Carrier Ethernet
Encyclopedia
Carrier Ethernet is a marketing term for extensions to Ethernet
to enable telecommunications network providers ("common carriers" in US industry jargon) to provide Ethernet services to customers and to utilize Ethernet technology in their networks.
has a long history. It has become dominant in enterprise networks. This dominance has led to high production-volume components, which in turn have allowed extremely low cost per bit. Likewise Ethernet
has a long history of re-inventing itself. From the original copper coaxial cable
format ("thicknet
") it has extended its scope to nearly all copper, optical fiber
and wireless physical media
. Bit rate
s have continued to increase, traditionally growing tenfold each time a new rate is defined. Gigabit Ethernet
interfaces are widely deployed in PCs and servers, and 10 Gbit/s in local area network
(LAN) backbones.
Rates up to 100 Gigabit Ethernet
were standardized in 2010 and 2011.
Ethernet's dominance is partly attributed to the simple advantages for the industry of adopting a single standard to drive up volumes and drive down prices. In part, it is also due to ease of deployment, using its ability to self-configure itself based on the key concepts of “learning bridge”, (flooding, and associating learned destination addresses
with bridge ports) and "spanning tree protocol
," (the protocol used for avoiding bridging loops).
Historically, competing protocols and cabling have been created in order to access higher speed devices than contemporary Ethernet-connected devices handled at an affordable price. Examples include FireWire and Light Peak
. One motive to create competing standards has been to drive down the price of comparable-speed Ethernet devices. Once this purpose is achieved, competing standards tend to disappear or be confined to very specialized niches.
Ethernet is a fairly simple protocol which has scaled to hundreds of thousands of times faster speeds and consistently been able to adapt to meet the needs and demands of new markets. For example, time domain capabilities are being added to IEEE 802.3 Ethernet to support IEEE 802.1 audio/video bridging (AVB) , and these capabilities will be applicable to time sensitive carrier applications likewise IEEE 1588.
Customer LAN networks are increasingly connected to wide-area telecommunications networks over Ethernet interfaces or to devices that bridge DSL or wireless to these. Moreover, customers are familiar with the capabilities of Ethernet networks, and would like to extend these capabilities to multi-site networks. Meanwhile the needs of such networks have expanded to include many services previously handled only on the LAN or by specialized connections, notably video and backup. It is not practical to expand most small networks beyond 1G or at most 2G (dual teaming gigabit) capacity per segment, since the bottleneck remains in the wide area links to other offices and online services.
(WAN) and metropolitan area network
(MAN) providers find themselves with three needs:
They are also constrained as services cannot be migrated from local to wide area services too fast lest they exceed the total provisioning available and result in unacceptable quality. Services that try to expand too fast lose money while those that wait too long lose customers. Accordingly carriers must expand their services conservatively and pay close attention to Quality of Service
(QoS).
http://www.metroethernetforum.org. This played a key role in defining:
All these services provide standard definitions of such characteristics as bandwidth, resilience and service multiplexing, allowing customers to compare service offerings and facilitating service level agreement
s (SLAs). Analogous definitions for wireless networks are defined in IEEE 802.21
and IEEE 802.11u
, though these are intended for much shorter time commitments and services appropriate for mobile users only.
does not specify how Ethernet services are to be provided in a carrier network. Despite the advantages described above, Ethernet has traditionally had a number of limitations in the WAN application. The "bridge" and "spanning tree" concepts described above do not scale to large international networks. Moreover, Ethernet has lacked some of the dependability features necessary in this application (in particular, mechanisms to isolate one customer's traffic from another, to measure performance of a customer service instance, and to rapidly detect and repair failures in large networks).
Because of these limitations, and because of the need to make use of pre-existing equipment, Ethernet services have been carried across wide area networks using other technologies. Two types of technology have been widely used, while a third (Carrier-Ethernet transport) is rapidly emerging as a viable and logical option for Carrier-Ethernet services.
networks, making use of virtual concatenation (ITU-T G.707) and LCAS (Link Capacity Adjustment Scheme - ITU-T G.7042) to create an appropriate size carrier bundle, and of Generic Framebase of SDH equipment, and takes advantage of the management and recovery features of SDH to provide high availability
and resilience to failures.
