Link Layer Topology Discovery
Encyclopedia
Link Layer Topology Discovery (LLTD) is a proprietary Link Layer
protocol for network topology
discovery and quality of service
diagnostics. Microsoft
developed it as part of the Windows Rally
set of technologies. The LLTD protocol operates over both wired (such as Ethernet (IEEE 802.3)
or Power line communication
) as well as wireless networks (such as IEEE 802.11
).
LLTD is included in Windows Vista
and Windows 7. It is used by their Network Map feature to display a graphical representation of the local area network
(LAN) or wireless LAN
(WLAN), to which the computer is connected. Windows XP
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 is not released for Windows XP Professional x64 Edition
.
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
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
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
and IP address
(both IPv4
and IPv6
). Icons are labeled with the hostnames (or first component of their fully qualified domain names), 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, but not IPv6.
A royalty free
Linux
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
implementation, using Net::Frame, available via CPAN
Link Layer
In computer networking, the link layer is the lowest layer in the Internet Protocol Suite , the networking architecture of the Internet . It is the group of methods or protocols that only operate on a host's link...
protocol for network topology
Network topology
Network topology is the layout pattern of interconnections of the various elements of a computer or biological network....
discovery and quality of service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
diagnostics. Microsoft
Microsoft
Microsoft Corporation is an American public multinational corporation headquartered in Redmond, Washington, USA that develops, manufactures, licenses, and supports a wide range of products and services predominantly related to computing through its various product divisions...
developed it as part of the Windows Rally
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 to the Internet or to computers running Microsoft...
set of technologies. The LLTD protocol operates over both wired (such as Ethernet (IEEE 802.3)
Ethernet
Ethernet is a family of computer networking technologies for local area networks commercially introduced in 1980. Standardized in IEEE 802.3, Ethernet has largely replaced competing wired LAN technologies....
or Power line communication
Power line communication
Power line communication or power line carrier , also known as power line digital subscriber line , mains communication, power line telecom , power line networking , or broadband over power lines are systems for carrying data on a conductor also used for electric power transmission.A wide range...
) as well as wireless networks (such as IEEE 802.11
IEEE 802.11
IEEE 802.11 is a set of standards for implementing wireless local area network computer communication in the 2.4, 3.6 and 5 GHz frequency bands. They are created and maintained by the IEEE LAN/MAN Standards Committee . The base version of the standard IEEE 802.11-2007 has had subsequent...
).
LLTD is included in Windows Vista
Windows Vista
Windows Vista is an operating system released in several variations developed by Microsoft for use on personal computers, including home and business desktops, laptops, tablet PCs, and media center PCs...
and Windows 7. It is used by their Network Map feature to display a graphical representation of the local area network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
(LAN) or wireless LAN
Wireless LAN
A wireless local area network links two or more devices using some wireless distribution method , and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network...
(WLAN), to which the computer is connected. Windows XP
Windows XP
Windows XP is an operating system produced by Microsoft for use on personal computers, including home and business desktops, laptops and media centers. First released to computer manufacturers on August 24, 2001, it is the second most popular version of Windows, based on installed user base...
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 is not released for Windows XP Professional x64 Edition
Windows XP Professional x64 Edition
Microsoft Windows XP Professional x64 Edition released on April 25, 2005 is an edition of Windows XP for x86-64 personal computers. It is designed to use the expanded 64-bit memory address space provided by the x86-64 architecture....
.
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
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
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
Group Policy is a feature of the Microsoft Windows NT family of operating systems. Group Policy is a set of rules that control the working environment of user accounts and computer accounts. Group Policy provides the centralized management and configuration of operating systems, applications, and...
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
MAC address
A Media Access Control address is a unique identifier assigned to network interfaces for communications on the physical network segment. MAC addresses are used for numerous network technologies and most IEEE 802 network technologies, including Ethernet...
and IP address
IP address
An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...
(both IPv4
IPv4
Internet Protocol version 4 is the fourth revision in the development of the Internet Protocol and the first version of the protocol to be widely deployed. Together with IPv6, it is at the core of standards-based internetworking methods of the Internet...
and IPv6
IPv6
Internet Protocol version 6 is a version of the Internet Protocol . It is designed to succeed the Internet Protocol version 4...
). Icons are labeled with the hostnames (or first component of their fully qualified domain names), 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, but not IPv6.
A royalty free
Royalty free
Royalty-Free, or RF, refers to the right to use copyrighted material or intellectual property without the need to pay royalties for each use or per volume sold, or some time period of use or sales.-Computer standards:...
Linux
Linux
Linux is a Unix-like computer operating system assembled under the model of free and open source software development and distribution. The defining component of any Linux system is the Linux kernel, an operating system kernel first released October 5, 1991 by Linus Torvalds...
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
Perl is a high-level, general-purpose, interpreted, dynamic programming language. Perl was originally developed by Larry Wall in 1987 as a general-purpose Unix scripting language to make report processing easier. Since then, it has undergone many changes and revisions and become widely popular...
implementation, using Net::Frame, available via CPAN
CPAN
CPAN, the Comprehensive Perl Archive Network, is an archive of nearly 100,000 modules of software written in Perl, as well as documentation for it. It has a presence on the World Wide Web at and is mirrored worldwide at more than 200 locations...
See also
- Simple Network Management ProtocolSimple Network Management ProtocolSimple Network Management Protocol is an "Internet-standard protocol for managing devices on IP networks. Devices that typically support SNMP include routers, switches, servers, workstations, printers, modem racks, and more." It is used mostly in network management systems to monitor...
- Service DiscoveryService discoveryService discovery protocols are network protocols which allow automatic detection of devices and services offered by these devices on a computer network....
- Link Layer Discovery ProtocolLink Layer Discovery ProtocolThe Link Layer Discovery Protocol is a vendor-neutral Link Layer protocol in the Internet Protocol Suite used by network devices for advertising their identity, capabilities, and neighbors on a IEEE 802 local area network, principally wired Ethernet...
- same aim (and layer) but IEEE standard protocol. - Cisco Discovery ProtocolCisco Discovery ProtocolThe Cisco Discovery Protocol is a proprietary Data Link Layer network protocol developed by Cisco Systems. It is used to share information about other directly connected Cisco equipment, such as the operating system version and IP address...
- Similar end as LLTD which is clearly based on CDP. - Nortel Discovery ProtocolNortel Discovery ProtocolThe Nortel Discovery Protocol is a Data Link Layer network protocol for discovery of Nortel devices...