Connection-oriented Ethernet

Last updated

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.

Contents

Traditional carrier networks deliver services at very high availability. Packet-switched networks are different, as they offer services based on statistical multiplexing. Moreover, packet transport equipment, which makes up the machinery of data networking, leaves most of the carrier-grade qualities such as quality of service, routing, provisioning, and security, to be realized by packet processing. Addressing these needs in a cost-efficient way is a challenge for packet-based technologies.

The IP-MPLS approach aims at providing guaranteed services over the Internet Protocol using a multitude of networking protocols to create, maintain and handle packet data streams. While this approach solves the problem, it inevitably also creates a great deal of complexity.

This has resulted in the emergence of connection-oriented Ethernet which includes a variety of methodologies to utilize Ethernet for the same functionalities otherwise based on extensive IP protocols. The challenge of carrier Ethernet is to add carrier-grade functionality to Ethernet equipment without losing the cost-effectiveness and simplicity that makes it attractive in the first place. To meet this challenge, common connection-oriented Ethernet solutions have chosen to rid themselves of the complex parts of packet transport to achieve stability and control. Key connection-oriented Ethernet technologies used to achieve this include mainly IEEE 802.1ah, Provider Backbone Transport and MPLS-TP, and formerly T-MPLS.

PBT and PBB

Provider Backbone Transport (PBT) is connection-oriented switch operation scheme and network management architecture. PBT was invented by British Telecom (BT) and developed by Nortel (now Avaya). It defines methods to emulate connection-oriented networks by providing "nailed-up" trunks through a packet-switched network. Key data-plane differences from PBB include the static configuration of forwarding tables within Ethernet switches, dropping of multicast packets and the prevention of "flooding" of frames to unknown destination addresses. Configuration is performed by a centralized management server like in SDH networks, though in the future a control plane may be added. PBT has been presented to IEEE802 and a new project has been approved to standardize it under the name of Provider Backbone Bridge Traffic Engineering (PBB-TE) (IEEE 802.1Qay), a modification to PBB.

Provider Backbone Bridges (PBB) is an Ethernet data-plane technology invented in 2004 by Nortel Networks (now Avaya). It is sometimes known as MAC-in-MAC because it involves encapsulating an Ethernet datagram inside another one with new source and destination addresses (termed B-SA and B-DA). IEEE802 is standardizing the technology as (IEEE 802.1ah), currently under development. PBB is the original data-plane chosen by British Telecom for their new PBT-based Ethernet transport.

PBB can support point-to-point, point-to-multipoint and multipoint-to-multipoint networks. PBT focuses on point-to-point connectivity, and may be capable of extension to point-to-multipoint, a key technology for advanced data applications such as IPTV. PBT avoids trying to address multipoint-to-multipoint networking, as in the opinion of some of its supporters guaranteed levels of service in multipoint-to-multipoint networks are impossible.

Additionally Ethernet is being reinforced with operations, administration, and maintenance (OAM) capabilities through the work of various standard bodies (IEEE 802.1ag, ITU-T Y.1731 and G.8021, IEEE 802.3ah).

PBT/PBB equipment leverages economies of scale inherent in Ethernet, promising about 30%–40% cheaper solutions compared to T-MPLS equipment with identical features and capabilities, [1] making PBT a better overall return on investment. [2]

T-MPLS (Transport MPLS) / MPLS-TP (MPLS Transport Profile)

T-MPLS, as its name implies, is a derivative of MPLS that renounces all MPLS signaling features and, like PBT, uses a centralized control-plane to perform routing and traffic engineering. T-MPLS is currently being standardized only at ITU-T and enjoys strong vendor support but little carrier support.

As a native MPLS derivative, T-MPLS can be easily implemented over existing MPLS routers. However, T-MPLS has been stripped of the characteristics which originally made it attractive to carriers—control-plane automation, signaling, and QoS—and therefore has yet to prove its benefits for the transport network. T-MPLS OAM, defined in ITU Y.1711, is different from MPLS OAM and lacks powerful management tools that carriers typically expect. T MPLS was abandoned by the ITU-T in favor of MPLS-TP in December 2008. [3]

MPLS-TP or MPLS Transport Profile is a profile of MPLS developed in cooperation between ITU-T and IETF since 2008 as a connection-oriented packet-switched (CO-PS) extension. Based on the same architectural principles of layered networking that are used in longstanding transport network technologies like SDH, SONET, and OTN, MPLS-TP provides a reliable packet-based L2 technology that is comparable to circuit-based transport networking, and thus aligned with current organizational processes and large-scale work procedures similar to other packet transport technologies.

Achieving the promise of carrier-grade Ethernet

Services in the data network are typically classified into 2 major categories: Committed Information Rate (CIR) and Excess Information Rate (EIR). A CIR service guarantees its user a fixed amount of bandwidth, whereas an EIR service offers best-effort only transport. Both types of services share a single capacity-constrained infrastructure. Both are further defined by additional parameters.

A carrier's return on investment is directly related to its ability to transport more service instances over a fixed capacity-constrained infrastructure, keeping Quality of Service high. It is further associated with its ability to offer a broad range of added-value services, such as IPTV, Voice, and VPN, whose requirements can widely vary and pose technical difficulties when sharing the same infrastructure.

