Ericsson MINI-LINK PT 2010 ETSI Technical Description page 31

Note: IEEE 802.3x-based congestion handling mechanism does not take into
6.2.1 Class of Service
The Class of Service (CoS) value for a frame is a representation of the end
user services, such as voice and best effort data. The CoS value is set in
the priority bits in the Ethernet header and is typically defined at the network
edge. The priority bits are set based on whether the port is trusted or not.
The following options are supported:
•
•
•
•
The defined CoS value is stored in the PCP value in the Q-tag in the Ethernet
header and is used throughout the network.
The WAN (radio side) Ethernet egress port can be configured with 1–8 Traffic
Classes (TCs), where 8 TCs are default.
The CoS priority information is used to map the Ethernet frames into the
1–8 TCs. The mapping can be done according to either IEEE802.1D-2004,
IEEE802.1Q-2005 or custom. Frames with no CoS information are mapped to
the default traffic class (TC0).
There are individual queues for each CoS. The Ethernet frames in the egress
queues are either scheduled according to a strict priority scheme.
6.2.2 Tail Dropping
All new packets that are scheduled to a CoS queue that is already full are
dropped regardless of priority.
6.2.3 Packet Aging
It is possible to drop packets based on age. When Packet Aging is used,
packets that have been stored too long and no longer can be delivered with
purpose are dropped. Packet aging is configured per service per TC, where a
service is the switch or one of the Ethernet Layer 1 Connection services. The
default settings for Ethernet packet aging is shown in Figure 17.
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account the usage of different priority levels. The reception of a PAUSE
message triggers a network element to halt all Ethernet frames. This
means that IEEE 802.3x-based congestion handling is not suitable for
networks configured for different priority levels and transmission of
real-time traffic.
IP TOS/DSCP for IPv4 or IPv6
Reuse Priority Code Point (PCP) value in C-tag (Q-tag, VLAN) or S-tag
User defined value
EXP bits in MPLS header
MINI-LINK PT 2010 Functions – Ethernet
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