C
captive portal
A browser-based
authentication mechanism that forces unauthenticated users to a web page.
carrier VLAN
In
STP, carrier VLANs define the scope of the
STPD, including the physical and logical ports that belong to the STPD as well as the 802.1Q
tags used to transport EMISTP- or PVST+-encapsulated BPDUs. Only one carrier VLAN can exist in
any given STPD.
CCM
In
CFM, connectivity check messages are CFM frames transmitted
periodically by a MEP to ensure connectivity across the maintenance entities to which the
transmitting MEP belongs. The CCM messages contain a unique ID for the specified domain.
Because a failure to receive a CCM indicates a connectivity fault in the network, CCMs
proactively check for network connectivity.
CDR
Call Data (Detail)
Record
. In Internet telephony, a call detail record is a data record that contains
information related to a telephone call, such as the origination and destination addresses of
the call, the time the call started and ended, the duration of the call, the time of day the
call was made and any toll charges that were added through the network or charges for operator
services, among other details of the call.
In essence, call accounting
is a database application that processes call data from your switch (PBX, iPBX, or key
system) via a CDR (call detail record) or SMDR (station message detail record) port. The
call data record details your system's incoming and outgoing calls by thresholds, including
time of call, duration of call, dialing extension, and number dialed. Call data is stored in
a PC database.
CEP
Customer Edge Port.
Also known as Selective Q-in-Q or C-tagged Service Interface. CEP is a role that is configured
in software as a CEP VMAN port, and connects a VMAN to specific CVLANs based on the CVLAN
CVID. The CNP role, which is configured as an untagged VMAN port, connects a VMAN to all other
port traffic that is not already mapped to the port CEP role.
CA certificate
A certificate
identifying a certificate authority. A CA certificate can be used to verify that a certificate
issued by the certificate authority is legitimate.
certificate
A document that
identifies a server or a client (user), containing a public key and signed by a certificate
authority.
Certificate Authority
(CA)
A trusted third-party
that generates and signs certificates. A CA may be a commercial concern, such as GoDaddy or
GeoTrust. A CA may also be an in-house server for certificates used within an
enterprise.
certificate
chain
An ordered set of
certificates which can be used to verify the identity of a server or client. It begins with a
client or server certificate, and ends with a certificate that is trusted.
certificate
issuer
The certificate
authority that generated the certificate.
Certificate Signing Request
(CSR)
A document containing
identifiers, options, and a public key, that is sent to a certificate authority in order to
generate a certificate.
certificate
subject
The server or client
identified by the certificate.
client
certificate
A certificate
identifying a client (user). A client certificate can be used in conjunction with, or in lieu
of, a username and password to authenticate a client.
CFM
Connectivity Fault
Management allows an ISP to proactively detect faults in the network for each customer service
instance individually and separately. CFM comprises capabilities for detecting, verifying, and
isolating connectivity failures in virtual bridged LANs.
Chalet
A web-based user
interface for setting up and viewing information about a switch, removing the need to enter
common commands individually in the CLI.
CHAP
Challenge-Handshake
Authentication Protocol. One of the two main authentication protocols used to verify a user's
name and password for PPP Internet connections. CHAP is more secure than because it performs a
three-way handshake during the initial link establishment between the home and remote
machines. It can also repeat the authentication anytime after the link has been
established.
checkpointing
Checkpointing is the
process of copying the active state configurations from the primary
MSM to the backup MSM on modular switches.
CIDR
Classless Inter-Domain
Routing. CIDR is a way to allocate and specify the Internet addresses used in interdomain
routing more flexibly than with the original system of IP address classes. This address
aggregation scheme uses supernet addresses to represent multiple IP destinations. Rather than
advertise a separate route for each destination, a router uses a supernet address to advertise
a single route representing all destinations.
RIP does not support CIDR;
BGP
and
OSPF support CIDR.
