Link Layer Discovery Protocol (LLDP)

Transcription

1 Extreme etworks Technical Brief Link Layer Discovery Protocol () A ew Standard for Discovering and Managing Converged etwork 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 00 to 00 (IDC Research, 00). This exponential growth in the number of devices requiring LA 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 () used with Simple etwork Management Protocol (SMP). 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 etworks simplifies today s expanding network environment and management challenges by improving intelligence and automation throughout the network. Extreme etworks now incorporates the recently finalized IEEE standard, 0.AB into its infrastructure products. was recently accepted as the standard open protocol for discovering network topologies and information concerning devices on the network. 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.. Today s networks must incorporate best-of-breed solutions at every layer of the network, regardless of which vendor you choose. allows enterprises to build a best-ofbreed open converged network that can easily accommodate new applications, such as voice, while achieving five s availability. The open nature of 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 etworks employs 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 etworks plans to provide much-needed E emergency call services in Voice-over-IP (VoIP) applications and enable new applications such as Voice over WLA (VoWLA). Benefits The business level benefits that can be realized from deploying in an Extreme etworks device are far-reaching. Lower Operating Costs Increases in automation achieved through 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. simplifies management and network deployment, and as a result, lessens the number and complexity of processes and reduces headcount. Improved Choice and Flexibility in etwork Design helps create an open market and customer choice so that a business can choose the best vendor for a particular network application. 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. 00 Extreme etworks, Inc. All rights reserved. Link Layer Discovery Protocol Page

2 ` Extreme etworks Technical Brief How Works 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 LA and store information about the network. It allows a device to learn higher layer management reachability and connection endpoint information from adjacent devices. has been fully implemented in Extreme etworks switches and is accessible from the EPICenter management system. Using, an Extreme etworks 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. advertises this information over Logical Link-Layer Control frames and the information received from other agents in IEEE-defined Management Information Bases () modules. Figure shows this relationship. 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 0 devices, may be used to discover routers, bridges, repeaters, WLA APs, IP telephones, network camera or any -enabled device, regardless of manufacturer. Since runs over the data-link layer only, an Extreme etworks switch running one network layer protocol can discover and learn about an access device running a different network layer protocol. Architecture is a data-link layer protocol, operating above the service layer and, as a result, can be used in any networking device that implements a service. Figure shows where resides in the IEEE 0 Model Layers. OSI Reference Model Layers IEEE 0 Model Layer BlackDiamond 00 Application Higher Protocol Layers Discovery Port Device Info A Switch Intellegent Core PST Presentation Session Transport Client {Bridge Relay Entity, LLC, etc.} Link Aggregation Sublayer C D F IP Phone PC IP-PBX etwork Data Link Control Control Control Physical Physical Physical Physical BlackDiamond 0 Figure : Architecture Figure : Peer Discovery How it Works The IEEE 0.ab 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. Router LA Switch IP Phone. LA 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 databases accessible via SMP. A network management system (Extreme etworks EPICenter) retrieves the data stored by each device that builds a network topology map. etwork Management System BlackDiamond 0 00 Extreme etworks, Inc. All rights reserved. Link Layer Discovery Protocol Page

3 Extreme etworks Technical Brief will advertise and store messages and will not solicit information or keep state between devices. Each Extreme etworks switch configured with an active agent will send and receive messages on all physical interfaces enabled for 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 0 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 agent will be notified and will send out and update the new values. Extreme etworks switch ports enabled with basic, the information shown in Table can be transmitted and stored using. Chassis ID Port ID Represents the identification of the specific port that transmitted the frame. The receiving agent combines the Chassis ID and Port to represent the entity connected to the port where the frame was received. Time-to-live (TTL) Represents the length of time that information contained in the receive 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. Port description 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 RFC). System name Identifies the administratively-assigned name for the device (per RFC). System description 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 RFC). System capabilities Identifies the capabilities of the device and its primary function. (e.g. Repeater, Bridge, WLA Access Point, Router, Telephone, DOCSIS cable device, Station only, etc.). Management address Identifies the IP address or address of the device. Organizationally specific The IEEE has further enhanced the value of the protocol by making it possible for other standards organizations and vendors to create custom advertisement messages for other types of endpoints. For Extreme etworks switches, the following based information is maintained: - 0. VLA extensions - 0. LA interface extensions - -MED extensions End of PDU Marks the end of data. o further processing of s after this is necessary. This is a mandatory and must therefore be present at the end of the data stream. Basic functionality is represented in Figure. Advertisements Summit X0 0 0 Summit X0 STACK O STACK O COSOLE 0 0 DESCRIPTIO Represents the chassis identification for the device that transmitted the frame. The receiving agent combines the Chassis ID and Port ID to represent the entity connected to the port where the frame was received. COSOLE STACK O STACK O COSOLE COSOLE SMP Advertisements ` EPICenter etwork Management Figure : Basic Functionality In this example advertisements are exchanged between participating network devices and stored in the. As a result, EPICenter is able to gain access to that information using SMP 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 Table : Basic s supported by Extreme etworks A single Protocol Data Unit ( PDU) is transmitted in a single 0. Ethernet frame. The basic PDU consists of a header, followed by a variable number of information elements known as s 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 PDU includes three mandatory s followed by optional s. The three mandatory s are Chassis ID, Port ID and TTL. Other s are optional to advertise. For 00 Extreme etworks, Inc. All rights reserved. Link Layer Discovery Protocol Page

