Pseudowire and Circuit Emulation Services Overview
Pseudowires enable you to carry legacy Layer 2 services over a cost-effective and predominant deployed underlying network. It decouples the services protocol and applications from the underlying facilities that carry them.
The underlying physical network could be intellectual property (IP)/multiprotocol label switching (MPLS), Ethernet, WiMAX, P2P Microwave, DOCSIS, or PON, depending on the application (see Figure 1). Pseudowires evolved as the technology that enables you to build fully converged networks as a result of the general move towards IP/MPLS-based networks. You can carry traffic from any one physical layer to another, while still enjoying the benefits by deploying a converged solution that significantly reduces the capital expenses and operating expenditures. Circuit emulation services (CES) is a class of pseudowire that allows service providers to carry traditional time-domain multiplexing (TDM) services (such as voice) over a packet network that is deployed using Ethernet running over copper or other cost-effective, predominant network.
Pseudowire emulation edge to edge (PWE3) defines a way to transport the native transport over a packet switched network (PSN) by encapsulating the traditional transport cells into IP packets. On the receive side, the packets are de-capsulated and converted into native transport cell-streams, while "emulating” the service parameters governing the original transport service.
Though this technology started out as an IETF standard based on IP/MPLS to carry legacy transport services such as asynchronous transfer mode (ATM), frame relay, or Ethernet over a PSN, it is now proliferating end to end across the various network segments. CES originated later to use pseudowire principles to carry voice/TDM services for access and metro networks.
Figure 1. Flexible Inter-Working Through Pseudowire
Altera and its ecosystem partners provide solutions for all three of the following PWE3 implementation steps:
- Data path processing
- Control functions
- Operation administration and maintenance (OAM) functions
Metro and Edge Network
PWE3 allows you to deploy SONET such as metro rings using Ethernet as the underlying layer. This layer allows you to deploy revenue-bearing E-LINE and E-LAN services while still maintaining redundancy of links and guarantees fail-over loop times by complying with Metro Ethernet Forum (MEF) guidelines.
Access Network
As access networks migrate from ATM to IP, backhaul pseudowire and circuit emulation technology support that transition by allowing you to use cheaper Ethernet over copper lines while still providing the existing service level agreements to the end customer. CES also allows you to maintain a single converged network (instead of two) for backhauling traffic for both wireline or wireless access networks, hence reducing the total capital expenditure and delivering new revenue generating services such as fixed mobile convergence.
First Mile
In the first mile and near the customers premise equipment, CES allows you to carry services over existing Layer 2 technologies. This allows for billing on a packet basis (better metered revenue) while carrying data, voice, and video over any physical medium. Popular Layer 2 technologies include xPON (for fiber), xDSL (copper), and DOCSIS (coaxial). Service providers are looking at solutions for flexible backhaul techniques to backhaul traffic from femtocell base stations, optical network node (ONT), residential gateways and set-top boxes back to the central office. These include CESoGPON, CESoDOCSIS, and synchronization techniques.
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