From 2ef49eb3bd8e3fa4c345a67585606135f964d53b Mon Sep 17 00:00:00 2001 From: Gregory Nutt Date: Sun, 18 Jun 2017 09:01:18 -0600 Subject: [PATCH] Update TODO and README --- TODO | 21 ++++++++++++--------- net/sixlowpan/README.txt | 33 ++++++++++++++++++++++++++++++++- 2 files changed, 44 insertions(+), 10 deletions(-) diff --git a/TODO b/TODO index 1cac77e862..f5975ae90b 100644 --- a/TODO +++ b/TODO @@ -1234,14 +1234,14 @@ o Network (net/, drivers/net) Title: ICMPv6 FOR 6loWPAN Description: The current ICMPv6 and neighbor-related logic only works with - Ethernet MAC. For 6loWPAN, a new more conservative ICMPv6 - definitions is provided by RFC 6775. This RFC needs to be - supported in order to support ping6 on a 6loWPAN network. + Ethernet MAC. For 6loWPAN, a new more conservative IPv6 + neigbor discovery is provided by RFC 6775. This RFC needs to + be supported in order to support ping6 on a 6loWPAN network. If RFC 6775 were implemented, then arbitrary IPv6 addresses, including addresses from DHCPv6 could be used. can - UPDATE: With ICMPv6 neighbor discovery, any IPv6 address may + UPDATE: With IPv6 neighbor discovery, any IPv6 address may be associated with any short or extended address. In fact, that is the whole purpose of the neighbor discover logic: It plays the same role as ARP in IPv4; it ultimately just manages @@ -1256,15 +1256,18 @@ o Network (net/, drivers/net) Most of the 6loWPAN compression algorithms exploit this to compress the IPv6 address to nothing but a bit indicating that the IP address derives from the node address. So I - think ICMPv6 is useless in the current implementation. + think IPv6 neighbor discover is useless in the current + implementation. - If we want to use ICMPv6, we could dispense with the all MAC - based addressing. But if we want to retain the more compact - MAC-based addressing, then we don't need ICMPv6. + If we want to use IPv6 neighbor discovery, we could dispense + with the all MAC based addressing. But if we want to retain + the more compact MAC-based addressing, then we don't need + IPv6 neighbor discovery. So, the full neighbor discovery logic is not currently useful, but it would still be nice to have enough in place to support - ping6. + ping6. Full neighbor support would probably be necessary if we + wanted to route 6LoWPAN frames outside of the WPAN. Status: Open Priority: Low for now. I don't plan on implementing this. It would diff --git a/net/sixlowpan/README.txt b/net/sixlowpan/README.txt index 9eb848144e..4031af925d 100644 --- a/net/sixlowpan/README.txt +++ b/net/sixlowpan/README.txt @@ -1,4 +1,35 @@ -Optimal 6loWPAN Configuration +6LoWPAN Addressing +------------------ + +The current 6LoWPAN implementation uses only link local, MAC-based +addressing addressing (as discussed in more detail below). Thus if you know +the node addressing, then you know the IPv6 address (and vice-versa) + +IPv6 Neighbor Discovery is not supported. The current ICMPv6 and neighbor- +related logic only works with Ethernet MAC. For 6LoWPAN, a +new more conservative IPv6 neigbor discovery is provided by RFC 6775 which +is not currently suppored. With IPv6 neighbor discovery, any IPv6 address +may be associated with any short or extended address. In fact, that is the +whole purpose of the neighbor discover logic: It plays the same role as ARP +in IPv4; it ultimately just manages a neighbor table that, like the arp +table, provides the mapping between IP addresses and node addresses. + +The NuttX, Contiki-based 6LoWPAN implementation circumvents the need for +the neighbor discovery logic by using only MAC-based addressing, i.e., the +lower two or eight bytes of the IP address are the node address. + +Most of the 6LoWPAN compression algorithms exploit this kind of addressing +to compress the IPv6 address to nothing but a single bit indicating that the +IP address derives from the node address. In this use case, IPv6 neighbor +discover is not useful: If we want to use IPv6 neighbor discovery, we could +dispense with the all MAC based addressing. But if we want to retain the +more compact MAC-based addressing, then we don't need IPv6 neighbor discovery. + +However, it would still be nice to have enough in place to support ping6. +Full neighbor support would be necessary if we wanted to route 6LoWPAN frames +outside of the WPAN. + +Optimal 6LoWPAN Configuration ----------------------------- 1. Link local IP addresses: