IS-IS Acronyms
Term Acronym Description
Circuit ID Identifies a physical interface on
the router.
Complete Sequence CSNP A summary of a router’s
Number PDU complete LSDB.
Connectionless CLNP OSI protocol used to provide the
Network Protocol connectionless services.
Connectionless CNLS OSI data delivery service that
Network Services provides best-effort delivery.
End System ES A host, such as a computer.
Intermediate System IS The OSI name for a router.
Intermediate System hello ISH Sent by routers to hosts.
IS to IS hello IIH Hellos exchanged between
routers. Seperate level 1 and
level 2 IIHs exist.
Link State Database LSDB A database containing all the
LSAs the router knows about,
and it keeps a separate LSDB
for each area it belongs to.
Link State PDU LSP A routing update.
Network Entity Title NET A router’s NSAP. The last byte
of a NET is always zero.
continues
Table 4-1 IS-IS Acronyms continued
Term Acronym Description
Network Service NSAP Address of a CLNS device.
Access Point Addresses are assigned per
device, not per interface
as with IP.
NSAP Selector NSEL The last byte of a NSAP
address. Identifies the process
on the device, such as routing.
Protocol Data Unit PDU A unit of data.
Partial Route Calculation PRC Used to determine end system
and IP subnet reachability.
Partial Sequence Number PSNP Used to acknowledge receipt of
PDU a CSNP and to request more
information about a network
contained in a CSNP.
Sequence Number Protocol SNP An IS-IS packet that is Data
Unit sequenced and must be
acknowledged. The sequence
number helps a router maintain
the most recent link state
information.
Subnetwork Point SNPA Layer 2 identification for a of
Attachment router’s interface, such as MAC
address or DLCI.
Type Length Value TLV Fields in the IS-IS updates
that contain IP subnet,
authentication, and end-system
information.