See Authentication, Authorization, and Accounting.
Access Control List
A list kept by routers to control access to or from the router for a number of services (for example, to prevent packets with a certain IP address from leaving a particular interface on the router).
ACK
Acknowledged. Notification sent from one network device to another to acknowledge that some event occurred (for example, the receipt of a message).
ACL
See Access Control List.
Active
Denotes a card or process that performs a system task; in a redundant configuration, there is an inactive standby card or process available to become active. Active cards or processes are also sometimes denoted as primary.
Active Software Set
The set of Cisco IOS-XR software packages activated in one or more nodes in a Cisco CRS-1 Series router.
Active RP
The RP that is active in a redundant pair of RPs. The primary RP in slot 0 is set as the active RP as system boot up.
Active Software Configuration
The software configuration marked as active for a node.
APS
Automatic protection switching. A method that allows transmission equipment to recover automatically from failures, such as a cut cable.
Authentication, Authorization, and Accounting
A network security service that provides the primary framework to set up access control on a Cisco CRS-1 router or access server. AAA is an architectural framework and modular means of configuring three independent, but closely related security functions in a consistent manner.
B
Bandwidth
The amount of data that can be transmitted in a fixed amount of time. For digital devices, the bandwidth is usually expressed in bits per second (Bps) or bytes per second.
Benes
Switching algorithm used in fabric between stages. In this Benes network, the path that the data takes through the network is calculated in a concentrated control circuit from the interconnection between input ports and output ports.
BER
See bit error rate.
BGP
See Border Gateway Protocol.
bistate alarm
An alarm that once activated stays active until it is cleared by the process that activated it.
bit error rate
Ratio of received bits that contain errors.
Border Gateway Protocol
A routing protocol used between autonomous systems. It is the routing protocol that makes the internet work. BGP is a distance-vector routing protocol that carries connectivity information and an additional set of BGP attributes. These attributes allow for a rich set of policies for deciding what the best route to reach a given destination is.
C
card type
The type of the card inserted in a slot.
CDP
See Cisco Discovery Protocol.
Cisco.com
The Cisco Web site.
Cisco Discovery Protocol
Runs on all Cisco devices so that these devices can learn about neighboring devices and exchange information. CDP uses a well-known multicast Media Access Control (MAC) address. During system initialization, the application-specific integrated circuit (ASIC) is configured to forward these packets to the Cisco IOS Software CPU, which processes the packets.
class map
Used for matching packets to a specific class.
class of service
See CoS.
CLI
command-line interface. A text-based user interface to an operating system. A command line interface is a user interface to a computer's operating system or an application in which the user responds to a visual prompt by typing in a command on a specified line, receives a response back from the system, and then enters another command, and so forth. Typically, most of today's UNIX-based systems offer both a command line interface and a graphical user interface.
Committed/Saved Software Configuration
The configuration stored in the system for a particular node. The RP loads the committed configuration into memory at startup.
Composite Directory
The directory for a composite PIE file used to manage all the corresponding packages as a group.
Configuration register
In Cisco routers, a 16-bit, user-configurable value that determines how the router functions during initialization. The configuration register can be stored in hardware or software. In hardware, the bit position is set using a jumper. In software, the bit position is set by specifying a hexadecimal value using configuration commands. Hexadecimal or decimal value that represents the 16-bit configuration register value that you want to use the next time the router is restarted. The value range is from 0x0 to 0xFFFF (0 to 65535 in decimal).
Control Plane
The control plane oversees the operation of the data plane, allocating resources, providing information, and handling errors to allow Data Plane operations to be continuous and efficient.
CORBA
Common Object Request Broker Architecture. Specification that provides the standard interface definition between OMG-compliant objects. CORBA allows applications to communicate with one another no matter where they are located or who has designed them.
CoS
class of service. An indication of how an upper-layer protocol requires a lower-layer protocol to treat its messages. In SNA subarea routing, CoS definitions are used by subarea nodes to determine the optimal route to establish a given session. A CoS definition comprises a virtual route number and a transmission priority field. Repetitive, regularly timed signals are used to control synchronous processes.
Craft Works Interface
See CWI.
CWI
Craft Works Interface. Graphic User Interface (GUI) used to configure and operates a Cisco CRS-1 Series routing system. The CWI client runs in a web browser.
