Figure 6-1 Layer 2 Diagram (802.1Q) - NEC SL1100 Networking Manual

NEC SL1100
Networking Manual
using layer 2 classes of service (CoS) settings in the User Priority bits of
the 802.1Pq header. Refer to Program
5-30 for information for VLAN configuration.
PREAM SFD DA
Three bits used for CoS
(user priority)

Figure 6-1 Layer 2 Diagram (802.1Q)

IP Precedence - Layer 3 QoS:

Allows you to specify the class of service for a packet. You use the three
precedence bits in the IPv4 header type of service (ToS) field for this
purpose. Using the ToS bits, you can define up to six classes of service.
Other devices configured throughout the network can then use these bits
to determine how to treat the packet in regard to the type of service to
grant it. These other QoS features can assign appropriate
traffic-handling policies including congestion management and
bandwidth allocation. By setting IP Precedence levels on incoming traffic
and using them in combination with QoS queuing features, you can
create differentiated service. (Refer to Program
page 5-31 for detailed programming information.)
Differentiated service (Diffserv) - Layer 3 QoS:

Provides services differentiated on performance using weighted priority
queuing. DiffServ requires that edge routers classify traffic flows into a
member from a set of categories based on the TCP/IP header fields in
what is called a micro flow. Because the Diffserv is present in every
packet header, each node can provide differentiated services per-hop.
Refer to Program
programming information.
Layer 2
802.1Q/p
TAG
SA PT
Type
4 Bytes
CFI VLAN ID
PRI
84-10 : ToS Setup on page 5-31
84-09 : VLAN Setup on page
Data
84-10 : ToS Setup on
for detailed
Issue 6.0
FCS
6 - 5