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Link Layer Discovery Protocol

Emergency Services Workshop, NY

Oct 5-6, 2006

Manfred Arndt (manfred.r.arndt@hp.com)

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Scope

IEEE 802.1AB Link Layer Discovery Protocol (LLDP)

A standard and extensible multi-vendor protocol and managementelements to support network topology discovery and exchange

device configuration and capabilitiesDeveloped and maintained by IEEE 802.1, planned for revision

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Objectives

Widespread industry adoptionSimple and leveraged design increases chances of vendor adoption

Simple design leads to low development cost

Interoperability with many endpoint device types

Low complexity higher interoperability potential

Must be practical for both cost-restrained and feature rich endpoints

High reliability, critical to Emergency Call Service scenarios

Low complexity with fewest possible moving parts

Location always provided immediately on connection of move

Easily extensible for future needs

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LLDP Overview

Basic Functions (IEEE 802.1AB-2005*):

Simple one-way neighbor discovery protocol with periodic transmissions

LLDP frames are not forwarded, but constrained to a single point to point link

LLDP frames contain formatted TLVs (type, length, value)

Globally unique system and port identification

Time-to-Live information for ageing purposes

Optional system capabilities (e.g. router, IP phone, wireless AP)

Optional system name, description, and management address

Organizational extensions

Receiver stores information in a neighbor database, accessible via SNMP MIB

Receiver ages MIB to

insure only valid network data is available

Management applications can harness the power via SNMP

* Currently planned for revision, PAR submitted for targeted Nov 06 approval

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All LLDP Entities contain1 or more LLDP Agents

LLDP operates above theMAC Service Layer

LSAP = Link service access point

MSAP = MAC service access point

LLDP Entities & AgentsA peak under the hood*

Local MIBs: Holds locally

configured data Data may be

supplied/modifiedby managementapplications

Remote MIBs: Holds and ages received data

from far end Available for management

applications use

Entity Management MIBs: Common data, of use to

LLDP and others Not directly part of LLDP

LLDP State machine Controls Tx and Rx of frames Contains state machine control

variables

* Animated Slide

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Easy to define organizational extensions

There are currently three organizational extensions:

1. IEEE 802.1

Port VLAN, Port & Protocol VLANs, VLAN Name, Protocol Entity2. IEEE 802.3

MAC/PHY configuration, PoE Power, Link Aggregation, Maximum Frame Size

3. TIA - IP Telephony Infrastructure (LLDP-MED)

VLAN & QoS auto-config, Physical Location Discovery, Detailed Inventory, Fine Grain PoE Power

LLDP TLV Extensibility

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802.1AB Revision Proposal (Nov 06)

Currently planned project revision considerations include: Supporting the needs of 802.3at (PoE Plus), including:

Ongoing dynamic fine-grain power negotiation (e.g. video call in process)

Power priority (e.g. must keep red phone alive)

Backup power conservation (e.g. extend UPS battery life during disasters)

Provide support for rapid fast start TLV exchange

Required for power negotiation and to quickly discover Audio Visual Bridgeand Congestion Management interconnectivity boundaries

Define additional destination addresses such that the propagation of

LLDP frames across specific transparent devices can be achieved Certain TLVs, like PoE power and speed/duplex, must never be forwarded

Some TLVs need to traverse transparent links (e.g. across provider bridges)

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References & Contacts

The formal LLDP specification is freely available for download at:

http://standards.ieee.org/getieee802/download/802.1AB-2005.pdf

Useful links:

http://en.wikipedia.org/wiki/LLDP

http://wiki.ethereal.com/LinkLayerDiscoveryProtocol

Contacts:

Paul Congdon (paul.congdon@hp.com); project leader of IEEE 802.1AB-2005 (LLDP)and vice-chair of IEEE 802.1 Working Group

Manfred Arndt (manfred.r.arndt@hp.com); co-author of ANSI/TIA-1057 (LLDP-MED)

http://standards.ieee.org/getieee802/download/802.1AB-2005.pdfhttp://en.wikipedia.org/wiki/LLDPhttp://wiki.ethereal.com/LinkLayerDiscoveryProtocolmailto:paul.congdon@hp.commailto:manfred.r.arndt@hp.commailto:manfred.r.arndt@hp.commailto:paul.congdon@hp.comhttp://wiki.ethereal.com/LinkLayerDiscoveryProtocolhttp://en.wikipedia.org/wiki/LLDPhttp://standards.ieee.org/getieee802/download/802.1AB-2005.pdfhttp://standards.ieee.org/getieee802/download/802.1AB-2005.pdfhttp://standards.ieee.org/getieee802/download/802.1AB-2005.pdf

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Backup Slides

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Discovery MIB

Discovery MIB

How Does LLDP Work?

PSTN

Im an

IP-PhoneIm a PC

Im anIP-Phone

Im an

IP-Phone

Im a

switch

Im a

switch

Im a VoIP Gateway / Server

Im a

switch Im a

switch

Im a

switch

Im a

switch

Im a

switch

port device info

A4 IP-phone xxxx

A4 PC xxxx

B6 PC xxxx

B21 Switch xxxx

port device info

A19 Switch xxxx

C2 IP-Phone xxxx

D2 IP-Phone xxxx

F3 VoIP Gateway xxxx

Im a PC

Im a PC

Management App

Topology discovery,

location, inventory &more

SNMP

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LLDP Frame Format

IEEE 802.3 LLDP frame format

LLDP Multicast = 01-80-C2-00-00-0E (same as Spanning Tree except for last octet)

LLDPDU format

Each TLV (Type, Length, Value) contains a set of useful attributes

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Is LLDP a stateless protocol?

IEEE 802.1AB-2005: LLDP updates are limited to no faster than 1 per second

Intended as one-way advertisements, without req / acks

Dramatically simplifies implementations

Bounds performance requirements for scalability

On occasion, the management entity may see a change in state of apeer and perform some local database maintenance operation

By definition, anytime a local value changes, LLDP sends a frame thustriggering a packet in reverse (limited to once per second)

The protocol itself is stateless, but the management entity above isrequired to maintain state and may act on information from peers

LLDP-MED (ANSI/TIA-1057) follows these same principals.