D
Distributed Route Processor
Available after the initial release of the system. Optional additional processor boards that run control software on the Cisco CRS-1 Series routing system. DRPs are installed in line card slots and require an additional DRP PLIM. See also Route Processor (RP).
DNS
Domain Naming System. Mechanism used in the internet and on private intranets for translating names of host computers into addresses. The DNS also allows host computers not directly on the Internet to have a registered names in the same style.
DPT
Dynamic Packet Transport.
DRP PLIM
The DRP PLIM is an optional card that is used when an optional DRP is used. The DRP PLIM goes into the Line Card chassis from the PLIM-side in the slot corresponding to the DRP.
DRP
See Distributed Route Processor.
dSC
Designated shelf controller. The physical shelf controller that serves the entire Cisco CRS-1 Series routing system as the designated "master" SC. The dSC is selected from among the Route Processors (RPs) installed in the line card chassis.
Dynamic Packet Transport
Dynamic Packet Transport (DPT) rings are dual, counter-rotating fiber rings. Both fibers are used concurrently to transport both data and control traffic.
E
Egress
Outgoing channel.
Ethernet
A type of networking technology for local area networks. See also Fast Ethernet.
extensible markup language
See XML.
Exterior Gateway Protocol
See EGP.
external Border Gateway Protocol
See eBGP.
F
Fabric
Connectivity between all line cards. Also referred to as switch fabric.
Failover
See Switchover.
fan controller
Two fan controller cards are installed in every line card chassis as a redundant pair to manage the fan assemblies; there is a BITS timing connector on the fan controller card.
Fan Trays
Two fan trays will go in every Line Card Chassis or every Switch Fabric Chassis. Different fan trays used in both chassis.
Fast Ethernet
A version of Ethernet which can carry 100 Mbps compared with standard Ethernet's 10 Mbps.
fast reroute
Automatically reroutes traffic on a label switch path (LSP) if a node or link in an LSP fails. FRR reduces the loss of packets traveling over an LSP.
FC
See fan controller
FE
See Fast Ethernet.
FIB
See Forwarding Information Base.
Fiber Module
Installed in the fabric chassis.
FM
See Fiber Module.
flooding
Traffic passing technique used by switches and bridges in which traffic received on an interface is sent out all the interfaces of that device except the interface on which the information was received originally.
Forwarding
Process of sending a frame toward its ultimate destination by way of an internetworking device.
Forwarding Information Base
Database that stores information about switching of data packets. A FIB is based on information in the RIB. It is the optimal set of selected routes that are installed in the line cards for forwarding.
Frame Relay
Industry-standard, switched data link layer protocol that handles multiple virtual circuits using High-Level Data Link Control (HDLC) encapsulation between connected devices. Frame Relay is more efficient than X.25, the protocol for which it generally is considered a replacement.
FRR
See fast reroute.
FTP
File Transfer Protocol Application protocol, part of the TCP/IP protocol stack, used for transferring files between network nodes. FTP is defined in RFC 959.
G
Gbps
Gigabits per second. The amount of data that can be transmitted in a fixed amount of time. 1 gigabit = 230 bits, 1,073,741,824 bits.
GE
Gigabit Ethernet.
Gigabit Ethernet
The Ethernet speed for the Cisco CRS-1 Series router control bus running between all chassis.
graceful restart
Restart that does not impact any router processes.
graphical user interface
Graphics-based user interface that incorporates windows, menus, buttons, and a mouse.
GRE
Generic Route Encapsulation (an IP tunnel within IP). Tunneling protocol developed by Cisco and adapted by the IETF as a standard protocol defined in several RFCs. GRE can encapsulate a wide variety of protocol packet types inside IP tunnels, creating a virtual point-to-point link to Cisco routers at remote points over an IP internetwork. By connecting multiprotocol subnetworks in a single-protocol backbone environment, IP tunneling using GRE allows network expansion across a single-protocol backbone environment.
GUI
See graphical user interface.
H
HA
See High Availability.
HDLC
See High-Level Data Link Controller.
High Availability
High availability is defined as the continuous operation of systems. For a system to be available all components including application and database servers, storage devices and the end-to-end network need to provide continuous service.
High-Level Data Link Controller
High-Level Data Link Controller. ISO communications protocol used in X.25 packet switching networks. HDLC provides error correction at the data link layer and contains the following subsets: LAP, LAPB, and SDLC.
