{"action":"created","issue":{"url":"https://api.github.com/repos/freifunkMUC/site-ffm/issues/14","labels_url":"https://api.github.com/repos/freifunkMUC/site-ffm/issues/14/labels{/name}","comments_url":"https://api.github.com/repos/freifunkMUC/site-ffm/issues/14/comments","events_url":"https://api.github.com/repos/freifunkMUC/site-ffm/issues/14/events","html_url":"https://github.com/freifunkMUC/site-ffm/issues/14","id":60311280,"number":14,"title":"MTU für fastd","user":{"login":"t-offline","id":4408267,"avatar_url":"https://avatars.githubusercontent.com/u/4408267?v=3","gravatar_id":"","url":"https://api.github.com/users/t-offline","html_url":"https://github.com/t-offline","followers_url":"https://api.github.com/users/t-offline/followers","following_url":"https://api.github.com/users/t-offline/following{/other_user}","gists_url":"https://api.github.com/users/t-offline/gists{/gist_id}","starred_url":"https://api.github.com/users/t-offline/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/t-offline/subscriptions","organizations_url":"https://api.github.com/users/t-offline/orgs","repos_url":"https://api.github.com/users/t-offline/repos","events_url":"https://api.github.com/users/t-offline/events{/privacy}","received_events_url":"https://api.github.com/users/t-offline/received_events","type":"User","site_admin":false},"labels":[{"url":"https://api.github.com/repos/freifunkMUC/site-ffm/labels/enhancement","name":"enhancement","color":"84b6eb"},{"url":"https://api.github.com/repos/freifunkMUC/site-ffm/labels/question","name":"question","color":"cc317c"}],"state":"open","locked":false,"assignee":{"login":"fpletz","id":114159,"avatar_url":"https://avatars.githubusercontent.com/u/114159?v=3","gravatar_id":"","url":"https://api.github.com/users/fpletz","html_url":"https://github.com/fpletz","followers_url":"https://api.github.com/users/fpletz/followers","following_url":"https://api.github.com/users/fpletz/following{/other_user}","gists_url":"https://api.github.com/users/fpletz/gists{/gist_id}","starred_url":"https://api.github.com/users/fpletz/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/fpletz/subscriptions","organizations_url":"https://api.github.com/users/fpletz/orgs","repos_url":"https://api.github.com/users/fpletz/repos","events_url":"https://api.github.com/users/fpletz/events{/privacy}","received_events_url":"https://api.github.com/users/fpletz/received_events","type":"User","site_admin":false},"milestone":null,"comments":4,"created_at":"2015-03-09T08:21:29Z","updated_at":"2015-08-30T09:41:30Z","closed_at":null,"body":"Hallo,\r\n\r\nda wir nun auch IPv6 Adressen bei den gwtest*.ffmuc.net zurückliefern, sollten wir dann aber auch die MTU für IPv6 anpassen. Der Wert 1426 ist für IPv6 zu hoch. Es dürfen maximal 1406 sein.\r\n\r\nServus\r\nChristian\r\n\r\n"},"comment":{"url":"https://api.github.com/repos/freifunkMUC/site-ffm/issues/comments/136111321","html_url":"https://github.com/freifunkMUC/site-ffm/issues/14#issuecomment-136111321","issue_url":"https://api.github.com/repos/freifunkMUC/site-ffm/issues/14","id":136111321,"user":{"login":"t-offline","id":4408267,"avatar_url":"https://avatars.githubusercontent.com/u/4408267?v=3","gravatar_id":"","url":"https://api.github.com/users/t-offline","html_url":"https://github.com/t-offline","followers_url":"https://api.github.com/users/t-offline/followers","following_url":"https://api.github.com/users/t-offline/following{/other_user}","gists_url":"https://api.github.com/users/t-offline/gists{/gist_id}","starred_url":"https://api.github.com/users/t-offline/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/t-offline/subscriptions","organizations_url":"https://api.github.com/users/t-offline/orgs","repos_url":"https://api.github.com/users/t-offline/repos","events_url":"https://api.github.com/users/t-offline/events{/privacy}","received_events_url":"https://api.github.com/users/t-offline/received_events","type":"User","site_admin":false},"created_at":"2015-08-30T09:41:30Z","updated_at":"2015-08-30T09:41:30Z","body":"Hi,\r\nich habe da mal was rauskopiert und etwas ergänzt:\r\n\r\n```\r\n###############################################################################\r\nhttp://fastd.readthedocs.org/en/v17/manual/mtu.html\r\nif possible the MTU should be chosed small enough so that IP fragmentation can be avoided.\r\nUnlike OpenVPN, fastd doesn’t support fragmentation itself, but relies on the IP stack to fragment packets when necessary.\r\n\r\nGuidelines\r\n    The basic overhead of a fastd packet in TUN mode over IPv4 is 39 Bytes when only null crypto is used and 52 Bytes for all other crypto methods\r\n    TAP mode needs 14 bytes more than TUN mode\r\n    Tunneling over IPv6 needs 20 bytes more than IPv4\r\n\r\n###\r\nYour base MTU is 1492 (like most German DSL lines) and you want to use TAP mode over IPv4 with any crypto method:\r\n    Choose 1426 bytes (1492 - 52 - 14).\r\n###\r\nYour base MTU is 1492 (like most German DSL lines) and you want to use TAP mode over IPv6 with any crypto method:\r\n    Choose 1406 bytes (1492 - 52 - 14 - 20).\r\n###\r\nYour base MTU is 1420 (like most German DSL lines with SixXS[set MTU to 1420] PPPoE IPv4 UDP AYIYA) and you want to use TAP mode over IPv6 with any crypto method:\r\n    Choose 1334 bytes (1420 - 52 - 14 - 20).\r\n###\r\nConservative choice when you want to transfer IPv6 inside the tunnel(base MTU is 1366 or 1346 ???):\r\n    Choose 1280 bytes (not relevant when you use batman-adv inside the tunnel as batman-adv will take care of the inner fragmentation!!!).\r\n###\r\nConservative choice when you don’t know anything (but assume the base MTU is at least 1280 so IPv6 can be supported; eg. SixXS default MTU setting) and want to support tunnels over IPv4 and IPv6 in TAP mode with any crypto method:\r\n    Choose 1194 bytes (1280 - 52 - 14 - 20).\r\n###\r\n\r\n###############################################################################\r\n```\r\n\r\nServus\r\nChristian\r\n\r\nP.S.\r\nhttps://github.com/freifunk-gluon/gluon/blob/11bffa59db923e976587cfa981ee4d95d1307e5b/patches/packages/routing/0003-batman-adv-decrease-maximum-fragment-size.patch\r\nDort wird also die MTU z. Z. zwangsweise auf maximal 1280 gesetzt.\r\nOb das aber so bleibt?\r\n"}}