Link Layer Topology Discovery (LLTD) is a proprietary

link layer In computer networking, the link layer is the lowest layer in the Internet protocol suite, the networking architecture of the Internet. The link layer is the group of methods and communications protocols confined to the link that a host is phys ...

protocol for

network topology Network topology is the arrangement of the elements (Data link, links, Node (networking), nodes, etc.) of a communication network. Network topology can be used to define or describe the arrangement of various types of telecommunication networks, ...

discovery and

quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...

diagnostics.

Microsoft Microsoft Corporation is an American multinational corporation and technology company, technology conglomerate headquartered in Redmond, Washington. Founded in 1975, the company became influential in the History of personal computers#The ear ...

developed it as part of the

Windows Rally Windows Rally is a set of technologies from Microsoft intended to simplify the setup and maintenance of wired and wireless network-connected devices. They aim to increase reliability and security of connectivity for users who connect the devices ...

set of technologies. The LLTD protocol operates over both wired (such as Ethernet (IEEE 802.3) or

power line communication Power-line communication (PLC) is the carrying of data on a conductor (the ''power-line carrier'') that is also used simultaneously for AC electric power transmission or electric power distribution to consumers. A wide range of power-line comm ...

) as well as wireless networks (such as

IEEE 802.11 IEEE 802.11 is part of the IEEE 802 set of local area network (LAN) technical standards, and specifies the set of medium access control (MAC) and physical layer (PHY) protocols for implementing wireless local area network (WLAN) computer com ...

). LLTD is included in

Windows 7 Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was Software release life cycle#Release to manufacturing (RTM), released to manufacturing on July 22, 2009, and became generally available on October 22, ...

Windows Vista Windows Vista is a major release of the Windows NT operating system developed by Microsoft. It was the direct successor to Windows XP, released five years earlier, which was then the longest time span between successive releases of Microsoft W ...

and

Windows 10 Windows 10 is a major release of Microsoft's Windows NT operating system. The successor to Windows 8.1, it was Software release cycle#Release to manufacturing (RTM), released to manufacturing on July 15, 2015, and later to retail on July 2 ...

. It is used by their ''Network Map'' feature to display a graphical representation of the

local area network A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, campus, or building, and has its network equipment and interconnects locally managed. LANs facilitate the distribution of da ...

(LAN) or

wireless LAN A wireless LAN (WLAN) is a wireless computer network that links two or more devices using wireless communication to form a local area network (LAN) within a limited area such as a home, school, computer laboratory, campus, or office building ...

(WLAN), to which the computer is connected.

Windows XP Windows XP is a major release of Microsoft's Windows NT operating system. It was released to manufacturing on August 24, 2001, and later to retail on October 25, 2001. It is a direct successor to Windows 2000 for high-end and business users a ...

does not contain the LLTD protocol as a standard component and as a result, Windows XP computers do not appear on the ''Network Map'' unless the LLTD responder is installed on Windows XP computers. LLTD is available for download for 32-bit editions of Windows XP with Service Pack 2 (as a publicly released update) and for Windows XP with Service Pack 3 (as a hotfix by request). LLTD Responder was not released for

Windows XP Professional x64 Edition Windows XP Professional x64 Edition is an edition of Microsoft's Windows XP operating system that supports the x86-64 architecture. It was released on April 25, 2005, alongside the x86-64 versions of Windows Server 2003. Windows XP Profession ...

. A 2006 fall update for the

Xbox 360 The Xbox 360 is a home video game console developed by Microsoft. As the successor to the Xbox (console), original Xbox, it is the second console in the Xbox#Consoles, Xbox series. It was officially unveiled on MTV on May 12, 2005, with detail ...

enabled support for the LLTD protocol. Being a link layer (or OSI Layer 2) implementation, LLTD operates strictly on a given local network segment. It cannot discover devices across routers, an operation which would require

Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP ...

level routing. Link Layer Topology Discovery in Windows Vista consists of two components. The LLTD Mapper I/O component is the master module which controls the discovery process and generates the Network Map. Appropriate permissions for this may be configured with

Group Policy Group Policy is a feature of the Microsoft Windows NT family of operating systems (including Windows 8.1, Windows 10, Windows 11) that controls the working environment of user accounts and computer accounts. Group Policy provides centralized mana ...

settings. It can be allowed or disallowed for domains, and private and public networks. The Mapper sends discovery command packets onto the local network segment via a raw network interface socket. The second component of LLTD are the LLTD Responders which answer Mapper requests about their host and possibly other discovered network information. In addition to illustrating the layout of a network with representative icons for the hosts and interconnecting lines, each device icon may be explored to produce a popup information box summarizing important network and host parameters, such as

MAC address A MAC address (short for medium access control address or media access control address) is a unique identifier assigned to a network interface controller (NIC) for use as a network address in communications within a network segment. This use i ...

and

IP address An Internet Protocol address (IP address) is a numerical label such as that is assigned to a device connected to a computer network that uses the Internet Protocol for communication. IP addresses serve two main functions: network interface i ...

(both

IPv4 Internet Protocol version 4 (IPv4) is the first version of the Internet Protocol (IP) as a standalone specification. It is one of the core protocols of standards-based internetworking methods in the Internet and other packet-switched networks. ...

and

IPv6 Internet Protocol version 6 (IPv6) is the most recent version of the Internet Protocol (IP), the communication protocol, communications protocol that provides an identification and location system for computers on networks and routes traffic ...

). Icons are labeled with the hostnames (or first component of their

fully qualified domain name A fully qualified domain name (FQDN), sometimes also called an absolute domain name, is a domain name that specifies its exact location in the tree hierarchy of the Domain Name System (DNS). It specifies all domain levels, including the top-level ...

s), or a representative name of the function of the device, e.g., "gateway". If the device has reported the presence of a management Web interface, clicking on the icon will open a HTTP session to the host. The LLTD responder for Windows XP only supports reporting of IPv4 addresses and not IPv6. A

royalty free Royalty-free (RF) material subject to copyright or other intellectual property rights may be used without the need to pay royalties or license fees for each use, per each copy or volume sold or some time period of use or sales. Computer standards ...

Linux Linux ( ) is a family of open source Unix-like operating systems based on the Linux kernel, an kernel (operating system), operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically package manager, pac ...

sample implementation of the LLTD responder is available from Microsoft as part of the Windows Rally Development Kit. Using LLTD specifications requires signing a Microsoft Windows Rally license agreement. There also exists a

Perl Perl is a high-level, general-purpose, interpreted, dynamic programming language. Though Perl is not officially an acronym, there are various backronyms in use, including "Practical Extraction and Reporting Language". Perl was developed ...

implementation, using Net::Frame, available via

CPAN The Comprehensive Perl Archive Network (CPAN) is a software repository of over 220,000 software modules and accompanying documentation for 45,500 distributions, written in the Perl programming language by over 14,500 contributors. ''CPAN'' can de ...

References

{{Reflist, 2

External links

Download LLTD Responder for Windows XP

Link Layer Topology Discovery Protocol Specification
and license
Windows Rally Development Kit

LLTD scanner for Linux/FreeBSD
Link protocols Network protocols Windows communication and services Windows Vista

See also

References

External links