Transition Networks, Inc.
S4224 Web User Guide
33595 Rev. C
Page 636 of 669
CC Monitoring (Continuity Checks Monitoring)
Fault detection uses the Continuity Check protocol to detect both connectivity failures and unintended
connectivity between service instances. Each MEP can periodically transmit a multicast Connectivity Check
Message (CCM) announcing the identity of the MEP and its MA, and tracks the CCMs received from the other
MEPs. All connectivity faults that can misdirect a CCM show up as differences between the CCMs received and
the MEP’s configured expectations. The state of the tracked CCMs can be displayed.
Each Continuity Check Message (CCM) is a multicast CFM PDU transmitted periodically by a MEP to ensure
continuity over the MA to which the transmitting MEP belongs. No reply is sent by any MP in response to
receiving a CCM. CCMs use addresses from the Continuity Check Message Group Destination MAC Address
table. The CCM can be sent away from or towards the MAC Relay Entity.
CCM
CCM is an acronym for
C
ontinuity
C
heck
M
essage. It is a OAM frame transmitted from a MEP to its peer MEP
and used to implement CC functionality.
CDP
CDP (Cisco Discovery Protocol) is a Cisco proprietary Layer 2 protocol that is media- and protocol-independent,
and runs on Cisco routers, bridges, access servers, and switches. A Cisco device with CDP enabled sends out
periodic interface updates to a multicast address in order to make itself known to neighbors. As a layer two
protocol, these packets (frames) are not routed. Using SNMP with the CDP MIB lets network management
applications learn the device type and the SNMP agent address of neighboring devices, and to then send
SNMP queries to those devices.
CIST
Acronym for
C
ommon and
I
nternal
S
panning
T
ree. Concerning IST/CST/CIST, IST is the only instance that can
send and receive BPDUs in the MST network. An MSTn instance is local to a region. ISTs in different regions
are interconnected via a Common Spanning Tree (CST). The CIST includes the collection of ISTs in each MST
region, and the CST that connects the ISTs.
The CIST is the default spanning tree instance of MSTP (i.e., all VLANs that are not members of particular
MSTIs are members of the CIST. Also, an individual MST region can be regarded a single virtual bridge by
other MST regions. The spanning tree that runs between MSTP regions is the CIST.
Clock
In PTP, a node participating in the Precision Time Protocol (PTP) that is capable of providing a measurement of
the passage of time since a defined epoch.
Commonly Used EtherTypes
The ‘EtherType’ field in an Ethernet frame indicates the protocol used in the data field of the frame. According to
the IEEE 802.3, Length/EtherType field is a two-octet field which takes one of two meanings, depending on its
numeric value. For numeric evaluation, the first octet is the most significant octet; when the value of this field is
≥ 1536 decimal (0600 hex) the EtherType field indicates the nature of the MAC client protocol (EtherType
interpretation). The value of the Type Field is obtained from the IEEE EtherType Field Registrar. The EtherType
field is a very limited space and assignments are limited. The EtherType field is administered by the IEEE RAC
EtherType Field Approval Authority.