With the above in mind, the carrier's objective is to offer a maximum amount of best-effort EIR services over its network while reliably serving its committed CIR services. To achieve this PBB/PBT and T-MPLS approaches largely under-provision network resources, in order to avoid a situation where a burst in best-effort traffic would jeopardize the ability to serve committed traffic, leading to costly penalties. An additional issue with best-effort access on data networks is fair allocation among clients. With PBB/PBT and T-MPLS, the amount of bandwidth available to a particular client greatly depends on the client's location and the prevailing traffic conditions. This limits the value customers attach to EIR services and undercuts carriers' opportunities to offer differentiated access to its excess capacity.

Performing traffic engineering in real-time is thus key to next-generation Ethernet transport. Additional qualities are required to make Ethernet a carrier-grade technology:

Multi-vendor support, the ability to support a variety of Ethernet switches in the core, is a desirable attribute as it allows carriers to use inexpensive switches to build their metro transport network. Vendors such as Tejas Networks, Ethos Networks, and Nortel offer solutions which meet the above requirements, yet preserve Ethernet's simplicity and flexibility.

See also

Related Research Articles

Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses. Whereas network addresses identify endpoints the labels identify established paths between endpoints. MPLS can encapsulate packets of various network protocols, hence the multiprotocol component of the name. MPLS supports a range of access technologies, including T1/E1, ATM, Frame Relay, and DSL.

<span class="mw-page-title-main">Frame Relay</span> Wide area network technology

Frame Relay is a standardized wide area network (WAN) technology that specifies the physical and data link layers of digital telecommunications channels using a packet switching methodology. Originally designed for transport across Integrated Services Digital Network (ISDN) infrastructure, it may be used today in the context of many other network interfaces.

In the IEEE 802 reference model of computer networking, the logical link control (LLC) data communication protocol layer is the upper sublayer of the data link layer of the seven-layer OSI model. The LLC sublayer acts as an interface between the media access control (MAC) sublayer and the network layer.

A virtual private network (VPN) extends a private network across a public network and enables users to send and receive data across shared or public networks as if their computing devices were directly connected to the private network. The benefits of a VPN include increases in functionality, security, and management of the private network. It provides access to resources that are inaccessible on the public network and is typically used for remote workers. Encryption is common, although not an inherent part of a VPN connection.

Resilient Packet Ring (RPR), as defined by IEEE standard 802.17, is a protocol designed for the transport of data traffic over optical fiber ring networks. The standard began development in November 2000 and has undergone several amendments since its initial standard was completed in June 2004. The amended standards are 802.17a through 802.17d, the last of which was adopted in May 2011. It is designed to provide the resilience found in SONET and Synchronous Digital Hierarchy networks but, instead of setting up circuit oriented connections, provides a packet based transmission, in order to increase the efficiency of Ethernet and IP services.

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.

The next-generation network (NGN) is a body of key architectural changes in telecommunication core and access networks. The general idea behind the NGN is that one network transports all information and services by encapsulating these into IP packets, similar to those used on the Internet. NGNs are commonly built around the Internet Protocol, and therefore the term all IP is also sometimes used to describe the transformation of formerly telephone-centric networks toward NGN.

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

A metropolitan-area Ethernet, Ethernet MAN, 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 the Internet. Businesses can also use metropolitan-area Ethernet to connect their own offices to each other.

<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. The 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.

Ethernet in the first mile (EFM) refers to using one of the Ethernet family of computer network technologies between a telecommunications company and a customer's premises. From the customer's point of view, it is their first mile, although from the access network's point of view it is known as the last mile.

Operations, administration and management or operations, administration and maintenance are the processes, activities, tools, and standards involved with operating, administering, managing and maintaining any system. This commonly applies to telecommunication, computer networks, and computer hardware.

Provider Backbone Bridge Traffic Engineering (PBB-TE) is an approved telecommunications networking standard, IEEE 802.1Qay-2009. PBB-TE adapts Ethernet technology 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).

Provider Backbone Bridges is a set of architecture and 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 standard was approved by the IEEE in June 2008 as IEEE 802.1ah-2008 and has been integrated into IEEE 802.1Q-2011.

T-MPLS or Transport MPLS is a transport network layer technology that uses extensions to a subset of the existing MPLS standards and is designed specifically for application in transport networks. Work to define T-MPLS was started by the ITU-T in February 2006. It was intended specifically as a connection-oriented packet-switched (co-ps) application offering a simpler implementation by removing MPLS features that are not relevant to co-ps applications and adding mechanisms that provide support of critical transport functionality.

<span class="mw-page-title-main">Metro Ethernet Routing Switch 8600</span>

Metro Ethernet Routing Switch 8600 or MERS 8600 is a modular chassis router and/or switch manufactured by Nortel now acquired by Ciena. The MERS 8600 supports the Provider Backbone Bridges (PBB), Provider Backbone Transport (PBT) technologies and carrier class Operations Administration & Maintenance (OAM) tools.

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.

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

In telecommunications, Multiprotocol Label Switching - Transport Profile (MPLS-TP) is a variant of the MPLS protocol that is used in packet switched data networks. MPLS-TP is the product of a joint Internet Engineering Task Force (IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network.

Shortest Path Bridging (SPB), specified in the IEEE 802.1aq standard, is a computer networking technology intended to simplify the creation and configuration of networks, while enabling multipath routing.

References

This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.