Link Layer Discovery Protocol (LLDP) - Extreme Networks

Link Layer Discovery Protocol (LLDP)
A New Standard for Discovering and Managing Converged Network Devices
If there is any certainty in the access layer of a network, it is
that the number and the complexity of devices that reside
in this layer will continue to experience rapid growth.
Ethernet access ports are expected to more than triple from
2004 to 2007 (IDC Research, 2004). This exponential
growth in the number of devices requiring LAN connectivity
is due largely to the proliferation of new applications such
as IP Telephony and wireless access.
From a network management perspective, there are direct
implications that come from these changes. In the past,
many network equipment vendors have developed proprietary
discovery methods in order to incorporate new access
devices that they develop. In addition, key infrastructure
vendors have developed proprietary discovery protocols,
storing the data in an enterprise extension of the Management
Information Base (MIB) used with Simple Network
Management Protocol (SNMP). Today’s network management
solutions are required to add expanded functionality
and, at the same time, reduce complexity. Deployment,
configuration, monitoring and other management disciplines
must accommodate new technologies and network changes
that are necessary to support new applications. Further,
management systems must incorporate features that meet
or exceed existing TDM voice solutions while providing
advanced functionality to take advantage of the data
infrastructure.
Extreme Networks ® simplifies today’s expanding network
environment and management challenges by improving
intelligence and automation throughout the network.
Extreme Networks now incorporates the recently finalized
LLDP—IEEE standard, 802.1AB into its infrastructure
products. LLDP was recently accepted as the standard open
protocol for discovering network topologies and information
concerning devices on the network.
LLDP promises to simplify troubleshooting of enterprise
networks and enhance the ability of network management
tools to discover and maintain accurate network topologies
in multi-vendor environments. It serves to reduce the
complexities and expenses involved with convergence
driven network changes by greatly simplifying management
and connectivity issues. The new standard sets the stage for
convergence applications by allowing enterprises to add
new access devices in a non-disruptive Plug-and-Play
fashion. Voice and wireless services can be easily implemented
without major network upgrades.
.
Extreme Networks Technical Brief
Today’s networks must incorporate best-of-breed solutions
at every layer of the network, regardless of which vendor
you choose. LLDP allows enterprises to build a best-ofbreed
open converged network that can easily accommodate
new applications, such as voice, while achieving five 9’s
availability. The open nature of LLDP forms a foundation for
co-development of new add-on discovery features that will
help enable new Ethernet-based applications and services
in the future.
Extreme Networks employs LLDP not only as a means to
simplify deployment of access devices, but also as a
troubleshooting and firmware management tool and
eventually as a way to legitimize new data services. For
instance, in the future, Extreme Networks plans to provide
much-needed E911 emergency call services in Voice-over-IP
(VoIP) applications and enable new applications such as
Voice over WLAN (VoWLAN).
Benefits
The business level benefits that can be realized from
deploying LLDP in an Extreme Networks device are
far-reaching.
Lower Operating Costs
Increases in automation achieved through LLDP can
directly contribute to lower operating costs. Management
and network maintenance are greatly simplified as a result
of management tool consolidation and automation of
diagnostic and consistency checking procedures. Automated
discovery of access devices also reduce general setup costs
of new equipment. LLDP simplifies management and
network deployment, and as a result, lessens the number
and complexity of processes and reduces headcount.
Improved Choice and Flexibility in Network
Design
LLDP helps create an open market and customer choice so
that a business can choose the best vendor for a particular
network application. LLDP helps eliminate the barriers to
creating a multi-vendor best-of-breed solution, thus
allowing for a more advanced network and reduced capital
expenditures due to competitive bidding and increased
bargaining power. Open standards benefit the end customer
as a result of vendors co-developing technology. This
coordination simultaneously advances development cycles
on new technology and increases price competition.
© 2006 Extreme Networks, Inc. All rights reserved. Link Layer Discovery Protocol—Page 1

How LLDP Works
LLDP is essentially a neighbor discovery protocol that
defines a method for network access devices using Ethernet
connectivity to advertise information about them to peer
devices on the same physical LAN and store information
about the network. It allows a device to learn higher layer
management reachability and connection endpoint information
from adjacent devices. LLDP has been fully implemented
in Extreme Networks switches and is accessible from the
EPICenter ® management system.
Using LLDP, an Extreme Networks device is able to
advertise its own identification information, its capabilities
and media-specific configuration information, as well as
learn the same information from the devices connected to
it. LLDP advertises this information over Logical Link-Layer
Control frames and the information received from other
agents in IEEE-defined Management Information Bases
(MIB) modules. Figure 1 shows this relationship.