Hop
Passage of a data packet between two network nodes (for example, between two routers). See also hop count.
Hop Count
Routing metric used to measure the distance between a source and a destination.
HTTP
Hypertext Transfer Protocol. Used by web browsers and web servers to transfer files, such as text and graphic files. The Hypertext Transfer Protocol (HTTP) is the set of rules for exchanging files (text, graphic images, sound, video, and other multimedia files) on the World Wide Web. Relative to the TCP/IP suite of protocols (which are the basis for information exchange on the Internet), HTTP is an application protocol.
Hypertext Transfer Protocol
See HTTP.
I
iBGP
internal Border Gateway Protocol. BGP sessions are established between routers in the same autonomous system.
ICMP
Internet Control Message Protocol. Network layer Internet (TCP/IP) protocol that reports errors and provides other information relevant to IP packet processing.
IEP
IP explicit path. List of IP addresses, each representing a node or link in the explicit path.
IETF
Internet Engineering Task Force.
IGMP
Internet Group Management Protocol. Governs the management of multicast groups in a TCP/IP network. Used by IP hosts to report their multicast group memberships to an adjacent multicast router.
IGP
See Interior Gateway Protocol.
Ingress
Incoming channel.
Installed Software Set
The set of Cisco IOS-XR software packages installed on a Cisco CRS-1 Series router.
IOS-XR
The Cisco operating system used on Cisco CRS-1 Series routers and Cisco 12000 Series routers.
Incremental Shortest Path First
See ISPF.
Interior Gateway Protocol
IGP. Internet protocol used to exchange routing information within an autonomous system. Examples of common Internet IGPs include IGRP, OSPF, and RIP.
Intermediate System-to-Intermediate System
IS-IS. Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol based on DECnet Phase V routing, whereby ISs (routers) exchange routing information based on a single metric to determine network topology.
Internet Control Message Protocol
ICMP. Internet Control Message Protocol. Network layer Internet protocol that reports errors and provides other information relevant to IP packet processing. Documented in RFC 792.
Internet Engineering Task Force
IETF. Internet Engineering Task Force. Task force consisting of over 80 working groups responsible for developing Internet standards. The IETF operates under the auspices of ISOC.
Internet Group Management Protocol
IGMP. Internet Group Management Protocol. Used by IP hosts to report their multicast group memberships to an adjacent multicast router.
Internetwork Packet Exchange
IPX. Internetwork Packet Exchange. NetWare network layer (Layer 3) protocol used for transferring data from servers to workstations. IPX is similar to IP and XNS.
IP
Internet Protocol. Network layer protocol in the TCP/IP stack offering a connectionless internetwork service. IP provides features for addressing, type-of-service specification, fragmentation and reassembly, and security.
IPv4
IP Version 4. Network layer for the TCP/IP protocol suite. A connectionless, best-effort packet switching protocol.
IPv6
IP Version 6. Replacement for IPv4. A next generation IP protocol. IPv6 is backward compatible with and is designed to fix the shortcomings of IPv4, such as data security and maximum number of user addresses. IPv6 increases the address space from 32 to 128 bits, providing for an unlimited number of networks and systems. It also supports quality of service (QoS) parameters for real-time audio and video.
IPX
Internetwork Packet Exchange. NetWare network layer (Layer 3) protocol used for transferring data from servers to workstations. IPX is similar to IP and XNS.
IS-IS
Intermediate System-to-Intermediate System. OSI link-state hierarchical routing protocol based on DECnet Phase V routing, whereby ISs (routers) exchange routing information based on a single metric to determine network topology.
ISPF
Incremental Shortest Path First (SPF).
J
K
keepalive interval
Period of time between each keepalive message sent by a network device.
keepalive message
Message sent by one network device to inform another network device that the virtual circuit between the two is still active.
L
Label Distribution Protocol
A standard protocol between MPLS-enabled routers to negotiate the labels (addresses) used to forward packets. The Cisco proprietary version of this protocol is the Tag Distribution Protocol (TDP).
Layer 2
Layer 2 refers to the Data Link layer of the commonly-referenced multi-layered communication model, Open Systems Interconnection (OSI) The Data Link layer contains the address inspected by a bridge or switch. Layer 2 processing is faster than layer 3 processing, because less analysis of the packet is required.
