Pseudowires (PWs) manage encapsulation, timing, order, and other operations in order to make it transparent to users; the PW tunnel appears as an unshared link or circuit of the emulated service.
There are limitations that impede some applications from utilizing a PW connection.
Cisco supports the following standards-based PWE types:
Structure-Agnostic TDM over Packet
SAToP encapsulates TDM bit-streams (T1, E1, T3, E3) as PWs over PSNs. It disregards any structure that may be imposed on streams, in particular the structure imposed by the standard TDM framing. The protocol used for emulation of these services does not depend on the method in which attachment circuits are delivered to the PEs. For example, a T1 attachment circuit is treated the same way for all delivery methods, including: PE on copper, multiplex in a T3 circuit, mapped into a virtual tributary of a SONET/SDH circuit, or carried over a network using unstructured Circuit Emulation Service (CES). Termination of specific carrier layers used between the PE and circuit emulation (CE) is performed by an appropriate network service provider (NSP).
For instructions on how to configure SAToP, see Configuring Structure-Agnostic TDM over Packet.
For a sample SAToP configuration, see Configuration Examples for Pseudowire.
Structure-Aware TDM Circuit Emulation Service over Packet-Switched Network
CESoPSN encapsulates structured (NxDS0) TDM signals as PWs over PSNs.
Emulation of NxDS0 circuits saves PSN bandwidth and supports DS0-level grooming and distributed cross-connect applications. It also enhances resilience of CE devices due to the effects of loss of packets in the PSN.
For instructions on how to configure CESoPSN, see Configuring Circuit Emulation Service over Packet-Switched Network.
For a sample CESoPSN configuration, see Configuration Examples for Pseudowire.
Transportation of Service Using Ethernet over MPLS
Ethernet over MPLS (EoMPLS) PWs provide a tunneling mechanism for Ethernet traffic through an MPLS-enabled Layer 3 core network. EoMPLS PWs encapsulate Ethernet protocol data units (PDUs) inside MPLS packets and use label switching to forward them across an MPLS network. EoMPLS PWs are an evolutionary technology that allows you to migrate packet networks from legacy networks while providing transport for legacy applications. EoMPLS PWs also simplify provisioning, since the provider edge equipment only requires Layer 2 connectivity to the connected customer edge (CE) equipment. The Cisco ASR 901 implementation of EoMPLS PWs is compliant with the RFC 4447 and 4448 standards.
For instructions on how to create an EoMPLS PW, see Configuring Transportation of Service Using Ethernet over MPLS.
When configuring an EoMPLS pseudowire on the Cisco ASR 901 , you cannot configure an IP address on the same interface as the pseudowire.
Layer 2 Tunneling Protocol, version 2 and 3 (L2TPv2 and L2TPv3) is not supported on the Cisco ASR 901 series routers.
The maximum number of CEM groups supported under each controller is four.