Huawei S6700 Series Configuration Manual page 258

S6700 Series Ethernet Switches
Configuration Guide - IP Routing
LSP Fragment Extension
When more information is carried in an LSP to be advertised by IS-IS, IS-IS advertises multiple
LSP fragments. Each LSP fragment is identified by the LSP identifier field of an LSP. The LSP
identifier field is 1 byte long. Therefore, the maximum number of fragments that can be generated
by an IS-IS router is 256.
The IS-IS fragment extension feature allows an IS-IS router to generate more LSP fragments.
To implement this feature, you can use the network manager to configure additional system IDs
for the switch. Each system ID represents a virtual system, which can generate 256 LSP
fragments. With more additional system IDs (up to 50 virtual systems), an IS-IS router can
generate a maximum of 13056 LSP fragments.
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Dynamic Host Name Exchange Mechanism
The dynamic host name exchange mechanism is introduced to conveniently manage and
maintain IS-IS networks. The mechanism provides a service of mapping host names to system
IDs for the IS-IS routers. The dynamic host name information is advertised in the form of a
dynamic host name TLV in an LSP.
The dynamic host name exchange mechanism also provides a service to associate a host name
with the designated intermediate system (DIS) on a broadcast network. Then LSPs of pseudo
nodes advertise this association in the form of a dynamic host name TLV.
Issue 01 (2012-03-15)
Related terms are as follows:
– Originating system
In this document, the originating system is the switch that actually runs the IS-IS
protocol, and each IS-IS process is regraded as multiple virtual routers to generate LSP
fragments.
– Normal system ID
It is the system ID of the originating system.
– Additional System-ID
An additional system ID, assigned by the network administrator, represents a virtual
system. Each virtual system is allowed to generate up to 256 extended LSP fragments.
Like a normal system ID, an additional system ID must be unique in a routing domain.
– Virtual system
It is a virtual system for generating extended LSP fragments. Each virtual system has a
unique additional system ID, and each extended LSP fragment carries an additional
system ID.
Operating mode
An IS-IS router can run the LSP fragment extension feature in the following modes:
– Mode 1: The originating system sends a link to each virtual system. Then each virtual
system sends a link to the originating system. The virtual systems function as the
switchs that are connected to the originating system on the network. This mode is used
when some routers on the network do not support the LSP fragment extension feature.
In this mode, only the routing information can be advertised in the LSPs of the virtual
systems.
– Mode 2: All the switchs on the network can learn that the LSPs generated by the virtual
systems actually belong to the originating system. This mode is used when all the
switchs on the network support the LSP fragment extension feature. In this mode, all
link state information can be advertised in the LSPs of the virtual systems.
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