Port Device Info
A13 Switch xxxx
C2
D2
F3
Discovery MIB
IP Phone
PC
IP-PBX
xxxx
xxxx
xxxx
BlackDiamond ®
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BlackDiamond
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Intellegent Core
PSTN
LLDP—How it Works
The IEEE 802.1ab Link Layer Discovery Protocol defines a
standard way for Ethernet devices to advertise information
about themselves to their network neighbors and store
information they discover from other device.
1.
2.
3.
Figure 1: LLDP Peer Discovery
LAN switch and router advertise chassis/port ids and
system descriptions to each other.
The devices store the information they learn about each
other in local MIB databases accessible via SNMP.
A network management system (Extreme Networks
EPICenter) retrieves the data stored by each device that
builds a network topology map.
OSI Reference
Model Layers
Application
Presentation
Session
Transport
Network
Data Link
Physical
IEEE 802 Model Layer
Higher Protocol Layers
MAC Client {Bridge Relay Entity, LLC, etc.}
Link Aggregation Sublayer (Optional)
LLDP
MAC Control
(Optional)
MAC
Extreme Networks Technical Brief
LLDP significantly aids in the deployment of any network
device that supports the protocol. As a media independent
protocol intended to be run on all IEEE 802 devices, LLDP
may be used to discover routers, bridges, repeaters, WLAN
APs, IP telephones, network camera or any LLDP-enabled
device, regardless of manufacturer. Since LLDP runs over the
data-link layer only, an Extreme Networks switch running
one network layer protocol can discover and learn about an
access device running a different network layer protocol.
LLDP Architecture
LLDP is a data-link layer protocol, operating above the MAC
service layer and, as a result, can be used in any networking
device that implements a MAC service. Figure 2 shows
where LLDP resides in the IEEE 802 Model Layers.
LLDP LLDP
MAC Control
(Optional)
MAC Control
(Optional)
MAC MAC
Physical Physical Physical
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© 2006 Extreme Networks, Inc. All rights reserved. Link Layer Discovery Protocol—Page 2
Router
MIB
Network
Management
System
`
Figure 2: LLDP Architecture
3
2
1
LAN Switch
MIB
IP Phone

LLDP will advertise and store messages and will not solicit
information or keep state between devices. Each
Extreme Networks switch configured with an active LLDP
agent will send and receive messages on all physical
interfaces enabled for LLDP transmission. These messages
are sent periodically and are typically configured for short
time intervals to ensure that accurate information is always
available. These messages are then stored for a configurable
period of time, determined by the time-to-live (TTL) value
set by a user and contained within the received packet. The
message information expires and is discarded when the TTL
value is met. There is a default recommended time value for
the TTL of 120 seconds. The only other time an advertisement
would be sent is when a relevant change takes place
in the switch. If information values change for any reason,
the LLDP agent will be notified and will send out and
update the new values.
Basic LLDP functionality is represented in Figure 3.
STACK NO
STACK NO
LLDP
Summit X450
Advertisements
Summit X450
11 22 3 44 55 66 77 88 99 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24
11 22 33 44 55 66 77 88 99 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24
CONSOLE CONSOLE
CONSOLE CONSOLE
MIB MIB
SNMP
Advertisements
In this example LLDP advertisements are exchanged
between participating network devices and stored in the
MIB. As a result, EPICenter is able to gain access to that
information using SNMP and build a complete topology and
detailed inventory of network devices. These is true even if
some network devices, such as IP phones, only advertise
messages and are not able to store peer information.
Protocol Data Unit Format
`
A single LLDP Protocol Data Unit (LLDP PDU) is transmitted
in a single 802.3 Ethernet frame. The basic LLDP PDU
consists of a header, followed by a variable number of
information elements known as TLVs that each includes fields
for Type, Length, and Value. ‘Type’ identifies what kind of
information is being sent. ‘Length’ indicates the length of the
information string. ‘Value’ is the actual information sent.
Each LLDP PDU includes three mandatory TLVs followed by
optional TLVs. The three mandatory TLVs are Chassis ID,
Port ID and TTL. Other TLVs are optional to advertise. For
STACK NO
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1 22 33 44 55 66 77 88 99 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24
11 2 3 4 5 66 7 8 9 10 10 11 11 12 12 13 13 14 14 15 15 16 16 17 17 18 18 19 19 20 20 21 21 22 22 23 23 24 24
EPICenter
Network Management
Figure 3: Basic LLDP Functionality
CONSOLE CONSOLE
CONSOLE CONSOLE
Extreme Networks Technical Brief
Extreme Networks switch ports enabled with basic LLDP, the
information shown in Table 1 can be transmitted and stored
using LLDP.