Layer 3
Layer 3 refers to the Network layer of the commonly-referenced multi-layered communication model, Open Systems Interconnection (OSI). The Network layer is concerned with knowing the address of the neighboring nodes in the network, selecting routes and quality of service, and recognizing and forwarding to the Transport layer incoming messages for local host domains.
A router is a layer 3 device, although some newer switches also perform Layer 3 functions. The Internet Protocol (IP) address is a Layer 3 address.
LC
See line card
LDP
See Label Distribution Protocol.
line card
Line cards in the Cisco CRS-1 Series system are referred to as modular services cards (MSCs). See modular services card.
lineup
A list of component versions. A lineup may be associated with a package, a SMU, or a project.
Logical Router
A Cisco CRS-1 Series routing system can be partitioned into several logical routers, each of which is managed independently.
loopback
Send the outgoing signals back to the receiving side for testing purposes.
LR
See Logical Router.
LSP
label switch path and link-state packet.
LSR
label switch router. The role of an LSR is to forward packets in an MPLS network by looking only at the fixed-length label.
M
MAC Address
Media Access Control. The hardware address of a device.
maximum transmission unit
See MTU.
MIB
Management Information Base. Database of network management information that is used and maintained by a network management protocol like SNMP
Modular Services Card
Module where the ingress and egress packet processing and queuing functions are carried out in the Cisco CRS-1 Series router architecture. Up to 16 MSCs are installed in a line card chassis; each MSC must have an associated PLIM (of which there are several types to provide a variety of physical interfaces). The MSC and PLIM mate together on the line card chassis midplane.
MSCs are also referred to as line cards.
MOSPF
See multicast OSPF.
MPLS
See Multiprotocol Label Switching traffic engineering.
Maximum Transmission Unit. The size of the largest packet which can be processed by an interface.
multicast OSPF
Intradomain multicast routing protocol used in OSPF networks. Extensions are applied to the base OSPF unicast protocol to support IP multicast routing.
Multiprotocol Label Switching traffic engineering
Multiprotocol Label Switching. A switching method that forwards IP traffic using a label. This label instructs the routers and the switches in the network where to forward the packets based on preestablished IP routing information.
MSC
See Modular Services Card.
N
Node
A card installed and running on a Cisco CRS-1 Series routing system.
Non-stop forwarding
See NSF.
NSF
Non-stop forwarding. Packets keep flowing during events such as failover, process restarts, and the upgrade/downgrade of software packages.
NVRAM
Non-Volatile Random Access Memory. Static random access memory which is made into non-volatile storage by having a battery permanently connected.
O
OIR
On-line Insertion and Removal: the ability to insert or remove cards from a running chassis or system without adversely affecting either the system or the card itself.
Open Shortest Path First
Open Shortest Path First. Link-state, hierarchical Interior Gateway Protocol (IGP) routing algorithm proposed as a successor to RIP in the Internet community. OSPF features include least-cost routing, multipath routing, and load balancing. OSPF was derived from an early version of the IS-IS protocol.
OSI
OSI Internet Management. Group tasked with specifying ways in which OSI network management protocols can be used to manage TCP/IP networks.
OSPF
See Open Shortest Path First.
P
package
A group of software components installed ona Cisco CRS-1 Series routing system.
Package Installation Envelopes
See PIE file.
packet
Logical grouping of information that includes a header containing control information and (usually) user data. Packets most often are used to refer to network layer units of data.
packet-over-SONET
POS. Packet-over-SONET enables core routers to send native IP packets directly over SONET or SDH frames.
PAP
Password Authentication Protocol. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and the host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access but merely identifies the remote end. The router or access server then determines whether that user is allowed access. PAP is supported only on PPP lines.
PAROLI
Parallel Optical Link: used to interconnect line card and fabric chassis within Cisco CRS-1 Series routing system.
Password Authentication Protocol
PAP. Authentication protocol that allows PPP peers to authenticate one another. The remote router attempting to connect to the local router is required to send an authentication request. Unlike CHAP, PAP passes the password and the host name or username in the clear (unencrypted). PAP does not itself prevent unauthorized access but merely identifies the remote end. The router or access server then determines whether that user is allowed access. PAP is supported only on PPP lines.
PCMCIA
Personal Computer Memory Card International Association. Standard for credit card-size memory or I/O device.
