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Mapping of Address and Port with Translation (MAP-T)

Understanding Mapping of Address and Port with Translation (MAP-T)

This topic provides an overview of Mapping of Address and Port using Translation (MAP-T) feature. The topic lists the benefit to service providers when used as an inline service on MX Series routers with MPC and MIC interfaces.

Benefits of Mapping of Address and Port with Translation (MAP-T)

The translation mode is advantageous in scenarios where the encapsulation overhead, or IPv6 operational practices rule out encapsulation (For example, use of IPv6-only servers, or reliance on IPv6 + protocol headers for traffic classification).

Mapping of Address and Port Using Translation (MAP-T) Terminology

  1. Border Relay (BR)—MAP-T-enabled provider edge device in a MAP domain. A BR device has at least an IPv6-enabled interface and an IPv4 interface connected to the native IPv4 network.

  2. MAP-T Customer Edge(CE)—MAP-T-enabled customer edge device in a MAP deployment.

  3. MAP domain—One or more MAP-T CE devices and BR devices connected to the same virtual link.

  4. Port Set ID (PSID)—Separate part of the transport layer port space that is denoted as port set ID.

  5. Embedded Address (EA) Bits—EA-bits in the IPv6 address identify an IPv4 prefix or address or a shared IPv4 address and a port-set identifier.

  6. Softwire—Tunnel between two IPv6 end-points to carry IPv4 packets or two IPv4 end-points to carry IPv6 packets.

  7. Softwire Initiator (SI)—Softwire at the customer end that encapsulates native packets and tunnels them to a softwire concentrator at the service provider.

  8. Softwire Concentrator (SC)—Softwire that decapsulates the packets received from a softwire initiator and sends them to their destination.

Mapping of Address and Port Using Translation (MAP-T) Functionality

The following figure illustrates a simple MAP-T deployment scenario.

Figure 1: Sample MAP-T DeploymentSample MAP-T Deployment

Figure 1 illustrates the MAP-T architecture. It consists of privately addressed IPv4 users (N and M) connected by means of MAP-T CEs to an IPv6 network that is equipped with one or more MAP-T BRs.

The MAP-T CE devices are dual stack and are capable of Network Address Port Translation (NAPT). The MAP-T CE devices connect to a MAP-T Border Relay (BR) device through an IPv6-only MAP-T network domain. The MAP-T BR device is dual stack and is connected to both a public IPv4 network and an IPv6 MAP-T network.

The MAP-T functionality is as follows:

  1. The MAP-T CE devices are capable of NAPT. On receiving an IPv4 packet from the host, the MAP-T CE device performs NAT translation on the incoming IPv4 packets. The CE device translate the public IPv4 address and ports into an assigned IPv6 MAP source address. It sends the IPv6 packet with encoded IPv4 information toward the BR.

  2. The MAP-T BR checks the source IPv6 MAP address against the configured MAP rules to ensure the correct public IPv4 address and port-range of the CE are encoded in the CE's source IPv6 MAP address. It translates the IPv6 packet into an IPv4 packet and forward it into the public domain.

In the reverse path, the incoming IPv4 packet is translated into an IPv6 packet according to MAP rules. The IPv4 destination address of the received packet is translated into an IPv6 MAP address of the CE.

Mapping of Address and Port Using Translation (MAP-T) Supported and Unsupported Features

Junos OS supports the following MAP-T features and functionality:

  • TCP/UDP/ICMPv4/ICMPv6 traffic will be forwarded.

  • Support only next-hop style of configuration for MAP-T.

  • Support maximum packet size of 9192 bytes.

The following features and functionality are not supported with the MAP-T feature:

  • IPv4/IPv6 reassembly is not supported.

  • IPv6 fragmentation is not supported.

  • Implementation of draft (non-standard) versions of RFC 7599 is not supported.

  • Interface-style MAP-T configuration is not supported.

  • MAP-T and non-MAP-T service in the same service-set is not supported.

Configuring Mapping of Address and Port using Translation (MAP-T)

This example shows you how to configure the MAP-T Border Relay (BR) solution using a next hop-based style of configuration.

To configure MAP-T:

  1. Create service interface on the device with 100g bandwidth support.
  2. Configure the dual stack service interface unit 0.
  3. Configure service interface inside the dual stack domain.
  4. Configure service interface outside the dual stack domain.
  5. Configure the IPv4-facing interface on BR.
  6. Configure the CPE-facing interface on BR.
  7. Configure the MAP-T softwire concentrator and associated parameters.
    • The MAP-T IPv4 prefix must not be

  8. Configure a softwire rule to specify the direction of traffic to be tunneled and the map-t softwire concentrator to be used.
  9. Configure the service set for map-t.

For example: