CLNS Terms
Before configuring CLNS, become familiar with the terms defined in Table 201.
Table 201: CLNS Terms
Term | Definition |
|---|---|
CLNS island | Typically one IS-IS level 1 area that is part of a single IGP routing domain. An island can contain more than one area. CLNS islands can be connected by virtual private networks (VPNs). |
Connectionless Network Service (CLNS) | Layer 3 protocol similar to IPv4 for linking hosts (end systems) with routers (intermediate systems) in an Open Systems Interconnection (OSI) network, by using network service access points (NSAPs) instead of prefix addresses to specify hosts and routers. |
customer edge (CE) router | Router or switch in the customer's network that is connected to a service provider's provider edge (PE) router and participates in a Layer 3 VPN. |
end system | A host in an Open Systems Interconnection (OSI) network. |
End System-to-Intermediate System (ES-IS) | Protocol that enables end systems (hosts) and intermediate systems (routers) to discover each other, by a method similar to Address Resolution Protocol (ARP) discovery in an IPv4 network. |
intermediate system | A router in an Open Systems Interconnection (OSI) network. |
International Organization for Standardization (ISO) | Worldwide federation of standards bodies that promotes international standardization and published international agreements as International Standards. |
network layer reachability information (NLRI) | Information about routes exchanged in update messages by Border Gateway Protocol (BGP) systems, to enable routers to determine the relationships among all known BGP autonomous systems. |
network services access point (NSAP) | International Standards Organization (ISO) addressing method for identifying hosts (end systems) and routers (intermediate systems) at the data-link layer (Layer 3) in an Open Systems Interconnection (OSI) network. An NSAP is from 8 to 20 bytes long and consists of an area address, a system ID, and an NSAP selector (NSEL) byte. |
Open Systems Interconnection (OSI) | Standard reference model for representing the way messages are transmitted between two points on a network. |
provider edge (PE) router | Services Router in the service provider network that is connected to a customer edge (CE) router and participates in a virtual private network (VPN). |
virtual private network (VPN) | Private data network that uses a public TCP/IP network, typically the Internet, while maintaining privacy with a tunneling protocol, encryption, and security procedures. |