PIE file
Package Installation Envelope. An installable software file with suffix.pie. A pie may be a package or an SMU. A PIE is used to deliver IOS-XR software. A PIE may contain a single component, a group of components (called a package), or a set of packages. When a PIE contains more than one package it is called a "Composite PIE."
PLIM
Physical Line Interface Module. Provides the physical interface for a line card. Also handles media-specific functions, such as framing, clock recovery, channelization, and optical signaling for line interfaces connecting to a Cisco CRS-1 Series routing system.
Point Of Presence
A physical location where an Internet Service Provider installs equipment to interconnect with a local exchange carrier.
Point-to-Point Protocol
PPP. Successor to SLIP that provides router-to-router and host-to-network connections over synchronous and asynchronous circuits. Whereas SLIP was designed to work with IP, PPP was designed to work with several network layer protocols, such as IP, IPX, and ARA. PPP also has built-in security mechanisms, such as CHAP and PAP. PPP relies on two protocols: LCP and NCP.
POP
See Point Of Presence. A (typically large) service provider location that houses telecommunication and networking equipment.
policy map
Specifies the traffic policy name and configures a traffic policy.
POS
See packet-over-SONET.
power shelves
Two power shelves are installed in each chassis. The type of power shelf varies by installation. The available types are: Delta AC Power Shelf, Wye AC Power Shelf and DC Power Shelf.
PPP
See Point-to-Point Protocol.
primary
Denotes a card or process that performs a system task; in a redundant configuration, there is an inactive standby card or process available to become the primary. Active cards or processes are also sometimes denoted as active.
primary RP
The active route processor installed on a chassis. Each chassis contains two RPs, one to act as the primary, or active, RP, and the other as the standby, or redundant, RP.
Q
QOS
Quality of Service. A set of parameters which describe a flow of data, such as: guaranteed bandwidth, delay, and delivery guarantee
R
Rack OIR
An event denoting the insertion or removal of an entire line card or fabric chassis into a system. In the dSC context, it indicates the insertion/removal of a SC into the control plane through the Control Plane Ethernet. It does not have any relationship with fabric OIR.
RCP
Remote Copy Protocol. A protocol that allows users to copy files to and from a file system residing on a remote host or server on the network. The RCP protocol uses TCP to ensure the reliable delivery of data.
Resource Reservation Protocol
See RSVP.
RIB
Routing Information Base. This is the set of all available routes to choose the FIB from. The RIB essentially contains all routes available for selection. Essentially it is the sum of all routes learned via dynamic routing protocols, all directly attached networks (i.e. networks which a given router has interfaces connected to), and any additional configured routes such as static Routes.
RIP
Routing Information Protocol. An Interior Gateway Protocol (IGP) supplied with UNIX BSD systems. The most common IGP in the Internet. RIP uses hop count as a routing metric. See also hop count, IGP, and OSPF.
ROM Monitor
ROMMON. The ROM Monitor program is executed from FLASH or ROM and is a single threaded program that initializes a board and loads a higher level operating system. ROMMON can be used for debugging or to manually boot the system.
Route Processor
RP. Cards that contain run control software on the Cisco CRS-1 Series routing system. Two RPs are installed as a redundant pair in dedicated slots in the front of each line card chassis. See also Distributed Route Processor (DRP).
router
Network layer device that uses one or more routing metrics to determine the optimal path along which network traffic should be forwarded. Routers forward packets from one network to another based on network layer information.
routing
Process of finding a path to a destination host. Routing is very complex in large networks because of the many potential intermediate destinations a packet might traverse before reaching its destination host.
routing domain
Group of end systems and intermediate systems operating under the same set of administrative rules. Within each routing domain is one or more areas, each uniquely identified by an area address.
routing metric
A routing algorithm determines that one route is better than another. This information is stored in routing tables. Metrics include bandwidth, communication cost, delay, hop count, load, MTU, path cost, and reliability. Sometimes referred to simply as a metric.
An algorithm is a well-defined rule or process for arriving at a solution to a problem. In networking, algorithms commonly are used to determine the best route for traffic from a particular source to a particular destination.
routing protocol
Protocol that accomplishes routing through the implementation of a specific routing algorithm. Examples of routing protocols include BGP, OSPF, and IS-IS.
routing table
Table stored in a router or some other internetworking device that keeps track of routes to particular network destinations and, in some cases, metrics associated with those routes.
