10 Facts About IS-IS

IS-IS is an interior gateway protocol, designed for use within an administrative domain or network.

IS-IS is a link-state routing protocol, operating by reliably flooding link state information throughout a network of routers.

IS-IS protocol was developed by a team of people working at Digital Equipment Corporation as part of DECnet Phase V It was standardized by the ISO in 1992 as ISO 10589 for communication between network devices that are termed Intermediate Systems by the ISO.

The purpose of IS-IS was to make possible the routing of datagrams using the ISO-developed OSI protocol stack called CLNS.

IS-IS was developed at roughly the same time that the Internet Engineering Task Force IETF was developing a similar protocol called OSPF.

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IS-IS was later extended to support routing of datagrams in the Internet Protocol, the Network Layer protocol of the global Internet.

IS-IS is an OSI Layer 3 protocol initially defined for routing CLNS.

However, IS-IS is easier to expand: its use of TLV data allows engineers to implement support for new techniques without redesigning the protocol.

For example, in order to support IPv6, the IS-IS protocol was extended to support a few additional TLVs, whereas OSPF required a new protocol draft.

IS-IS is therefore augmented with a small number of TLVs and sub-TLVs, and supports two Ethernet encapsulating data paths, 802.