Transition Networks, Inc.
S4224 Web User Guide
33595 Rev. C
Page 650 of 669
An LTM is used to signal to the MEP to transmit an LTM and to create an LTM entry in the MEP’s Linktrace
Database. The MA End Point can then be examined to determine whether or not the corresponding LTRs have
been received by the MEP.
ETH-LT (Ethernet Link Trace) is an on-demand OAM function that can be used 1) to retrieve adjacency
relationship between a MEP and a remote MEP or MIP, and 2) for Fault localization – when a fault (e.g., a link
and/or a device failure) occurs, the sequence of MIPs and/or MEP will likely differ from the expected sequence.
These differences provide information about the fault location.
ETH-LT request information is initiated in a MEP on an on-demand basis. After transmitting a frame with ETH-
LT request information, the MEP expects to receive frames with ETH-LT reply information within a specified
period of time. Network elements containing MIPs or MEPs and receiving the frame with ETH-LT request
information respond selectively with frames containing ETH-LT reply information.
LLAG
(Local Link Aggregation Group) is one of two supported types of Link Aggregation Groups (same as Link
Aggregation Group). With LLAG, all ports in an LLAG must reside on the same unit, any number of LLAGs may
be configured for each unit in a stack, and each LLAG may consist of up to 16 ports. LLAGs are configured the
same way as link aggregation groups for a standalone device (e.g., S4224).
For both LLAGs and GLAGs, the egress port is chosen based on an ‘aggregation code’ that is calculated for the
frame. This ensures that frames relating to a given frame flow are forwarded on the LLAG or GLAG member
port, and thus do not risk being re-ordered. See also “GLAG”.
LLC
The IEEE 802.2
L
ogical
L
ink
C
ontrol (LLC) protocol provides a link mechanism for upper layer protocols. It is
the upper sub-layer of the Data Link Layer and provides multiplexing mechanisms that make it possible for
several network protocols (IP, IPX) to coexist within a multipoint network. LLC header consists of 1 byte DSAP
(Destination Service Access Point), 1 byte SSAP (Source Service Access Point), 1 or 2 bytes Control field
followed by LLC information.
LLDP
LLDP is an IEEE 802.1ab standard protocol. The
L
ink
L
ayer
D
iscovery
P
rotocol (LLDP) specified in this
standard allows stations attached to an IEEE 802 LAN to advertise, to other stations attached to the same IEEE
802 LAN, the major capabilities provided by the system incorporating that station, the management address or
addresses of the entity or entities that provide management of those capabilities, and the identification of the
stations point of attachment to the IEEE 802 LAN required by those management entity or entities. The
information distributed via this protocol is stored by its recipients in a standard Management Information Base
(MIB), making it possible for the information to be accessed by a Network Management System (NMS) using a
management protocol such as the Simple Network Management Protocol (SNMP).
LLDP-MED
LLDP-MED Link Layer Discovery Protocol Media Endpoint Discovery. LLDP-MED is an extension of IEEE
802.1ab and is defined by the Telecommunication Industry Association (TIA-1057).
LLDPDU
Link Layer Discovery Protocol Data Unit, as defined in IEEE 802.1AB.
