Cisco Systems C3850NM410G Cisco Catalyst 3850 Quality of Service

The total capacity of the ACEs is an aggregate number that constitutes all types of ACEs. One type of ACE,

however, can scale up to 1500. For example, the total number of Port ACL (PACL) access control entries cannot

exceed 1500. But a combination of PACL and Router ACL (RACL) access control entries can scale up to 3000.

Cisco Catalyst 3850 Quality of Service

One of the primary advantages of the Cisco Catalyst 3850 is the visibility into wireless packets at the access layer.

This visibility is a powerful feature and enables network administrators to apply the rich intelligent services of wired

traffic and extend these services to wireless traffic as well. QoS is one of the features that can be applied on

wireless traffic similar to that of being applied on wired network.

Significant QoS features have been introduced for wired as well as wireless on the Cisco Catalyst 3850. Some of

them are the following and are discussed in detail later in the document:

● Modular QoS CLI (MQC)

● Approximate Fair-Drop (AFD) algorithm for bandwidth management across wireless users, providing

hierarchical support across access points, radios, Basic Service Set Identifier (BSSID), and clients.

● Eight queues per port (wired) and 4 queues per port (wireless)

● Bidirectional policing support in hardware for wireless clients

● Two-level hierarchical QoS on wired ports

● Per-SSID bandwidth management; differentiated bandwidth management across SSIDs

Because of the inherent differences of wired and wireless media and transmission methods, there are differences

between wired and wireless QoS.

Wired QoS on the Cisco Catalyst 3850 is explained later, followed by wireless QoS in the following section.

Cisco Catalyst 3850 Trust Behavior

The trust behavior on the Cisco Catalyst 3850 has changed from the that of Cisco Catalyst 3K Series switches. By

default, the Cisco Catalyst 3850 trusts markings on the wired ports. For wired ports, differentiated services code

point (DSCP) markings in IP packets from endpoints such as IP phones, telepresence units, cameras, and laptops

are trusted and retained.

Retained markings are summarized in Table 2.

Table 2. Trust Behavior

Incoming Packet

Outgoing Packet

Trust Behavior

Preserve DSCP/precedence

Not applicable

Tagged

Preserve DSCP and class of service (CoS)

Tagged

Preserve DSCP; CoS is set to 0

With the introduction of MQC, the “trust cos/dscp” CLI has been deprecated on the Cisco Catalyst 3850. However,

“trust device” on the interface level is still supported. The default mode on the interface is trusted and changes to

untrusted only when an untrusted device is detected. In the untrusted mode, the DSCP/precedence/CoS will be

reset to 0.