/MPLS
networks making use of a wide range of IP-related protocols
(see IETF pseudowire standards, e.g. RFC 3985, RFC 4448). Ethernet links are transported as “pseudowires” using MPLS
label switched path
s (LSPs) inside an outer MPLS “tunnel”. This strategy can support both point-to-point (Virtual Private Wire Service - VPWS) and multipoint (Virtual Private LAN service - VPLS) services, and has recently achieved significant deployment in routed networks. It makes use of a number of basic transport protocols, including SDH and (increasingly) Ethernet.
.
Carrier Ethernet demarcation devices are required to support services, such as EPL (Ethernet Private Line), EVPL (Ethernet Virtual Private Line), E-LAN (Ethernet LAN), and E-Tree (Ethernet Tree), as specified by the MEF (Metro Ethernet Forum). Such support needs to include SLA (service level agreement) management capabilities, with consistent performance over fiber, DSL, bonded PDH, and SDH/SONET access lines. As a result, must-have Carrier Ethernet demarcation features include sophisticated traffic management and hierarchical QoS (quality of service) mechanisms, standard end-to-end OAM (operations, administration and maintenance) and performance monitoring, extensive fault management and diagnostics, and SDH/SONET-like resiliency to reduce service provider operating costs and capital expenses.
The key roles have been played by the Institute of Electrical and Electronic Engineers (IEEE) 802.1 and 802.3 standards committees. IEEE 802.1 has addressed the scalability and management issues in the standards for Provider Bridges (802.1ad) and Provider Backbone Bridges (802.1ah). These standards allow for Ethernet networks of planetary scale. Associated standards (IEEE 802.1ag, and related ITU-T standard Y.1731) provide Operations and Maintenance (OAM) capabilities allowing connectivity verification, rapid recovery, and performance measurement. Current work on PBB-TE (802.1Qay: Provider Backbone Bridging-Traffic Engineering) is allowing such an Ethernet to be controlled by an external control or management application (for example, a network management application or a transport control plane such as GMPLS (IETF RFC 3945)), so as to allow the full range of traffic engineering policies and strategies to a network provider.
The IEEE 802.3 Working Group in close cooperation with the ITU
have been working to simplify the transport of 40G and 100G technologies being developed by both bodies: 802.3 for LAN and ITU for the OTN
. The OIF
and the Ethernet Alliance
have also been working cooperatively with their members to enable future enhancements to Ethernet for the WAN while looking to the future speed of Ethernet technologies and services.
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....
to enable telecommunications network providers ("common carriers" in US industry jargon) to provide Ethernet services to customers and to utilize Ethernet technology in their networks.
Background
EthernetEthernet
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....
has a long history. It has become dominant in enterprise networks. This dominance has led to high production-volume components, which in turn have allowed extremely low cost per bit. Likewise Ethernet
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....
has a long history of re-inventing itself. From the original copper coaxial cable
Coaxial cable
Coaxial cable, or coax, has an inner conductor surrounded by a flexible, tubular insulating layer, surrounded by a tubular conducting shield. The term coaxial comes from the inner conductor and the outer shield sharing the same geometric axis...
format ("thicknet
10BASE5
10BASE5 was the original commercially available variant of Ethernet.For its physical layer it used cable similar to RG-8/U coaxial cable but with extra braided shielding. This is a stiff, diameter cable with an impedance of 50 ohms , a solid center conductor, a foam insulating filler, a shielding...
") it has extended its scope to nearly all copper, optical fiber
Optical fiber
An optical fiber is a flexible, transparent fiber made of a pure glass not much wider than a human hair. It functions as a waveguide, or "light pipe", to transmit light between the two ends of the fiber. The field of applied science and engineering concerned with the design and application of...
and wireless physical media
Wireless network
Wireless network refers to any type of computer network that is not connected by cables of any kind. It is a method by which homes, telecommunications networks and enterprise installations avoid the costly process of introducing cables into a building, or as a connection between various equipment...
