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II. Introduction to NTDP
NTDP is a protocol used to collect network topology information. NTDP provides
information required for cluster management: it collects topology information about the
switches within the specified hop count, so as to provide the information of which
devices can be added to a cluster.
Based on the neighbor information stored in the neighbor table maintained by NDP,
NTDP on the management device advertises NTDP topology collection requests to
collect the NDP information of each device in a specific network range as well as the
connection information of all its neighbors. The information collected will be used by the
management device or the network management software to implement required
functions.
When a member device detects a change on its neighbors through its NDP table, it
informs the management device through handshake packets, and the management
device triggers its NTDP to perform specific topology collection, so that its NTDP can
discover topology changes timely.
The management device collects the topology information periodically. You can also
launch an operation of topology information collection by executing related commands.
The process of topology information collection is as follows.
z The management device sends NTDP topology collection requests periodically
through its NTDP-enabled ports.
z Upon receiving an NTDP topology collection request, the device returns a NTDP
topology collection response to the management device and forwards the request
to its neighbor devices through its NTDP-enable ports. The topology collection
response packet contains the information about the local device and the NDP
information about all the neighbor devices.
z The neighbor devices perform the same operation until the NTDP topology
collection request is propagated to all the devices within the specified hops.
When an NTDP topology collection request is propagated in the network, it is received
and forwarded by large numbers of network devices, which may cause network
congestion and the management device busy processing of the NTDP topology
collection responses. To avoid such cases, the following methods can be used to
control the NTDP topology collection request advertisement speed.
z Configuring the devices not to forward the NTDP topology collection request
immediately after they receive an NTDP topology collection request. That is,
configure the devices to wait for a period before they forward the NTDP topology
collection request.
z Configuring each NTDP-enabled port on a device to forward an NTDP topology
collection request after a specific period since the previous port on the device
forwards the NTDP topology collection request.
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