4 Extreme etworks Technical Brief Organizationally-Specific s Extreme etworks implementation of organizationallyspecific s represent a commitment to fully enabling the network for converged applications and provide level of functionality beyond that of most equipment vendors. Organizationally-specific extensions simplify the integration of multi-vendor access networks by assisting in the detection and configuration of IEEE 0. and IEEE 0. information. Additionally, standards organizations as well as vendors such as Extreme etworks will help to drive new functionality in extensions. ew standards, such as -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. 0. Extensions IEEE 0. extensions deal primarily with describing VLA attributes. They will also be supported in the first release of support on Extreme etworks switches. Supported 0. extensions are the s shown in Table. Port VLA ID Port & Protocol VLA ID VLA ame Protocol Identity DESCRIPTIO 0. Extensions The IEEE 0. extensions describe various attributes associates with the operation of an 0. LA interface. The defined s supported in the first implementation of are shown in Table. /PH Configuration and Status Power-via-MDI Link Aggregation Maximum Frame Size Identifies the VLA identifier associated with an untagged VLA. Only one Port VLA ID can exist in an PDU. Allows the port to advertise if it supports port/protocol based VLAs, and there associated VLA ID. Allows a device to advertise the textual name of any VLA with which it is configured. Provides the protocols that are accessible through the port. Table : 0. Extensions DESCRIPTIO 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 0.af 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 : 0. Extensions -MED -MED is a new set of standards enhancing the basic protocol, which applies to increased discovery of endpoint devices. In the future, Extreme etworks will implement many of the new -MED standards under development by the Telecommunications Industry Association (TIA). Management Components EPICenter Management provides detailed Layer network information for connected access devices, exposing the entire LA to the EPICenter management system. Layer 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, 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 in Extreme etworks devices, EPICenter manager is able to build a complete topology of the network and make automation a reality. Because messages are stored in the of an Extreme etworks switch, EPICenter is able to obtain complete access to the information through SMP 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 etworks devices. Command Line Interface (CLI) CLI is an optional method of configuration for. CLI can send configuration information per port to Extreme etworks switches via SMP. CLI can also be used to maintain a list of enabled ports and the port mode (i.e. transmit only, receive only or transmit and receive). 00 Extreme etworks, Inc. All rights reserved. Link Layer Discovery Protocol Page

5 Extreme etworks Technical Brief Applications Diagnostics/Troubleshooting is a natural diagnostic tool because of its inherent ability to discover and maintain accurate and up-to-date network topologies. The information exposes network mapping, inventory data and network troubleshooting information that may otherwise be unavailable. etwork administrators can use this information to identify outdated hardware and software, speed and duplex mismatches and improperly configured devices. For example, using TTL values, can be used to locate ports that are no longer sending 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. 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 SMP, prohibiting MS systems from a complete network view. now brings discovery of VoIP topology information to Extreme etworks Management System. allows an IP phone to be dynamically and fully recognized by an Extreme etworks device. The Extreme etworks device is then able to adapt to the network according to the needs of the IP telephone and information becomes accessible to EPICenter. Extreme etworks acts as an industry innovator by incorporating early-standards -MED functions and by making significant headway in building Plug-and-Play IP Telephony networks. Extreme etworks Implementation vs. Other Discovery Protocols Protocol (CDP); Enterasys etworks, Cabletron Discovery Protocol (CDP); and ortel etworks, ortel Discovery Protocol (DP). 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 for a comparison between discovery protocols. Industry Standards Based Multi-Vendor etwork Support Chassis & Port ID Port Description System ame System Description System Capabilities Management Address VLA ID Voice VLAs etwork Policy Auto egotiation Requirements Power Information (PoE Capable) Frame Size Requirements Location Advertisements (E capable) -MED Cisco CDP ortel DP Figure : Competitive Discovery Methods Enterasys CDP Many network equipment vendors have developed discovery protocols to operate in homogeneous networks comprised of their own equipment. Cisco Systems has Cisco Discovery com info@extremenetworks. Corporate and orth America Extreme etworks, Inc. Monroe Street Santa Clara, CA 0 USA Phone Europe, Middle East, Africa and South America Phone Asia Pacific Phone + Japan Phone Extreme etworks, Inc. All rights reserved. Extreme etworks, the Extreme etworks Logo, BlackDiamond and EPICenter, are either registered trademarks or trademarks of Extreme etworks, Inc. in the United States and/or other countries. Specifications are subject to change without notice. 0_0 /0 Link Layer Discovery Protocol Technology Brief