. Bit rate
Bit rate
In telecommunications and computing, bit rate is the number of bits that are conveyed or processed per unit of time....
s have continued to increase, traditionally growing tenfold each time a new rate is defined. Gigabit Ethernet
Gigabit Ethernet
Gigabit Ethernet is a term describing various technologies for transmitting Ethernet frames at a rate of a gigabit per second , as defined by the IEEE 802.3-2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local networks where it performed...
interfaces are widely deployed in PCs and servers, and 10 Gbit/s in 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) backbones.
Rates up to 100 Gigabit Ethernet
100 Gigabit Ethernet
40 Gigabit Ethernet, or 40GbE, and 100 Gigabit Ethernet, or 100GbE, are high-speed computer network standards developed by the Institute of Electrical and Electronics Engineers . They support sending Ethernet frames at 40 and 100 gigabits per second over multiple 10 Gbit/s or 25 Gbit/s lanes...
were standardized in 2010 and 2011.
Ethernet's dominance is partly attributed to the simple advantages for the industry of adopting a single standard to drive up volumes and drive down prices. In part, it is also due to ease of deployment, using its ability to self-configure itself based on the key concepts of “learning bridge”, (flooding, and associating learned destination addresses
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...
with bridge ports) and "spanning tree protocol
Spanning tree protocol
The Spanning Tree Protocol is a network protocol that ensures a loop-free topology for any bridged Ethernet local area network. The basic function of STP is to prevent bridge loops and ensuing broadcast radiation...
," (the protocol used for avoiding bridging loops).
Historically, competing protocols and cabling have been created in order to access higher speed devices than contemporary Ethernet-connected devices handled at an affordable price. Examples include FireWire and Light Peak
Light Peak
Thunderbolt is an interface for connecting peripheral devices to a computer via an expansion bus. Thunderbolt was developed by Intel and brought to market with technical collaboration from Apple Inc. It was introduced commercially on Apple's updated MacBook Pro lineup on February 24, 2011, using...
. One motive to create competing standards has been to drive down the price of comparable-speed Ethernet devices. Once this purpose is achieved, competing standards tend to disappear or be confined to very specialized niches.
Ethernet is a fairly simple protocol which has scaled to hundreds of thousands of times faster speeds and consistently been able to adapt to meet the needs and demands of new markets. For example, time domain capabilities are being added to IEEE 802.3 Ethernet to support IEEE 802.1 audio/video bridging (AVB) , and these capabilities will be applicable to time sensitive carrier applications likewise IEEE 1588.
Customer LAN networks are increasingly connected to wide-area telecommunications networks over Ethernet interfaces or to devices that bridge DSL or wireless to these. Moreover, customers are familiar with the capabilities of Ethernet networks, and would like to extend these capabilities to multi-site networks. Meanwhile the needs of such networks have expanded to include many services previously handled only on the LAN or by specialized connections, notably video and backup. It is not practical to expand most small networks beyond 1G or at most 2G (dual teaming gigabit) capacity per segment, since the bottleneck remains in the wide area links to other offices and online services.
Carrier constraints
Thus wide area networkWide area network
A wide area network is a telecommunication network that covers a broad area . Business and government entities utilize WANs to relay data among employees, clients, buyers, and suppliers from various geographical locations...
(WAN) and metropolitan area network
Metropolitan area network
A metropolitan area network is a computer network that usually spans a city or a large campus. A MAN usually interconnects a number of local area networks using a high-capacity backbone technology, such as fiber-optical links, and provides up-link services to wide area networks and the...
(MAN) providers find themselves with three needs:
- To provide their customers with Ethernet services
- To make use of the volume and cost advantages of Ethernet technologies in their networks
- To replace non-Ethernet technologies with Ethernet competitors that have sufficient capacity for storage, backup and HD video and guarantee features (transfer certainty, low latency) needed to support these services
They are also constrained as services cannot be migrated from local to wide area services too fast lest they exceed the total provisioning available and result in unacceptable quality. Services that try to expand too fast lose money while those that wait too long lose customers. Accordingly carriers must expand their services conservatively and pay close attention to 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...
