Precision Time Protocol. Packet-based technology that enables an operator to deliver synchronization services on packet-based mobile backhaul networks. PTP is a highly precise protocol for time synchronization that synchronizes clocks in a distributed system. The time synchronization is achieved through packets that are transmitted and received in a session between a primary clock and a client clock. Also known as IEEE 1588v2. See also primary clock, client clock.

link aggregation group. Two or more network links bundled together to function as a single link. Distributes MAC clients across the Link Layer interface and collects traffic from the links to present to the MAC clients of the LAG. Also known as LAG bundle, 802.3ad link aggregation, EtherChannel.

Type of firewall created by a filter that evaluates the context of connections, permits or denies traffic based on the context, and updates this information dynamically. Context includes IP source and destination addresses, port numbers, TCP sequencing information, and TCP connection flags. The context established in the first packet of a TCP session must match the context contained in all subsequent packets if a session is to remain active. See also stateful firewall filter, stateless firewall filter.

Network Address Translation. Method of concealing a set of host addresses on a private network behind a pool of public addresses. Using NAT allows conservation of registered IP addresses within private networks, simplifies IP address management through a form of transparent routing, and increases network privacy by hiding internal IP addresses from external networks. It can be used as a security measure to protect the host addresses from direct targeting in network attacks. Also known as Network Address Translator. See also bidirectional NAT, traditional NAT, twice NAT.

intrusion detection service. Inspects all inbound and outbound network activity and identifies suspicious patterns that might indicate a network or system attack from someone attempting to break into or compromise a system.

Internet Protocol Security. Provides security to IP flows through the use of authentication and encryption:

• Authentication verifies that data is not altered during transmission and ensures that users are communicating with the individual or organization that they believe they are communicating with.
• Encryption makes data confidential by making it unreadable to everyone except the sender and intended recipient.

Physical Interface Card. Network interface–specific card that can be installed on an FPC in the router. Also known as card, blade, module.

Access Node Control Protocol. Based on a subset of the General Switch Management Protocol (GSMP) in which IGMP is no longer terminated or proxied at the access node. Instead, IGMP passes through the access node transparently. Also known as Layer 2 control (L2C).

Internet Group Management Protocol. Host-to-router signaling protocol for IPv4 to report multicast group memberships to neighboring routers and determine whether group members are present during IP multicasting. Similarly, multicast routers, such as E Series routers, use IGMP to discover which of their hosts belong to multicast groups and to determine whether group members are present.

• initial domain part. Portion of a CLNS address that consists of the AFI and IDI. See also AFI, IDI.
• Intrusion Detection and Prevention. Name of a Juniper Networks product line of security devices that run the IDP OS (operating system).

Remote Authentication Dial-In User Service. Distributed client/server AAA service method that protects networks against unauthorized access. RADIUS clients running on an E Series router send authentication requests to a central RADIUS server. The central RADIUS server stores all the required user authentication and network access information. RADIUS informs the router of the privilege levels for which RADIUS-authenticated users have enable access. The router permits or denies enable access accordingly.

Dynamic Host Configuration Protocol. Mechanism through which hosts using TCP/IP can obtain protocol configuration parameters automatically from a DHCP server on the network; allocates IP addresses dynamically so that they can be reused when no longer needed.

bootstrap protocol. UDP/IP-based protocol that allows a booting host to configure itself dynamically and without user supervision. BOOTP provides a means to notify a host of its assigned IP address, the IP address of a boot server host, and the name of a file to be loaded into memory and executed. Other configuration information, such as the local subnet mask, the local time offset, the addresses of default routers, and the addresses of various Internet servers, can also be communicated to a host using BOOTP.

Point-to-Point Protocol. Link-layer protocol that provides multiprotocol encapsulation. PPP is used for Link Layer and Network Layer configuration. Provides a standard method for transporting multiprotocol datagrams over point-to-point links. Defined in RFC 1661, The Point-to-Point Protocol (PPP).

Operation, Administration, and Maintenance. ATM Forum specification for monitoring ATM virtual connections, verifying that the connection is up and that the router is operational. A set of Ethernet connectivity specifications and functions providing connectivity monitoring, fault detection and notification, fault verification, fault isolation, loopback, and remote defect identification. The primary specifications defining Ethernet OAM are IEEE 902.3ah link-fault management (LFM) and IEEE 902.1ag Ethernet connectivity-fault management (CFM). See also CFM, LFM.

class of service. Method of classifying traffic on a packet-by-packet basis using information in the type-of-service (ToS) byte to provide different service levels to different traffic. See also QoS.

Transmission Control Protocol. Works in conjunction with the Internet Protocol (IP) to send data over the Internet, creating connections between hosts for the exchange of data. Divides a message into packets and tracks the packets from point of origin to destination. Guarantees that packets are transmitted in their original sequence from sender to receiver.

User Datagram Protocol. In TCP/IP, a connectionless Transport Layer protocol that exchanges datagrams without acknowledgments or guaranteed delivery, requiring that error processing and retransmission be handled by other protocols.

dynamic flow capture. Process of collecting packet flows that match a particular filter list to one or more content destinations using an on-demand control protocol that relays requests from one or more control sources.

error checking and correction, error-checking code. 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.

connectivity fault management. End-to-end per-service-instance Ethernet layer operation, administration, and management (OAM) protocol. CFM includes proactive connectivity monitoring, fault verification, and fault isolation for large Ethernet metropolitan-area networks.

