From c84ca7474bcdc076668c8cda2282300df49a936d Mon Sep 17 00:00:00 2001 From: Tomek Mrugalski Date: Fri, 25 Sep 2020 14:18:25 +0200 Subject: [PATCH] [#1351] Added doc section --- doc/sphinx/arm/dhcp4-srv.rst | 42 ++++++++++++++++++++++++++++++++++++ 1 file changed, 42 insertions(+) diff --git a/doc/sphinx/arm/dhcp4-srv.rst b/doc/sphinx/arm/dhcp4-srv.rst index 1960c2f713..796323893e 100644 --- a/doc/sphinx/arm/dhcp4-srv.rst +++ b/doc/sphinx/arm/dhcp4-srv.rst @@ -3855,6 +3855,43 @@ Our tests reported best results when: - ``packet-queue-size``: 11 * ``thread-pool-size`` when using ``postgresql`` for storing leases. In our case it's 11 * 8 = 88. +IPv6-only Preferred Networks +---------------------------- + +A recent Internet-Draft `draft-ietf-dhc-v6only +`_ soon to be published by IETF as +RFC specifies a DHCPv4 option to indicate that a host supports an IPv6-only mode and is willing to +forgo obtaining an IPv4 address if the network provides IPv6 connectivity. The general idea is that +a network administrator can enable this option to signal to compatible dual-stack devices that the +IPv6 connectivity is available and they can shut down their IPv4 stack. The new option +`v6-only-preferred` is expressed as 32 bit unsigned integer and expressed for how long the device +should disable its stack for. The value is expressed in seconds. + +The draft mentions V6ONLY_WAIT timer. This is implemented in Kea by setting the value of +v6-only-preferred option. This follows the usual practice of setting options. You can specify the +option value on pool, subnet, shared network, global levels or even specify it in host reservations. + +Note there is no special processing involved. This follows the standard Kea option processing +regime. The option will not be sent back, unless the client explicitly requests it. For example, to +enable the option for the whole subnet, the following configuration can be used: + +:: + + "subnet4": [ + { + "pools": [ { "pool": "192.0.2.1 - 192.0.2.200" } ], + "subnet": "192.0.2.0/24", + "option-data": [ + { + // This will make the v6-only capable devices to disable their + // v4 stack for half an hour and then try again + "name": "v6-only-preferred", + "data": "1800" + } + ] + } + ], + .. _host-reservation-v4: Host Reservation in DHCPv4 @@ -6121,6 +6158,11 @@ The following standards are currently supported: message, remembers the UDP port and sends back reply to the same relay agent using this UDP port. +- *IPv6-Only-Preferred Option for DHCPv4*, `draft-ietf-dhc-v6only-08 + `__: The Kea + server is able to designate its pools and subnets as v6only-preferred and send + back the `v6-only-preferred` option to clients that requested it. + .. _dhcp4-limit: DHCPv4 Server Limitations