Chassis ID
© 2006 Extreme Networks, Inc. All rights reserved. Link Layer Discovery Protocol—Page 3
Port ID
TLV
Time-to-live (TTL)
Port description
System name
System description
System capabilities
Management
address
Organizationally
specific
End of LLDP PDU
DESCRIPTION
Represents the chassis identification for the
device that transmitted the LLDP frame. The
receiving LLDP agent combines the Chassis ID
and Port ID to represent the entity connected
to the port where the frame was received.
Represents the identification of the specific
port that transmitted the LLDP frame. The
receiving LLDP agent combines the Chassis ID
and Port to represent the entity connected to
the port where the frame was received.
Represents the length of time that information
contained in the receive LLDP frame shall
be valid. If a value of zero is sent it can also
identify a device that has shut down or is no
longer transmitting, prompting deletion of the
record from the local database.
Identifies information about the interface. This
will include the name of the manufacturer, the
product name and the version of the interface
hardware/software (per RFC2863).
Identifies the administratively-assigned name
for the device (per RFC3418).
A textual description of the device. This value
typically includes the full name and version
identification of the system’s hardware type,
software operating-system, and networking
software (per RFC3418).
Identifies the capabilities of the device and its
primary function. (e.g. Repeater, Bridge, WLAN
Access Point, Router, Telephone, DOCSIS cable
device, Station only, etc.).
Identifies the IP address or MAC address of
the device.
The IEEE has further enhanced the value of the
LLDP protocol by making it possible for other
standards organizations and vendors to create
custom advertisement messages for other types
of endpoints. For Extreme Networks switches, the
following TLV based information is maintained:
- 802.1 VLAN extensions
- 802.3 LAN interface extensions
- LLDP-MED extensions
Marks the end of data. No further processing
of TLVs after this is necessary. This is a
mandatory TLV and must therefore be present
at the end of the data stream.
Table 1: Basic TLVs supported by Extreme Networks

Organizationally-Specific TLVs
Extreme Networks implementation of organizationallyspecific
TLVs represent a commitment to fully enabling the
network for converged applications and provide level of
functionality beyond that of most equipment vendors.
Organizationally-specific TLV extensions simplify the
integration of multi-vendor access networks by assisting in
the detection and configuration of IEEE 802.1 and IEEE
802.3 information. Additionally, standards organizations as
well as vendors such as Extreme Networks will help to drive
new functionality in LLDP extensions. New standards, such
as LLDP-Media Endpoint Discovery (MED), will provide
extensibility to fully standardized solutions to other reasonably
predictable needs in this area, as well as allowing for
vendor-specific extensions.
802.1 Extensions
IEEE 802.1 extensions deal primarily with describing VLAN
attributes. They will also be supported in the first release of
LLDP support on Extreme Networks switches. Supported
802.1 extensions are the TLVs shown in Table 2.
TLV
Port VLAN ID
Port & Protocol
VLAN ID
VLAN Name
Protocol Identity
802.3 Extensions
The IEEE 802.3 TLV extensions describe various attributes
associates with the operation of an 802.3 LAN interface. The
defined TLVs supported in the first implementation of LLDP
are shown in Table 3.
TLV
MAC/PHY
Configuration
and Status
Power-via-MDI
Link Aggregation
Maximum Frame
Size
DESCRIPTION
Identifies the VLAN identifier associated
with an untagged VLAN. Only one Port
VLAN ID can exist in an LLDP PDU.
Allows the port to advertise if it supports
port/protocol based VLANs, and there
associated VLAN ID.
Allows a device to advertise the textual name
of any VLAN with which it is configured.
Provides the protocols that are accessible
through the LLDP port.
Table 2: LLDP 802.1 Extensions
DESCRIPTION
Determines more about the auto negotiation
settings of the port, as well as the type of
physical interface used.
Advertises the power-via-MDI implementations
supported by the port. Power Information
allows for improved power management
for endpoints utilizing IEEE 802.3af Power
over Ethernet (PoE).
Allows the port to send information about its
configured link aggregation (whether the link
is capable of being aggregated, whether it is
currently in an aggregation and if in an ag-gregation,
the port of the aggregation).
Reports the maximum supported frame size
for the port.
Table 3: LLDP 802.3 Extensions
LLDP-MED
Extreme Networks Technical Brief
LLDP-MED is a new set of standards enhancing the basic
LLDP protocol, which applies to increased discovery of end-
point devices. In the future, Extreme Networks will implement
many of the new LLDP-MED standards under development
by the Telecommunications Industry Association (TIA).
