proposal 127

i2p2www/spec/proposals/127-increase-ipv6-mtu

@@ -0,0 +1,54 @@
+=================
+Increase IPv6 MTU
+=================
+.. meta::
+    :author: zzz
+    :created: 2016-08-23
+    :thread: http://zzz.i2p/topics/2181
+    :lastupdated: 2016-08-23
+    :status: Open
+
+.. contents::
+
+
+Overview
+========
+
+This proposal is to increase the max SSU IPv6 MTU from 1472 top 1488.
+
+
+Motivation
+==========
+
+IPv4 MTU must be a multiple of 16, + 12. IPv6 MTU must be a multiple of 16.
+
+
+When IPv6 support was first added years ago, we set the max IPv6 MTU to 1472, less than the
+IPv4 MTU of 1484. This was to keep things simple and ensure the IPv6 MTU was less
+than the existing IPv4 MTU. Now that IPv6 support is stable, we should be able to
+set the IPv6 MTU higher than the IPv4 MTU.
+
+The typical interface MTU is 1500, so we can reasonably increase the IPv6 MTU by 16 to 1488.
+
+
+Design
+======
+
+Change the max from 1472 to 1488.
+
+
+Specification
+=============
+
+In the "Router Address" and "MTU" sections of the SSU overview,
+change the max IPv6 MTU from 1472 to 1488.
+
+
+Migration
+=========
+
+We expect that routers will set the connection MTU as the minimum of the local and remote
+MTU, as usual. No version check should be required.
+
+If we determine that a version check is required, we will set a minimum version
+level of 0.9.28 for this change.