Carrier Ethernet

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Carrier Ethernet is a marketing term for extensions to Ethernet for communications service providers that utilize Ethernet technology in their networks.

Contents

Background

Ethernet 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 rates 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. [1] [2] [3]

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 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), [4] 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 digital subscriber line (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 network (WAN) and metropolitan area network (MAN) providers find themselves with three needs:

  1. To provide their customers with Ethernet services
  2. To make use of the volume and cost advantages of Ethernet technologies in their networks
  3. 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 (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. [5]

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: [5]

  • Access networks to provide availability to a much wider class of user over fiber, copper, cable, passive optical network (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 MEF. 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 agreements (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.

Ethernet Virtual Private Tree

Ethernet Virtual Private Tree or E-Tree is a point-to-multipoint Ethernet Virtual Connection defined by the MEF — an Ethernet VLAN configuration suitable for multicast services.

Ethernet private line

Ethernet private line (EPL) and Ethernet virtual private line (EVPL) are data services defined by the MEF. EPL provides a point-to-point Ethernet virtual connection (EVC) between a pair of dedicated user–network interfaces (UNIs), with a high degree of transparency. EVPL provides a point-to-point or point-to-multipoint connection between a pair of UNIs.

The services are categorized as an E-line service type, with an expectation of low frame delay, frame delay variation and frame loss ratio. EPL is implemented using a point-to-point EVC with no service multiplexing at each UNI (physical interface), i.e., all service frames at the UNI are mapped to a single EVC (a.k.a. all-to-one bundling).

Due to a high degree of transparency, EPL is often used to provide point-to-point transparent LAN service (TLS), where the service frame's header and payload are identical at both the source and destination UNI. Some implementations tunnel most Ethernet Layer 2 control protocols (L2CPs) except for some link-layer L2CPs such as IEEE 802.3x pause frames.

Unlike EPL, EVPL allows for service multiplexing, i.e., multiple EVCs or Ethernet services per UNI. The other difference between the EVPL and EPL is the degree of transparency: while EPL is highly transparent, filtering only the pause frames, EVPL is required to either peer or drop most of the Layer 2 control protocols.

Ethernet Virtual Private LAN

Ethernet Virtual Private LAN (EVP-LAN) is a multipoint-to-multipoint Ethernet Virtual Connection defined by the MEF — a Carrier Ethernet equivalent of Virtual Private LAN Service (VPLS) or Transparent LAN Services. EVP-LAN enables any-to-any communication between all customer locations associated with the customer's Ethernet Virtual Connections (EVC). It is categorized as an E-LAN service type, with an expectation of low Frame Delay, Frame Delay Variation and Frame Loss Ratio. Service multiplexing is allowed at the UNI and EVPL and EVP-LAN service types may share the same port. CE-VLAN IDs are maintained across the network.

Transport of Ethernet services

The MEF 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).[ citation needed ] 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/SONET 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, of the Generic Framing Procedure of SDH equipment, and takes advantage of the management and recovery features of SDH to provide high availability and resilience to failures.

Ethernet over MPLS

Ethernet services are carried over IP/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 paths (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 Ethernet is the best for Metro Area Networks because all data traffic originates as Ethernet. 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 Provider Backbone Bridge Traffic Engineering (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 grade.

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 (EDD) are required to support services, such as Ethernet Private Line (EPL), Ethernet Virtual Private Line (EVPL or E-LAN), and Ethernet Virtual Private Tree (E-Tree), as specified by the MEF. Such support needs to include service level agreement (SLA) 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 quality of service (QoS) mechanisms, standard end-to-end operations, administration and maintenance (OAM) and performance monitoring, extensive fault management and diagnostics, and SDH/SONET-like resiliency to reduce service provider operating costs and capital expenses. [6]

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.[ citation needed ] The key roles have been played by the Institute of Electrical and Electronics 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.[ citation needed ] 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.[ citation needed ]

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.

See also

Related Research Articles

<span class="mw-page-title-main">Metropolitan area network</span> Computer network serving a populated area

A metropolitan area network (MAN) is a computer network that interconnects users with computer resources in a geographic region of the size of a metropolitan area. The term MAN is applied to the interconnection of local area networks (LANs) in a city into a single larger network which may then also offer efficient connection to a wide area network. The term is also used to describe the interconnection of several LANs in a metropolitan area through the use of point-to-point connections between them.

In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer: the layer most closely associated with the physical connection between devices. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to transmit on, the line code to use and similar low-level parameters, are specified by the physical layer.

A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer. In this context, virtual refers to a physical object recreated and altered by additional logic, within the local area network. VLANs work by applying tags to network frames and handling these tags in networking systems – creating the appearance and functionality of network traffic that is physically on a single network but acts as if it is split between separate networks. In this way, VLANs can keep network applications separate despite being connected to the same physical network, and without requiring multiple sets of cabling and networking devices to be deployed.

A virtual private network (VPN) is a mechanism for creating a secure connection between a computing device and a computer network, or between two networks, using an insecure communication medium such as the public Internet.

Virtual Private LAN Service (VPLS) is a way to provide Ethernet-based multipoint to multipoint communication over IP or MPLS networks. It allows geographically dispersed sites to share an Ethernet broadcast domain by connecting sites through pseudowires. The term sites includes multiplicities of both servers and clients. The technologies that can be used as pseudo-wire can be Ethernet over MPLS, L2TPv3 or even GRE. There are two IETF standards-track RFCs describing VPLS establishment.

<span class="mw-page-title-main">Metro Ethernet</span> Metropolitan area network based on Ethernet standards

A metropolitan-area Ethernet, Ethernet MAN, carrier Ethernet or metro Ethernet network is a metropolitan area network (MAN) that is based on Ethernet standards. It is commonly used to connect subscribers to a larger service network or for internet access. Businesses can also use metropolitan-area Ethernet to connect their own offices to each other.