(QoS).
The Beginning: Metro Ethernet
The MEF was formed in 2001 in order to develop ubiquitous business services for Enterprise users principally accessed over optical metropolitan networks in order to connect their Enterprise LANs. The principal concept was to bring the simplicity and cost model of Ethernet to the wide area network.Expansion to Carrier Ethernet
The success of Metro Ethernet Services caught the imagination of the world when the concept expanded to include worldwide services traversing national and global networks:- Access networks to provide availability to a much wider class of user over fiber, copper, cable, PON, and wireless
- Economy of scale from the resulting converged business, residential and wireless networks sharing the same infrastructure and services
- Scalability & rapid deployment of business applications
- Adoption of the certification program
- All while retaining the cost model and simplicity of Ethernet
Carrier Ethernet services
To create a market in Ethernet services, it is necessary to clarify and standardise the services to be provided. Recognising this, the industry created the Metro Ethernet ForumMetro Ethernet Forum
The Metro Ethernet Forum , founded in 2001, is a nonprofit international industry consortium, dedicated to worldwide adoption of Carrier Ethernet networks and services....
http://www.metroethernetforum.org. This played a key role in defining:
- E-line: a service connecting two customer Ethernet ports over a WAN. Not to be confused with E-line from Corridor which is a proprietary protocol for outdoor powerline networking under 1km range and competes with Ethernet services.
- E-LAN: a multipoint service connecting a set of customer endpoints, giving the appearance to the customer of a bridged Ethernet network connecting the sites.
- E-tree: a multipoint service connecting one or more roots and a set of leaves, but preventing inter-leaf communication.
All these services provide standard definitions of such characteristics as bandwidth, resilience and service multiplexing, allowing customers to compare service offerings and facilitating service level agreement
Service Level Agreement
A service-level agreement is a part of a service contract where the level of service is formally defined. In practice, the term SLA is sometimes used to refer to the contracted delivery time or performance...
s (SLAs). Analogous definitions for wireless networks are defined in IEEE 802.21
IEEE 802.21
802.21 is an IEEE standard published in 2008. The standard supports algorithms enabling seamless handover between networks of the same type as well as handover between different network types also called Media independent handover or vertical handover...
and IEEE 802.11u
IEEE 802.11u
IEEE 802.11u-2011 is an amendment to the IEEE 802.11-2007 standard to add features that improve interworking with external networks.802.11 is a family of IEEE technical standards for mobile communication devices such as laptop computers or multi-mode phones to join a wireless local area network ...
, though these are intended for much shorter time commitments and services appropriate for mobile users only.
Transport of Ethernet services
The Metro Ethernet ForumMetro Ethernet Forum
The Metro Ethernet Forum , founded in 2001, is a nonprofit international industry consortium, dedicated to worldwide adoption of Carrier Ethernet networks and services....
does not specify how Ethernet services are to be provided in a carrier network. Despite the advantages described above, Ethernet has traditionally had a number of limitations in the WAN application. The "bridge" and "spanning tree" concepts described above do not scale to large international networks. Moreover, Ethernet has lacked some of the dependability features necessary in this application (in particular, mechanisms to isolate one customer's traffic from another, to measure performance of a customer service instance, and to rapidly detect and repair failures in large networks).
Because of these limitations, and because of the need to make use of pre-existing equipment, Ethernet services have been carried across wide area networks using other technologies. Two types of technology have been widely used, while a third (Carrier-Ethernet transport) is rapidly emerging as a viable and logical option for Carrier-Ethernet services.
Ethernet over SDH/SONET
Point-to-point Ethernet links are carried over SDH/SONETSynchronous optical networking
Synchronous Optical Networking and Synchronous Digital Hierarchy are standardized multiplexing protocols that transfer multiple digital bit streams over optical fiber using lasers or highly coherent light from light-emitting diodes . At low transmission rates data can also be transferred via an...
networks, making use of virtual concatenation (ITU-T G.707) and LCAS (Link Capacity Adjustment Scheme - ITU-T G.7042) to create an appropriate size carrier bundle, and of Generic Framebase of SDH equipment, and takes advantage of the management and recovery features of SDH to provide high availability
High availability
High availability is a system design approach and associated service implementation that ensures a prearranged level of operational performance will be met during a contractual measurement period....
and resilience to failures.
