Switch 7700 Configuration Guide, v2

102 CHAPTER 5: ROUTING PROTOCOL OPERATION
and format identifier (AFI) and initial domain identifier (IDI). AFI defines the format
of IDI. DSP has several bytes.
Area Address is composed of routing field and area identifier. The routing field
includes AFI and IDI and may also includes the first byte of DSP. It identifies the
organization structure. It is followed by an area identifier of 16 bits.
The following 48 bits (or 6 bytes) of System ID identifies the host or router
uniquely. The router belonging to different areas has only one identifier.
NSAP Selector (SEL) of 8 bits does not select routes but equals the protocol
identifier of IP. Different transmission protocols correspond to different identifiers.
All the SELs of IP are 00.
AFI+IDI+HO-DSP+System ID composes the Network Entity Title, or NET for short,
which indicates the area address and system ID for routing. ID should be unique
inside the whole area and on the backbone (Level-2).
For example, there is a NET 47.0001.aaaa.bbbb.cccc.00, in which,
Area=47.0001, System ID=aaaa.bbbb.cccc, SEL=00.
For example, there is a NET 01.1111.2222.4444.00, in which,
Area=01, System ID=1111.2222.4444, and SEL=00.
IS-IS Routing Protocol
Packets
IS-IS packets are directly encapsulated in the data link frames and mainly divided
into 4 kinds, IIH, LSP,
CSNP, and PSNP.
■ Intermediate System to Intermediate System Hello PDU (IIH). It is transmitted
regularly to detect if the contiguous system is running IS-IS so as to establish
adjacency and switch Link State Protocol Data Unit (LSP), thereby implementing
LSDB synchronization.
■ Link State Protocol Data Unit (LSP). It is used for propagating link state records
throughout the area. LSP includes Level-1 LSP and Level-2 LSP.Level-2 LSP
contains the information about all the reachable areas. Level-1 LSP is only used
for local area.
■ Complete Sequence Numbers Protocol Data Unit (CSNP). CSNP includes Level-1
CSNP and Level-2 CSNP. CSNP is used for database synchronization. The DIS is
transmitted (every 10 seconds by default) regularly on the broadcast network.
Over the p2p serial line, the CSNP is transmitted only when the adjacent
relationship is established for the first time.
■ Partial Sequence Numbers Protocol Data Unit (PSNP). PSNP includes Level-1
PSNP and Level-2 PSNP.PSNP is also applied to the database synchronization.
Over the p2p link, the routers transmit PSNP as Ack response to acknowledge
the receipt of a certain LSP. The router requests the neighbor for the latest LSP.
If it finds the received CSNP missed some database (or the original database is
older), it will transmit PSNP for a new LSP.
For more information, refer to relevant documentation, such as ISO 10589.
Configuring Integrated
IS-IS
Among the following configuration tasks, enabling IS-IS is required, while other
tasks are optional.