About Dcbxp - Cisco Nexus 7000 Series Configuration Manual

About DCBXP

To permit the discovery of non-Cisco devices, the switch also supports the Link Layer Discovery Protocol
(LLDP), a vendor-neutral device discovery protocol that is defined in the IEEE 802.1ab standard. LLDP
allows network devices to advertise information about themselves to other devices on the network. This
protocol runs over the data-link layer, which allows two systems running different network layer protocols
to learn about each other.
LLDP is a one-way protocol that transmits information about the capabilities and current status of a device
and its interfaces. LLDP devices use the protocol to solicit information only from other LLDP devices.
LLDP supports a set of attributes that it uses to discover other devices. These attributes contain type, length,
and value (TLV) descriptions. LLDP devices can use TLVs to send and receive information to other devices
on the network. Details such as configuration information, device capabilities, and device identity can be
advertised using this protocol.
LLDP advertises the following TLVs by default:
• DCBXP
• Management address
• Port description
• Port VLAN
• System capabilities
• System description
• System name
About DCBXP
The Data Center Bridging Exchange Protocol (DCBXP) is an extension of LLDP. It is used to announce,
exchange, and negotiate node parameters between peers. DCBXP parameters are packaged into a specific
DCBXP TLV. This TLV is designed to provide an acknowledgement to the received LLDP packet. In this
way, DCBXP adds a lightweight acknowledgement mechanism on top of LLDP so that any application that
needs a request-response semantic from a link-level protocol can make use of DCBXP.
Other applications that need to exchange and negotiate parameters with peer nodes using DCBXP are as
follows:
• Priority-based Flow Control (PFC)—PFC is an enhancement to the existing Pause mechanism in Ethernet.
• Enhanced Transmission Selection (ETS)—ETS enables optimal bandwidth management of virtual links.
• Application Priority Configuration TLV—Carries information about which VLANs will be used by
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It enables Pause based on user priorities or classes of service. A physical link divided into eight virtual
links with PFC provides the capability to use Pause on a single virtual link without affecting traffic on
the other virtual links. Enabling Pause on a per-user-priority basis allows administrators to create lossless
links for traffic requiring no-drop service while retaining packet-drop congestion management for IP
traffic.
ETS is also called priority grouping. It enables differentiated treatments within the same priority classes
of PFC. ETS provides prioritized processing based on bandwidth allocation, low latency, or best effort,
resulting in per-group traffic class allocation. For example, an Ethernet class of traffic may have a
high-priority designation and a best effort within that same class. ETS allows differentiation between
traffic of the same priority class, thus creating priority groups.
specific protocols.
Configuring LLDP