters only for a specific colors. marking_colors_supported field in +capabilities structure can be used to check which colors are supported for +marking. + +==== Vlan Marking. + +This vlan marking is used to enable the drop eligibility on the packet +based on the packet color. If drop eligibility is enabled then the +implementation will set the one bit VLAN Drop Eligibility Indicator (DEI) +field (but only for packets that already carry a VLAN tag) of a packet based +upon the final packet color assigned to the packet when it reaches the egress +node. When drop_eligible_enabled is false, then the given color has +no effect on the VLAN fields. See IEEE 802.1q for more details. +`vlan_marking_supported` boolean in capability structure indicates whether this +feature is supported by the implementation. + +==== Explicit Congestion Notification Marking. + +The `odp_tm_ecn_marking()` function allows one to configure the TM +egress so that the two bit ECN subfield of the eight bit TOS field of an +IPv4 packet OR the eight bit Traffic Class (TC) field of an IPv6 packet can be +selectively modified based upon the final color assigned to the packet when it +reaches the egress. Note that the IPv4 header checksum will be updated - +but only if the IPv4 TOS field actually changes as a result of this +setting or the `odp_tm_drop_prec_marking()` setting. For IPv6, since there is +no header checksum, nothing needs to be done. If ECN is enabled for a +particular color then ECN subfield will be set to _ECN_CE_ _i.e.,_ congestion +experienced. +`ecn_marking_supported` boolean in capability structure indicates whether this +feature is supported by the implementation. + +==== Drop Precedence Marking. + +The Drop precedence marking allows one to configure the TM +egress to support Assured forwarding in accordance with https://www.ietf.org/rfc/rfc2597.txt[RFC 2597]. +The Drop Precedence bits are contained within the six bit Differentiated +Services Code Point subfield of the IPv4 TOS field or the IPv6 Traffic +Class (TC) field. Specifically the Drop Precedence sub-subfield can be +accessed with a DSCP bit mask of 0x06. When enabled for a given color, +these two bits will be set to Medium Drop Precedence (value 0x4) if the +color is ODP_PACKET_YELLOW, set to High Drop Precedence (value 0x6) if +the color is ODP_PACKET_RED. + +Note that the IPv4 header checksum will be updated - but only if the +IPv4 TOS field actually changes as a result of this setting or the +`odp_tm_ecn_marking()` setting. For IPv6, since there is no header checksum, +nothing else needs to be done. +`drop_prec_marking_supported` boolean in capability structure indicates whether +this feature is supported by the implementation. + === Examples .Create a tm_node chain for two nodes and associate the scheduler -- 1.9.1 _______________________________________________ lng-odp mailing list [email protected] https://lists.linaro.org/mailman/listinfo/lng-odp
