Blade ICE G8124 Manuale Utente
BLADEOS 6.5.2 Application Guide
204
Chapter 14: FCoE and CEE
BMD00220, October 2010
Enhanced Transmission Selection
Enhanced Transmission Selection (ETS) is defined in IEEE 802.1Qaz. ETS provides a method for
allocating port bandwidth based on 802.1p priority values in the VLAN tag. Using ETS, different
amounts of link bandwidth can specified for different traffic types (such as for LAN, SAN, and
management).
allocating port bandwidth based on 802.1p priority values in the VLAN tag. Using ETS, different
amounts of link bandwidth can specified for different traffic types (such as for LAN, SAN, and
management).
ETS is an essential component in a CEE environment that carries different types of traffic, each of
which is sensitive to different handling criteria, such as Storage Area Networks (SANs) that are
sensitive to packet loss, and LAN applications that may be latency-sensitive. In a single converged
link, such as when implementing FCoE, ETS allows SAN and LAN traffic to coexist without
imposing contrary handling requirements upon each other.
which is sensitive to different handling criteria, such as Storage Area Networks (SANs) that are
sensitive to packet loss, and LAN applications that may be latency-sensitive. In a single converged
link, such as when implementing FCoE, ETS allows SAN and LAN traffic to coexist without
imposing contrary handling requirements upon each other.
The ETS feature requires CEE to be turned on (see
802.1p Priority Values
Under the 802.1p standard, there are eight available priority values, with values numbered 0
through 7, which can be placed in the priority field of the 802.1Q VLAN tag:
through 7, which can be placed in the priority field of the 802.1Q VLAN tag:
Servers and other network devices may be configured to assign different priority values to packets
belonging to different traffic types (such as SAN and LAN).
belonging to different traffic types (such as SAN and LAN).
ETS uses the assigned 802.1p priority values to identify different traffic types. The various priority
values are assigned to priority groups (PGID), and each priority group is assigned a portion of
available link bandwidth.
values are assigned to priority groups (PGID), and each priority group is assigned a portion of
available link bandwidth.
Priorities values within in any specific ETS priority group are expected to have similar traffic
handling requirements with respect to latency and loss.
handling requirements with respect to latency and loss.
16 bits
3 bits
1
12 bits
Tag Protocol ID (0x8100)
Priority CFI
VLAN ID
0
15 16
32