Skip to main content
Sign Out

Welcome to Dell

My Account
  • Place orders quickly and easily
  • View orders and track your shipping status
  • Create and access a list of your products
  • Manage your Dell EMC sites, products, and product-level contacts using Company Administration.
Sign In Create an Account Premier Sign In Partner Program Sign In
Contact Us

Dell PowerEdge FN I/O Module Configuration Guide 9.10(0.0)

PDF

Enhanced Transmission Selection

Enhanced transmission selection (ETS) supports optimized bandwidth allocation between traffic types in multiprotocol (Ethernet, FCoE, SCSI) links.

ETS allows you to divide traffic according to its 802.1p priority into different priority groups (traffic classes) and configure bandwidth allocation and queue scheduling for each group to ensure that each traffic type is correctly prioritized and receives its required bandwidth. For example, you can prioritize low-latency storage or server cluster traffic in a traffic class to receive more bandwidth and restrict best-effort LAN traffic assigned to a different traffic class.

Although you can configure strict-priority queue scheduling for a priority group, ETS introduces flexibility that allows the bandwidth allocated to each priority group to be dynamically managed according to the amount of LAN, storage, and server traffic in a flow. Unused bandwidth is dynamically allocated to prioritized priority groups. Traffic is queued according to its 802.1p priority assignment, while flexible bandwidth allocation and the configured queue-scheduling for a priority group is supported.

The following figure shows how ETS allows you to allocate bandwidth when different traffic types are classed according to 802.1p priority and mapped to priority groups.

Figure 1. Enhanced Transmission Selection Illustration of enhanced transmission selection.

The following table lists the traffic groupings ETS uses to select multiprotocol traffic for transmission.

Table 1. ETS Traffic Groupings
Traffic GroupingsDescription
Priority groupA group of 802.1p priorities used for bandwidth allocation and queue scheduling. All 802.1p priority traffic in a group must have the same traffic handling requirements for latency and frame loss.
Group IDA 4-bit identifier assigned to each priority group. The range is from 0 to 7.
Group bandwidthPercentage of available bandwidth allocated to a priority group.
Group transmission selection algorithm (TSA)Type of queue scheduling a priority group uses.
In the Dell Networking OS, ETS is implemented as follows:
  • ETS supports groups of 802.1p priorities that have:
    • PFC enabled or disabled
    • No bandwidth limit or no ETS processing
  • Bandwidth allocated by the ETS algorithm is made available after strict-priority groups are serviced. If a priority group does not use its allocated bandwidth, the unused bandwidth is made available to other priority groups so that the sum of the bandwidth use is 100%. If priority group bandwidth use exceeds 100%, all configured priority group bandwidth is decremented based on the configured percentage ratio until all priority group bandwidth use is 100%. If priority group bandwidth usage is less than or equal to 100% and any default priority groups exist, a minimum of 1% bandwidth use is assigned by decreasing 1% of bandwidth from the other priority groups until priority group bandwidth use is 100%.
  • For ETS traffic selection, an algorithm is applied to priority groups using:
    • Strict priority shaping
    • ETS shaping
    • (Credit-based shaping is not supported)
  • ETS uses the DCB MIB IEEE 802.1azd2.5.

Rate this content

Accurate
Useful
Easy to understand
Was this article helpful?
0/3000 characters
  Please provide ratings (1-5 stars).
  Please provide ratings (1-5 stars).
  Please provide ratings (1-5 stars).
  Please select whether the article was helpful or not.
  Comments cannot contain these special characters: <>()\