IPv6 Source Routing for ultralow Latency

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Last updated 2017-09-12
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Routing Area Working Group                         A. Foglar, InnoRoute
INTERNET-DRAFT                                     M. Parker, Uni Essex
Intended status: EXPERIMENTAL                        T. Rokkas, Incites
Expires: March 11, 2018                              September 12, 2017     

          IPv6 Source Routing for ultralow Latency


  This Internet-Draft describes a hierarchical addressing scheme 
  for IPv6, intentionally very much simplified to allow for very 
  fast source routing experimentation using simple forwarding 
  nodes. Research groups evaluate achievable latency reduction 
  for special applications such as radio access networks, 
  industrial networks or other networks requiring very low 
Status of This Memo

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  material or to cite them other than as "work in progress."

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  Copyright (c) 2017 IETF Trust and the persons identified as 
  the document authors. All rights reserved.
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  described in the Simplified BSD License.

1. Introduction

  To achieve minimum latency the forwarding nodes must support 
  cut-through technology as opposed to the commonly used store-
  and-forward technology. Cut-through means, that the packet 
  header already leaves a node at the egress port while the tail 
  of the packet is still received at the ingress port. This 
  short time does not allow complex routing decisions. 
  Therefore, a very simple routing address field structure is 
  specified below. It should limit the complexity of the 
  forwarding node used in the experiments. Therefore, in this 
  text the term "forwarding node" is used instead of "router", 
  although the device is operating in OSI Layer 3 and accordingly
  executes router functions such as decrementing the hop limit field.
  Redundancy issues are not considered. 

2. IPv6 address prefix structure

  One of the goals of IPv6 was to have a sufficiently long address 
  to allow grouping in fields to simplify routing decisions. In 
  this proposal, this goal is exploited to allow for very low 
  complexity in the forwarding nodes. 
  Each forwarding node has up to 16 ports and hence needs 4 bits 
  of the address field to decide to which port a packet should 
  be forwarded. The 64-bit prefix is divided into 16 sub-fields 
  of 4 bit, defining up to 16 hierarchy levels. A forwarding 
  node is configured manually to which of the sub-fields it should
  evaluate for the forwarding decision. 
  A number n of leading 4-bit fields cannot be used for forwarding 
  decisions, but must have a special value to indicate the 
  'escape prefix' of the experimental forwarding mode. 
  The 64-bit prefix of the IPv6 address has this structure:
  | n x 4-bit escape prefix |(16-n) x 4-bit address fields |
  The first 4-bit field following the escape prefix has the 
  highest hierarchy level, the last 4-bit field has the lowest 
  hierarchy level.

3. Forwarding node behavior

  The forwarding node has up to 16 downlink ports and at least 
  one uplink port. Typically, the forwarding nodes are arranged 
  in a regular tree structure with one top node, up to 16 nodes 
  in the second hierarchy, up to 256 nodes in the third hierarchy 
  and so on for up to 16-n hierarchies.
  A forwarding node must be configured to operate at a certain 
  position in the hierarchical network. For example, at third 
  hierarchy level, branch 4 of the first hierarchy and branch 12 
  of the second hierarchy. 
  The behavior of each forwarding node is depending on the 
  position of a node in a hierarchical network. For all 
  positions, the first step is to check the escape prefix. Only 
  packets with matching escape prefix are forwarded. 
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