IEEE 802.1ag is an amendment to the IEEE 802.1Q networking standard which introduces Connectivity Fault Management (CFM). This defines protocols and practices for the operations, administration, and maintenance (OAM) of paths through 802.1 bridges and local area networks (LANs). The final version was approved by the IEEE in 2007.

<span class="mw-page-title-main">Computer network</span> Network that allows computers to share resources and communicate with each other

A computer network is a set of computers sharing resources located on or provided by network nodes. Computers use common communication protocols over digital interconnections to communicate with each other. These interconnections are made up of telecommunication network technologies based on physically wired, optical, and wireless radio-frequency methods that may be arranged in a variety of network topologies.

In a hierarchical telecommunications network, the backhaul portion of the network comprises the intermediate links between the core network, or backbone network, and the small subnetworks at the edge of the network.

Provider Backbone Bridge Traffic Engineering (PBB-TE) is a computer networking technology specified in IEEE 802.1Qay, an amendment to the IEEE 802.1Q standard. PBB-TE adapts Ethernet to carrier class transport networks. It is based on the layered VLAN tags and MAC-in-MAC encapsulation defined in IEEE 802.1ah, but it differs from PBB in eliminating flooding, dynamically created forwarding tables, and spanning tree protocols. Compared to PBB and its predecessors, PBB-TE behaves more predictably and its behavior can be more easily controlled by the network operator, at the expense of requiring up-front connection configuration at each bridge along a forwarding path. PBB-TE Operations, Administration, and Management (OAM) is usually based on IEEE 802.1ag. It was initially based on Nortel's Provider Backbone Transport (PBT).

IEEE 802.1ah is an amendment to the IEEE 802.1Q networking standard which adds support for Provider Backbone Bridges. It includes an architecture and a set of protocols for routing over a provider's network, allowing interconnection of multiple provider bridge networks without losing each customer's individually defined VLANs. It was initially created by Nortel before being submitted to the IEEE 802.1 committee for standardization. The final version was approved by the IEEE in June 2008 and has been integrated into IEEE 802.1Q-2011.

MEF, founded in 2001, is a nonprofit international industry consortium, of network, cloud, and technology providers. MEF, originally known as the Metro Ethernet Forum, was dedicated to Carrier Ethernet networks and services, and in recent years, significantly broadened its scope, which now includes underlay connectivity services such as Optical, Carrier Ethernet, IP, along with overlay digital services including SD-WAN Services, as well as APIs to support orchestration of the service lifecycle. Along with this change in scope, MEF re-branded from the "Metro Ethernet Forum", to simply "MEF". "MEF Forum" is MEF's legal name.

Connection-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 the reliability of connection-oriented protocols. Connection-oriented Ethernet is used in commercial carrier grade networks.

Hierarchical VLAN (HVLAN) is a proposed Ethernet standard that extends the use of enterprise Ethernet VLAN (802.1Q) to carrier networks. A number of developments have emerged in recent years to help bring Ethernet, a flexible and cost-efficient packet transport technology, to carrier networks. These developments include Q-in-Q (802.1ad), PBB (802.1ah), PBT, and PBB-TE, which bring a set of features to traditional Ethernet to make it “carrier-grade”, adding to it high-availability, OA&M, and more.

Data center bridging (DCB) is a set of enhancements to the Ethernet local area network communication protocol for use in data center environments, in particular for use with clustering and storage area networks.

IEEE 802.1aq is an amendment to the IEEE 802.1Q networking standard which adds support for Shortest Path Bridging (SPB). This technology is intended to simplify the creation and configuration of Ethernet networks while enabling multipath routing.

IEEE 802.1ad is an amendment to the IEEE 802.1Q-1998 networking standard which adds support for provider bridges. It was incorporated into the base 802.1Q standard in 2011. The technique specified by the standard is known informally as stacked VLANs or QinQ.

ITU-T Y.156sam Ethernet Service Activation Test Methodology is a draft recommendation under study by the ITU-T describing a new testing methodology adapted to the multiservice reality of packet-based networks.

Time-Sensitive Networking (TSN) is a set of standards under development by the Time-Sensitive Networking task group of the IEEE 802.1 working group. The TSN task group was formed in November 2012 by renaming the existing Audio Video Bridging Task Group and continuing its work. The name changed as a result of the extension of the working area of the standardization group. The standards define mechanisms for the time-sensitive transmission of data over deterministic Ethernet networks.

An Ethernet virtual connection or Ethernet virtual circuit (EVC) defines a data link layer bridging architecture that supports Ethernet services. An EVC is defined by the Metro-Ethernet Forum (MEF) as an association between two or more user network interfaces that identifies a point-to-point or multipoint-to-multipoint path within the service provider network. An EVC is a conceptual service pipe within the service provider network. A bridge domain is a local broadcast domain that exists separately from VLANs.

References

  1. ↑ "IEEE P802.3ba 40Gb/s and 100Gb/s Ethernet Task Force". official web site. IEEE 802. June 19, 2010. Retrieved August 6, 2011.
  2. ↑ IEEE P802.3ba 40 Gb/s and 100 Gb/s Ethernet Task Force : http://ieee802.org/3/ba/
  3. ↑ IEEE P802.3bg 40G SMF PMD for Carrier Client Task Force : http://www.ieee802.org/3/40GSMF/
  4. ↑ IEEE 802.1 Audio/Video Bridging
  5. 1 2 "Carrier Ethernet and CE 2.0". MEF. Archived from the original on 23 September 2015. Retrieved 22 September 2015.
  6. ↑ "Carrier Ethernet & CE 2.0". Archived from the original on 2015-09-23.
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