Operation, Administration, and Maintenance. ATM Forum specification for monitoring ATM virtual connections, verifying that the connection is up and that the router is operational. A set of Ethernet connectivity specifications and functions providing connectivity monitoring, fault detection and notification, fault verification, fault isolation, loopback, and remote defect identification. The primary specifications defining Ethernet OAM are IEEE 902.3ah link-fault management (LFM) and IEEE 902.1ag Ethernet connectivity-fault management (CFM). See also CFM, LFM.

link fault management. Method used to detect problems on links and spans on an Ethernet network defined in IEEE 802.3ah. See also OAM.

Inter-Chassis Control Protocol. Protocol that enables MC-LAG peers to exchange control information and coordinate with each other to ensure that data traffic is forwarded properly. See also MC-LAG.

• initial domain part. Portion of a CLNS address that consists of the AFI and IDI. See also AFI, IDI.
• Intrusion Detection and Prevention. Name of a Juniper Networks product line of security devices that run the IDP OS (operating system).

Asynchronous Transfer Mode. A high-speed multiplexing and switching method utilizing fixed-length cells of 53 octets to support multiple types of traffic.

graceful Routing Engine switchover. In a router that contains a primary and a backup Routing Engine, allows the backup Routing Engine to assume the primary role automatically, with no disruption of packet forwarding. Also known as Stateful Switchover (SSO).

• media access control (address). A unique code assigned to every piece of hardware that connects to the network. In the OSI seven-layer networking model defined by the IEEE, MAC is the lower sublayer of the Data Link Layer. The MAC sublayer governs protocol access to the physical network medium. By using the MAC addresses that are assigned to all ports on a router, multiple devices on the same physical link can uniquely identify one another at the Data Link Layer. See also MAC address.
• Message Authentication Code. In cryptography, a short piece of information used to authenticate a message. A MAC algorithm accepts as input a secret key and an arbitrary-length message to be authenticated, and outputs a MAC, or a tag. Sometimes called message integrity code (MIC) to distinguish the MAC function from the MAC (media access control) address.

link aggregation group. Two or more network links bundled together to function as a single link. Distributes MAC clients across the Link Layer interface and collects traffic from the links to present to the MAC clients of the LAG. Also known as LAG bundle, 802.3ad link aggregation, EtherChannel.

Management Information Base. Definition of an object that can be managed by SNMP.

Network File System. A protocol that allows a user on a client computer to access files over a network similarly to how local storage is accessed by providing transparent remote access to shared files across networks. It is a standard defined in several RFCs, first appearing in RFC 1094, NFS: Network File System Protocol Specification.

Label Distribution Protocol. A protocol for distributing labels in non-traffic-engineered applications. LDP allows routers to establish label-switched paths (LSPs) through a network by mapping Network Layer routing information directly to Data Link Layer switched paths.

virtual local area network. Logical group of network devices that appear to be on the same LAN, regardless of their physical location. VLANs are configured as unique Layer 2 broadcast domains consisting of logical, rather than physical, connections, making them extremely flexible. VLANs allow network administrators to resegment their networks without physically rearranging the devices or network connections. VLANs span one or more ports on multiple devices. By default, each VLAN maintains its own Layer 2 forwarding database containing MAC addresses learned from packets received on ports belonging to the VLAN. See also bridge domain.

Domain Name System. A system that stores information about hostnames and domain names. It provides an IP address for each hostname and lists the e-mail exchange servers accepting e-mail addresses for each domain.

Network File System. A protocol that allows a user on a client computer to access files over a network similarly to how local storage is accessed by providing transparent remote access to shared files across networks. It is a standard defined in several RFCs, first appearing in RFC 1094, NFS: Network File System Protocol Specification.

Point-to-Point Protocol. Link-layer protocol that provides multiprotocol encapsulation. PPP is used for Link Layer and Network Layer configuration. Provides a standard method for transporting multiprotocol datagrams over point-to-point links. Defined in RFC 1661, The Point-to-Point Protocol (PPP).

remote monitoring. Standard MIB that defines current and historical MAC-layer statistics and control objects, allowing you to capture real-time information across the entire network. This allows you to detect, isolate, diagnose, and report potential and actual network problems.

Internet Control Message Protocol (ICMP) echo request used in router discovery to enable a host to discover addresses of operating routers on the subnet.

Neighbor Discovery Protocol. Used by IPv6 nodes on the same link to discover each other’s presence, determine each other’s Link Layer addresses, find routers, and maintain reachability information about the paths to active neighbors. NDP is defined in RFC 2461 and is equivalent to the Address Resolution Protocol (ARP) used with IPv4. See also ARP.

Synchronous Optical Network. High-speed (up to 2.5 Gbps) synchronous network specification developed by Bellcore and designed to run on optical fiber. STS1 is the basic building block of SONET. Approved as an international standard in 1988. See also SDH.

Automatic Protection Switching. Technology used by SONET ADMs to protect against circuit faults between the ADM and a router and to protect against failing routers. See also ADM.

Virtual Router Redundancy Protocol. On Fast Ethernet and Gigabit Ethernet interfaces, enables you to configure virtual default routers.