Management Components
EPICenter Management
LLDP provides detailed Layer 2 network information for
connected access devices, exposing the entire LAN to the
EPICenter management system. Layer 2 discovery drills
down to the port that access devices are connected to and
gives a complete understanding of connectivity and device
properties. This granularity of detail is necessary to configure
and maintain end-to-end networks from a network management
system—“End-to-end,” meaning that network administrators
should not have to manually audit a network to
discover third-party vendor devices. Instead, LLDP allows for
centralized management and automated discovery of all
wired and wireless devices. This is achieved through flexible
management views, with options that can be selected per
device, user, action, time or location.
Using LLDP in Extreme Networks devices, EPICenter
manager is able to build a complete topology of the network
and make automation a reality. Because LLDP messages are
stored in the MIB of an Extreme Networks switch, EPICenter
is able to obtain complete access to the information through
SNMP advertisements. Having this control and information
availability through EPICenter allows centralized access to
accurate and timely network data, enabling simplified device
management and troubleshooting. For example, it becomes
possible for EPICenter management to discover configuration
inconsistencies or malfunctions that can result in impaired
communication at higher layers. Most importantly, EPICenter
can obtain this information from all network devices, not just
Extreme Networks devices.
Command Line Interface (CLI)
CLI is an optional method of configuration for LLDP. CLI
can send configuration information per port to
Extreme Networks switches via SNMP. CLI can also be
used to maintain a list of LLDP enabled ports and the
port mode (i.e. transmit only, receive only or transmit
and receive).
© 2006 Extreme Networks, Inc. All rights reserved. Link Layer Discovery Protocol—Page 4

Applications
Diagnostics/Troubleshooting
LLDP is a natural diagnostic tool because of its inherent
ability to discover and maintain accurate and up-to-date
network topologies. The TLV information exposes network
mapping, inventory data and network troubleshooting
information that may otherwise be unavailable. Network
administrators can use this information to identify outdated
hardware and software, speed and duplex mismatches and
improperly configured devices. For example, using TTL
values, LLDP can be used to locate ports that are no longer
sending LLDP advertisements to determine endpoint devices
that have gone out of service.
Voice
VoIP continues to demand availability standards and
advanced functionality from data networks that will help put
it on par with TDM systems. LLDP takes another step
forward in achieving this goal by facilitating multi-vendor IP
Telephony networks and enabling these networks to achieve
dial-tone reliability. VoIP networks have been relatively slow
to adopt voice-class features and have lacked complete
integration with existing network management systems. IP
telephones typically lack support of management protocols
such as SNMP, prohibiting NMS systems from a complete
network view. LLDP now brings discovery of VoIP topology
information to Extreme Networks Management System.
LLDP allows an IP phone to be dynamically and fully
recognized by an Extreme Networks device. The Extreme
Networks device is then able to adapt to the network
according to the needs of the IP telephone and MIB information
becomes accessible to EPICenter.
Extreme Networks acts as an industry innovator by
incorporating early-standards LLDP-MED functions and by
making significant headway in building Plug-and-Play IP
Telephony networks.
Extreme Networks LLDP
Implementation vs. Other
Discovery Protocols
Many network equipment vendors have developed discovery
protocols to operate in homogeneous networks comprised of
their own equipment. Cisco Systems has Cisco Discovery
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and North America
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Extreme Networks Technical Brief
Protocol (CDP); Enterasys Networks, Cabletron Discovery Protocol
(CDP); and Nortel Networks, Nortel Discovery Protocol (NDP).
However, many network architects building out enterprise and
carrier VoIP networks would like a standard means of discovery
allowing them to mix best-of-breed equipment from multiple vendors.
Most network designs are moving to a best-of-breed
strategy where individual components in the network are chosen
for their unique ability to handle an application. A standardsbased
discovery protocol readies a network for convergence
applications without major dependencies concerning the
manufacturer of network equipment. See Figure 4 for a comparison
between discovery protocols.
Industry Standards Based
Multi-Vendor Network Support
Chassis & Port ID
Port Description
System Name
System Description
System Capabilities
Management Address
VLAN ID
Voice VLANs
Network Policy
Auto Negotiation Requirements
Power Information (PoE Capable)
Frame Size Requirements
Location Advertisements (E911 capable)
Europe, Middle East, Africa
and South America
Phone +31 30 800 5100
Asia Pacific
Phone +852 2517 1123
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© 2006 Extreme Networks, Inc. All rights reserved.
Extreme Networks, the Extreme Networks Logo, BlackDiamond and EPICenter, are either registered trademarks or trademarks of
Extreme Networks, Inc. in the United States and/or other countries.
Specifications are subject to change without notice.
Japan
Phone +81 3 5842 4011
1061_01 11/06 Link Layer Discovery Protocol Technology Brief
LLDP-MED
Cisco CDP
Nortel NDP
Figure 4: Competitive Discovery Methods
Enterasys CDP