SPRING Working Group

Instead of forwarding to a specific device or to all devices in a group, anycast addresses, let network devices forward a packet to (or steer it through) one or more topologically nearest devices in a specific group of network devices. The use of anycast addresses has been extended to the Segment Routing (SR) network, wherein a group of SR-capable devices can represent a anycast address, by having the same Segment Routing Global Block (SRGB) provisioned on all the devices and each one of them advertising the same anycast prefix segment (or Anycast SID). This document describes a proposal for implementing anycast prefix segments in a MPLS-based SR network, without the need to have the same SRGB block (label ranges) provisioned across all the member devices in the group. Each node can be provisioned with a separate SRGB from the label range supported by the specfic hardware platform. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute Sarkar, et al. Expires October 15, 2016 [Page 1] Internet-Draft Anycast Segments in MPLS-based SR April 2016 working documents as Internet-Drafts. The list of current InternetDrafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on October 15, 2016.