RP
See Route Processor.
RPC
Remote Procedure Call. Technological foundation of client/server computing. RPCs are procedure calls that are built or specified by clients and executed on servers, with the results returned over the network to the clients.
RPF
Reverse Path Forwarding. Part of the multicast forwarding algorithm for determining if a packet should be forwarded or not.
RSVP
Resource Reservation Protocol. Protocol that supports the reservation of resources across an IP network. Applications running on IP end systems can use RSVP to indicate to other nodes the nature (bandwidth, jitter, maximum burst, and so on) of the packet streams they want to receive. RSVP depends on IPv6. Also known as Resource Reservation Setup Protocol. See also IPv6.
Running Configuration
The router configuration currently in effect. Although, the user can save multiple versions of the router configuration for future reference, there is only one copy of the running configuration in the router at any given time.
Rx
The receiver end of a fabric link. All links are unidirectional. See also Tx.
S
S/2 Switch Module
The switch module containing only S2 switch fabric elements. Located in the fabric chassis.
S1 Stage
Fabric stage. Distribute traffic across all S2 stages.
S1, S2, S3
Stages of the switch fabric. Data enters the switch fabric from one of the `sprayer' ASICs on a line card, then passes through an S1 element, an S2 element, an S3 element and finally arrives at one of the `sponge' ASICs on the destination line cards.
S1/3 Switch Module
The switch module containing stages S1 and S3 of the switch fabric. Eight S1/3 boards are located in each line card rack of a multichassis Cisco CRS-1 Series routing system.
S123 Switch Module
A fabric card that contains all three stages of the switch fabric. Eight S123 boards are located in the line card racks for a 16-slot single-chassis configuration.
S123T Switch Module
A type of fabric card that contains all three stages of the switch fabric and optical fiber connectors. Functionally the same as the S123 SM. Includes an additional optical interface to cross connect the line card chassis in a dual chassis configuration. Eight 1T boards are used in each chassis of the dual-chassis configuration.
S2 Stage
Fabric stage. Primarily switching. Queuing based on which S3 stage it's going to.
S3 Stage
Fabric stage. Switching. Queuing based on egress fabric channel.
SC
System Controller on the Cisco CRS-1 Series router.
SCFC
Shelf controller/fan controller. Combines Shelf Controller function and fan controller function on one card. Two are installed in each Fabric chassis.
SCRP
Shelf Controller/Route Processor. See Shelf Controller.
SCTP
Stream Control Transmission Protocol. An alternative protocol to TCP. SCTP contains multiple transmission paths and is designed to facilitate SS7 signaling over TCP/IP, supporting multiple IP addresses from the same host and treating the data streams from these addresses as one session. It does not require a strict order of delivery like TCP. If one data stream fails, the other streams are allowed to continue.
SDH
Synchronous Digital Hierarchy. European standard that defines a set of rate and format standards that are sent using optical signals over fiber. SDH is similar to SONET, with a basic SDH rate of 155.52 Mbps, designated at STM-1.
SDRAM
Synchronous Dynamic Random Access Memory. A form of Dynamic RAM which adds a separate clock signal to the control signals.
Service Processor
SP. service Processor. A SP on each card maintains an internal management connection to the Shelf Controller for the rack. The SP is referred to in CLI commands to identify the nodeID for fabric, alarm and fan controller cards. Example: RP/0/RPO/CPU:router# admin show controllers fabric connectivity location 0/SM0/SP
Shelf Controller
See System Controller.
Shelf Manager
The shelf manager process runs on a router or switch, doing platform-dependent functions, including handling OIR events. Shelf Manager is formerly called platform manager.
SM
Switch Module.
SMU
Software Maintenance Upgrade. A "point fix" for a critical problem. SMUs are delivered as PIE files and are used to update software packages.
SNMP
Simple Network Management Protocol. SNMP is the protocol governing network management and the monitoring of network devices and their functions. It is not necessarily limited to TCP/IP networks.
Snoop
A function of the fabric that copies all traffic entering the fabric from an interface to another interface.
Software Configuration
A list of packages activated for a particular node. A software configuration consists of a boot package and additional feature packages.
SONET
Synchronous Optical Network. A broadband networking standard based on point-to-point optical fibre networks.
SP
See Service Processor.
SPE
Synchronous Payload Envelope. Portion of the SONET frame containing overhead information (POH and user data).
SPF
shortest path first. Routing algorithm that iterates on length of path to determine a shortest-path spanning tree. Commonly used in link-state routing algorithms. Sometimes called Dijkstra's algorithm.
Sponge
The reassembly and resequencing ASIC that takes cells from the switch fabric and converts them into packets. The packets are then queued up at the egress (outgoing) path.
Sprayer
The segmentation ASIC located in the ingress (incoming) path of line cards that takes packets, segments them into cells and transmits them to the fabric.
SRP
Spatial Reuse Protocol (another name for DPT which is a ring based IP protocol).
sRP
Standby RP.
SSH
Secure Shell. A protocol that provides a secure remote connection to a router through a Transmission Control Protocol (TCP) application.
SSL
Secure Socket Layer.
standby
Denotes an inactive card or process that waits to become active; standby cards or processes are also sometimes denoted as backup.
startup configuration
The router configuration designated to be applied on next router startup.
switch module
Provides switch fabric functionality. The S2 SM is installed in the fabric chassis. The line card chassis contains either the S1/S2/S3. the S1/S3 or the S1/S2/S3T, depending on the configuration of the system.
switchover
A switch between the active and standby cards; the old active card may be dead prior to switchover (death of the active card is one of the causes for the switchover). Also known as failover.
system controller
The hardware component that manages configuration and health of a chassis within the Cisco CRS-1 Series routing system. In the line card chassis, the SC is part of the RP module. In the fabric chassis, the SC is a separate Shelf Controller module. In this document, SC could refer to either RP (Line Card chassis) or SC (Fabric chassis), unless explicitly mentioned as one or the other.
system reload
Reload of an Cisco CRS-1 Series router node.
system restart
Soft reset of an Cisco CRS-1 Series router node. This involves restarting all the processes running on that node.
T
TAC
Technical Assistance Center.
TACACS
Terminal Access Controller Access Control System. Authentication protocol, developed by the DDN community, that provides remote access authentication and related services, such as event logging. User passwords are administered in a central database rather than in individual routers, providing an easily scalable network security solution.
target configuration
A "two-stage" configuration of the IOS-XR running configuration. This allows users to make changes to the running configuration and accept these changes by entering the "commit" command.
Tbps
Terabits per second = 1,000,000,000,000 (one trillion) bits per second. The amount of data that can be transmitted in a fixed amount of time.
TCP
Transmission Control Protocol. Connection-oriented transport layer protocol that provides reliable full-duplex data transmission. TCP is part of the TCP/IP protocol stack.
telnet
Standard terminal emulation protocol in the TCP/IP protocol stack. Telnet is used for remote terminal connection, enabling users to log in to remote systems and use resources as if they were connected to a local system. Telnet is defined in RFC 854.
terabyte
A unit of computer memory or data storage capacity equal to 1,024 gigabytes (240 bytes). Approximately one trillion bytes.
TFTP
Trivial File Transfer Protocol. A simplified version of FTP that allows files to be transferred from one computer to another over a network, usually without the use of client authentication (for example, username and password).
Note: some TFTP servers (such as Sun Solaris) may not support file sizes larger that 32 MB.
tunnel
Communication path between two peers, such as two routers.
Tx
The transmitter end of a fabric link. All links are unidirectional. See also Rx.
U
UDP
User Datagram Protocol. Connectionless transport layer protocol in the TCP/IP protocol stack. UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery, requiring that error processing and retransmission be handled by other protocols. UDP is defined in RFC 768.
unicast
When sending a message to one receiver in a communications network, and multiple users request the same data from the same server at the same time, duplicate data streams are sent, one to each user.
V
VPN
Virtual Private Network. Enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one network to another. A VPN uses "tunneling" to encrypt all information at the IP level.
W
WRED
Weighted Random Early Detection. Queueing method that ensures that high-precedence traffic has lower loss rates than other traffic during times of congestion.
X
XML
extensible markup language. A standard maintained by the World Wide Web Consortium (W3C) that defines a syntax that lets you create markup languages to specify information structures. Information structures define the type of information, for example, subscriber name or address, not how the information looks (bold, italic, and so on). External processes can manipulate these information structures and publish them in a variety of formats. XML allows you to define your own customized markup language.
