High-speed WAN digital communication protocol that operates at a rate of 34.368 Mbps and uses time-division multiplexing to carry 16 E1 circuits.

early packet discard

See EPD.


External BGP. A BGP configuration in which sessions are established between routers in different autonomous systems (ASs).


The E-carrier system, where 'E' stands for European, is incompatible with the T-carrier system and is used just about everywhere in the world except North America and Japan. It typically uses the E1 and the E3 line rates.


Error checking and correction. The process of detecting errors during the transmission or storage of digital data and correcting them automatically. This usually involves sending or storing extra bits of data according to specified algorithms.


Exchange Carriers Standards Association. A standards organization created after the divestiture of the Bell System to represent the interests of interexchange carriers.

edge router

In MPLS, a router located at the beginning or end of a label-switching tunnel. When at the beginning of a tunnel, an edge router applies labels to new packets entering the tunnel. When at the end of a tunnel, the edge router removes labels from packets exiting the tunnel. See also MPLS.

editor macros (Emacs)

Shortcut keystrokes used within the router's command-line interface (CLI). These macros move the cursor and delete characters based on the specific sequence you specify.


Exterior gateway protocol; for example, BGP.

egress router

In MPLS, the last router in a label-switched path (LSP). See also ingress router.


Electronic Industries Association. A United States trade group that represents manufacturers of electronics devices and sets standards and specifications.


Serial interface that employs the EIA-530 standard for the interconnection of DTE and DCE equipment.


Equipment identity register. A mobile network database that contains information about devices using the network.

electromagnetic interference

See EMI.

electrostatic discharge

See ESD.

embedded OS software

Software used by a Juniper Networks router to operate the physical router components.


Electromagnetic interference. Any electromagnetic disturbance that interrupts, obstructs, or otherwise degrades or limits the effective performance of electronics or electrical equipment.

Encapsulating Security Payload

See ESP.

end system

In IS-IS, a network entity that sends and receives packets.


Early packet discard. For ATM2 interfaces only, a limit on the number of transmit packets that can be queued. Packets that exceed the limit are dropped. See also queue length.


Explicit Route Object. An extension to RSVP that allows an RSVP PATH message to traverse an explicit sequence of routers that is independent of conventional shortest-path IP routing.

error checking and correction

See ECC.


Electrostatic discharge. Stored static electricity that can damage electronic equipment and impair electrical circuitry when released.


End System-to-Intermediate System. Protocol that resolves Layer 3 ISO network service access points (NSAPs) to Layer 2 addresses. ES-IS resolution is similar to the way ARP resolves Layer 2 addresses for IPv4.


Encapsulating Security Payload. A protocol for securing packet flows for IPSec using encryption, data integrity checks, and sender authentication, which are added as a header to an IP packet. If an ESP packet is successfully decrypted, and no other party knows the secret key the peers share, the packet was not wiretapped in transit. See also AH.


BGP neighbor state that represents a fully functional BGP peering session.


Local area network (LAN) technology used for transporting information from one location to another, formalized in the IEEE standard 802.3. Ethernet uses either coaxial cable or twisted-pair cable. Transmission speeds for data transfer vary from the original 10 Mbps, to Fast Ethernet at 100 Mbps, to Gigabit Ethernet at 1000 Mbps.


European Telecommunications Standardization Institute. A nonprofit organization that produces voluntary telecommunications standards used throughout Europe.

European Telecommunications Standardization Institute



JUNOS software routing policy match type that represents only the route specified in a route filter.

exception packet

IP packet that is not processed by the normal packet flow through the Packet Forwarding Engine. Exception packets include local delivery information, expired TTL packets, or packets with an IP option specified.


OSPF adjacency state in which the two neighboring routers are actively sending database description packets to each other to exchange their database contents.

exclusive or

See XOR.

EXP bits

Experimental bits, also known as the class-of-service (CoS) bits, located in each MPLS label and used to encode the CoS value of a packet as it traverses an LSP.

explicit path

See signaled path.

Explicit Route Object

See ERO.


Placing of routes from the routing table into a routing protocol.


OSPF adjacency state where the neighboring routers negotiate which router is in charge of the synchronization process.

Extensible Markup Language

See XML.

Extensible Stylesheet Language for Transformations


exterior gateway protocol

See EGP.

external BGP


external metric

Cost included in a route when OSPF exports route information from external autonomous systems. There are two types of external metrics: Type 1 and Type 2. Type 1 external metrics are equivalent to the link-state metric; that is, the cost of the route, used in the internal autonomous system. Type 2 external metrics are greater than the cost of any path internal to the autonomous system.