Ethernet over MPLS
Ethernet services are carried over IPInternet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
/MPLS
Multiprotocol Label Switching
Multiprotocol Label Switching is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links between...
networks making use of a wide range of IP-related protocols
Internet protocol suite
The Internet protocol suite is the set of communications protocols used for the Internet and other similar networks. It is commonly known as TCP/IP from its most important protocols: Transmission Control Protocol and Internet Protocol , which were the first networking protocols defined in this...
(see IETF pseudowire standards, e.g. RFC 3985, RFC 4448). Ethernet links are transported as “pseudowires” using MPLS
Mpls
MPLS or Mpls can refer to:* Minneapolis, Minnesota, United States* Multiprotocol Label Switching, a data-carrying mechanism in computer networking...
label switched path
Label Switched Path
In MPLS networking, a Label Switched Path is a path through an MPLS network, set up by a signaling protocol such as LDP, RSVP-TE, BGP or CR-LDP. The path is set up based on criteria in the forwarding equivalence class ....
s (LSPs) inside an outer MPLS “tunnel”. This strategy can support both point-to-point (Virtual Private Wire Service - VPWS) and multipoint (Virtual Private LAN service - VPLS) services, and has recently achieved significant deployment in routed networks. It makes use of a number of basic transport protocols, including SDH and (increasingly) Ethernet.
Ethernet over Carrier-Ethernet Transport (CET)
Proponents of Carrier-Class Ethernet argue that, since all data traffic originates as Ethernet, no other technology could be better than Ethernet itself to carry this traffic in Metro Area Networks. Ethernet’s ubiquitous presence in the LANs worldwide drives down the cost of Ethernet as a technology. Thus, the use of Ethernet in a metro network allows service providers to take advantage of volumes that a much-larger enterprise segment commands. Carrier-Ethernet Transport (CET) usually involves an evolution of conventional Ethernet and comprises multiple technology components. Provider Backbone Bridges (PBB) provides the scalability and a secure demarcation, while PBB-TE (commonly called PBT) provides for traffic-engineering and an effective transport for protected Ethernet services. Connectivity-Fault Management (CFM-OAM) provides the much-required OAM that makes Ethernet carrier gradeCarrier grade
In telecommunication, a "carrier grade" or "carrier class" refers to a system, or a hardware or software component that is extremely reliable, well tested and proven in its capabilities...
.
Carrier Ethernet Demarcation
Carrier Ethernet demarcation is a key element in Carrier Ethernet services and transport networks for business, wholesale and mobile backhaul applications, as it enables service providers to extend their control over the entire service path, starting from the hand off points. This is achieved by connecting customer premises equipment (CPE) to the network with provider-owned demarcation devices that are deployed at customer locations, thereby enabling a clear separation between the user and provider networks.Carrier Ethernet demarcation devices are required to support services, such as EPL (Ethernet Private Line), EVPL (Ethernet Virtual Private Line), E-LAN (Ethernet LAN), and E-Tree (Ethernet Tree), as specified by the MEF (Metro Ethernet Forum). Such support needs to include SLA (service level agreement) management capabilities, with consistent performance over fiber, DSL, bonded PDH, and SDH/SONET access lines. As a result, must-have Carrier Ethernet demarcation features include sophisticated traffic management and hierarchical QoS (quality of service) mechanisms, standard end-to-end OAM (operations, administration and maintenance) and performance monitoring, extensive fault management and diagnostics, and SDH/SONET-like resiliency to reduce service provider operating costs and capital expenses.