CIST
Common and Internal
Spanning Tree. In an
MSTP environment,
the CIST is a single spanning tree domain that connects MSTP regions. The CIST is responsible
for creating a loop-free topology by exchanging and propagating BPDUs across MSTP regions. You
can configure only one CIST on each switch.
CIST regional root
bridge
Within an
MSTP region, the bridge with the lowest path
cost to the CIST root bridge is the CIST regional root bridge If the CIST root bridge is
inside an MSTP region, that same bridge is the CIST regional root for that region because it
has the lowest path cost to the CIST root. If the CIST root bridge is outside an MSTP region,
all regions connect to the CIST root through their respective CIST regional roots.
CIST root
bridge
In an
MSTP environment, the bridge with the lowest
bridge ID becomes the CIST root bridge. The bridge ID includes the bridge priority and the MAC
address. The CIST root bridge can be either inside or outside an MSTP region. The CIST root
bridge is unique for all regions and non-MSTP bridges, regardless of its location.
CIST root port
In an
MSTP environment, the port on the CIST
regional root bridge that connects to the CIST root bridge is the CIST root port. The CIST
root port is the master port for all MSTIs in that MSTP region, and it is the only port that
connects the entire region to the CIST root bridge.
CLEAR-flow
CLEAR-Flow allows you
to specify certain types of traffic to perform configured actions on. You can configure the
switch to take an immediate, preconfigured action to the specified traffic or to send a copy
of the traffic to a management station for analysis. CLEAR-Flow is an extension to
ACLs, so you must be familiar with ACL policy
files to apply CLEAR-Flow.
CLI
Command Line Interface.
You can use the CLI to monitor and manage the switch or wireless appliance.
cluster
In
BGP, a cluster is formed within an
AS by a route reflector and its client
routers.
collision
Two Ethernet packets
attempting to use the medium simultaneously. Ethernet is a shared media, so there are rules
for sending packets of data to avoid conflicts and protect data integrity. When two nodes at
different locations attempt to send data at the same time, a collision will result. Segmenting
the network with bridges or switches is one way of reducing collisions in an overcrowded
network.
CNA
Converged Network
Analyzer. This application suite, available from Avaya, allows the server to determine the
best possible network path. The CNA Agent is a software piece of the entire CNA application
that you install on Extreme Networks devices. You use the CNA Agent software only if you are
using the Avaya CNA solution, and the CNA Agent cannot function unless you also obtain the
rest of the CNA application from Avaya.
CNP
Customer Network
Port.
combo port
Also known as a combination port. On some Extreme Networks devices (such as the
X440-G2 series switch), certain ports can be used as either copper or fibre ports.
combo link
In
EAPS, the common link is the physical link between the controller
and partner nodes in a network where multiple EAPS share a common link between
domains.
control VLAN
In
EAPS, the control VLAN is a VLAN that sends
and receives EAPS messages. You must configure one control VLAN for each EAPS
domain.
controller node
In
EAPS, the controller node is that end of the
common line that is responsible for blocking ports if the common link fails, thereby
preventing a superloop.
CoS
Class of Service.
Specifying the service level for the classified traffic type.
For more information, see QoS in the ExtremeXOS 21.1 User Guide.
CRC
Cyclic Redundancy
Check. This simple checksum is designed to detect transmission errors. A decoder calculates
the CRC for the received data and compares it to the CRC that the encoder calculated, which is
appended to the data. A mismatch indicates that the data was corrupted in transit.
CRC error
Cyclic redundancy check
error. This is an error condition in which the data failed a checksum test used to trap
transmission errors. These errors can indicate problems anywhere in the transmission
path.
CSPF
Constrained shortest
path first. An algorithm based on the shortest path first algorithm used in
OSPF, but with the addition of multiple
constraints arising from the network, the LSP, and the links. CSPF is used to minimize network
congestion by intelligently balancing traffic.
CVID
CVLAN ID. The CVID
represents the CVLAN tag for tagged VLAN traffic. (See
CVLAN.)