Carrier Ethernet technologies
The industry has made a concerted effort to resolve the limitations of Ethernet in the WAN described above, so as to allow the use of "native" Ethernet technologies by network providers.The key roles have been played by the Institute of Electrical and Electronic Engineers (IEEE) 802.1 and 802.3 standards committees. IEEE 802.1 has addressed the scalability and management issues in the standards for Provider Bridges (802.1ad) and Provider Backbone Bridges (802.1ah). These standards allow for Ethernet networks of planetary scale. Associated standards (IEEE 802.1ag, and related ITU-T standard Y.1731) provide Operations and Maintenance (OAM) capabilities allowing connectivity verification, rapid recovery, and performance measurement. Current work on PBB-TE (802.1Qay: Provider Backbone Bridging-Traffic Engineering) is allowing such an Ethernet to be controlled by an external control or management application (for example, a network management application or a transport control plane such as GMPLS (IETF RFC 3945)), so as to allow the full range of traffic engineering policies and strategies to a network provider.
The IEEE 802.3 Working Group in close cooperation with the ITU
Itu
Itu is an old and historic municipality in the state of São Paulo in Brazil. The population in 2009 was 157,384 and the area is 641.68 km². The elevation is 583 m. This place name comes from the Tupi language, meaning big waterfall. Itu is linked with the highway numbered the SP-75 and are flowed...
have been working to simplify the transport of 40G and 100G technologies being developed by both bodies: 802.3 for LAN and ITU for the OTN
Optical Transport Network
ITU-T defines an Optical Transport Network as a set of Optical Network Elements connected by optical fibre links, able to provide functionality of transport, multiplexing, switching, management, supervision and survivability of optical channels carrying client signals...
. The OIF
Optical Internetworking Forum
The Optical Internetworking Forum is a non-profit, member-driven organization founded in 1998. It promotes the development and deployment of interoperable networking solutions and services through the creation of Implementation Agreements for optical networking products, network processing...
and the Ethernet Alliance
Ethernet Alliance
The Ethernet Alliance was incorporated in the state of California in August 2005 and officially launched in January 2006 as a global non-profit industry consortium to promote and support Ethernet...
have also been working cooperatively with their members to enable future enhancements to Ethernet for the WAN while looking to the future speed of Ethernet technologies and services.
See also
- Ethernet in the First MileEthernet in the First MileEthernet in the first mile refers to using one of the Ethernet family of computer network protocols between a telecommunications company and a customer's premise. From the customer's point of view it is their "first" mile, although from the access networks' point of view it is known as the "last...
(EFM) - 10PASS-TS10PASS-TS10PASS-TS is an IEEE 802.3-2008 Physical Layer specification for a full-duplex short reach point-to-point Ethernet link over voice-grade copper wiring, used in Ethernet in the first mile applications....
(Ethernet over VDSL) - Metro EthernetMetro EthernetA Metro Ethernet is a computer network that covers a metropolitan area and that is based on the Ethernet standard. It is commonly used as a metropolitan access network to connect subscribers and businesses to a larger service network or the Internet...
- Provider Backbone Bridges
- Provider Backbone Bridge Traffic EngineeringProvider Backbone Bridge Traffic EngineeringProvider Backbone Bridge Traffic Engineering is an approved telecommunications networking standard, IEEE 802.1Qay-2009. PBB-TE adapts Ethernet technology to carrier class transport networks...
- Connection-oriented EthernetConnection-oriented EthernetConnection-oriented Ethernet refers to the transformation of Ethernet, a connectionless communication system by design, into a connection-oriented system. The aim of connection-oriented Ethernet is to create a networking technology that combines the flexibility and cost-efficiency of Ethernet with...
- IEEE 802.1ad VLAN stacking or Q-in-Q
- IEEE 802.1AX Link Aggregation
- IEEE 802.1aqIEEE 802.1aq802.1aq Shortest Path Bridging or SPB in computer networking is a technology that greatly simplifies the creation and configuration of carrier, enterprise, and cloud networks which virtually eliminates human error, while enabling multipath routing...
Shortest Path Bridging - IEEE 802.1ah-2008 Provider Backbone Bridges
External Links
- http://metroethernetforum.org/CarrierEthernetinActionOverview - Metro Ethernet Forum, overview of Carrier Ethernet