doc/technical/ts5.txt

   1   Overview of the TS5 system
   2   Lee H <lee@leeh.co.uk>
   3
   4 $Id: ts5.txt 6 2005-09-10 01:02:21Z nenolod $
   5
   6 For the purposes of this document, ircd versions:
   7   hybrid6.0
   8   ircd-comstud-1.12
   9   CSr31pl4
  10
  11 and prior, are TS3.
  12
  13 ircd-hybrid-6.2 and later support TS5.
  14
  15
  16 Whats TS5?
  17 ----------
  18
  19 The difference between TS5 and TS3 is what happened on opless channels.  TS
  20 works by establishing which server has the oldest version of the channel,
  21 the version that is oldest, keeps its modes and ops, the version that is
  22 youngest, removes their modes and ops, and accepts the older version.
  23
  24 There was an exception to this rule with opless channels, if a channel was
  25 opless, TS3 would allow anybody to keep their ops and modes on the channel.
  26 TS5 aims to stop this, by removing this exception.
  27
  28 Example1:
  29
  30 An irc network, with server A (every server is ts3)
  31
  32 UserA is on ServerA, in channel #broken.  This channel is opless, and has a
  33 TS of 800000000.  ServerA splits, and whilst it is split, UserA cycles
  34 channel #broken, recreates the channel and is given ops.  On ServerA #broken
  35 now has a TS of 900000000 and has ops.  ServerA rejoins with the network,
  36 via HubB.  HubB realises #broken is opless, so allows UserA to retain ops.
  37 The TS is moved forward to 900000000.
  38
  39 The network now sees #broken as having a TS of 900000000, with UserA being
  40 opped.
  41
  42 Example2:
  43
  44 An irc network, with server C (every server is ts5)
  45
  46 Same scenario as above.  ServerC splits and UserC cycles channel #broken,
  47 recreating it with a TS of 900000000.  ServerC rejoins with the network via
  48 HubD.  HubD realises #broken has a TS of 800000000 locally, and ServerC is
  49 showing a TS of 900000000, it ignores ServerC's modes and ops.  The channel
  50 remains opless.  ServerC receives HubD's modes, and it notices HubD has a
  51 lower TS of channel #broken.  It removes UserC's ops, removes the channel
  52 modes on #broken, and accepts HubD's status.
  53
  54 The network version of #broken hasnt changed.  It is still opless, with a TS
  55 of 800000000.
  56
  57
  58 As you can see, TS5 makes splitting a server to regain ops useless, as it
  59 cannot be abused to give ops after a netsplit.
  60
  61 The problem with TS5 however, is what happens on a mixed TS5/TS3 network.
  62 Channels where the older TS has ops will behave the same way on TS5 and TS3,
  63 however an opless channel will behave differently, as you can see above.
  64
  65 The result of TS5/TS3 mixed can be a desync:
  66
  67 Example1:
  68
  69 As per Example1 above, except the rest of the network is TS5, ServerA is
  70 TS3.  ServerA would keep its modes and ops, whilst the rest of the network
  71 would remove them.  This means only ServerA would see UserA as opped.  The
  72 desync can be abused, as UserA can send modes.  Hybrid6.0 servers will
  73 accept these modes from the unopped client, so if UserA ops UserB, who then
  74 ops UserA, the channel will be the same across all Hybrid6.0 and Hybrid6.1
  75 servers.
  76
  77 Example2:
  78
  79 As per Example2 above, except the rest of the network is TS3.  ServerC is
  80 TS5.  ServerC would remove its modes and ops, therefore UserC would not be
  81 opped on ServerC, therefore it could not send any mode changes to the
  82 channel.  Although it is opped elsewhere, it isnt opped locally, so the
  83 desync cannot be abused.
  84
  85 As you can see, the desync's that can occur can either be resynced, or are
  86 useless to the user, so a mixed TS5/TS3 network is not a huge problem,
  87 although a desync is NOT a good thing to have.
  88
  89
  90 Why TS5?
  91 --------
  92
  93 We have jumped to TS5 from TS3, because there was a version of ircd that was
  94 TS4, so it was thought better to avoid a clash with an existing version.
  95
  96
  97 Advantages
  98 ----------
  99
 100 Its a realistic event that a server will be attacked so it splits off a
 101 network, then used to regain ops in a channel.  TS5 makes this pointless,
 102 the server will never give ops on a netsplit.  TS5 is network wide, so it
 103 leaves individual servers free to choose options like NO_JOIN_ON_SPLIT,
 104 whilst keeping splits useless to users.
 105
 106
 107 Disadvantages
 108 -------------
 109
 110 Its virtually impossible for a user to actively regain ops themselves (some
 111 regard this as an advantage..) because on a large sized channel, its
 112 impossible to get people to leave so it can be recreated, therefore if a
 113 network did not have some form of services, it could possibly end up
 114 requiring oper intervention, as you cant get everybody to leave, and you
 115 cant use splits to regain ops, therefore if the channel is open (an
 116 invite-only channel would gradually destroy itself as noone new can join) it
 117 could be impossible for a user to regain ops.
 118
 119 On a network that has some form of services, The effect of TS5 would be
 120 minimal, however the services must be of sufficient quality to fix opless
 121 channels, as TS5 renders netsplits for ops worthless.
 122
 123
 124 Recommendations
 125 ---------------
 126
 127 If your network has good stable services, we recommend TS5 is enabled, as
 128 people have no reason to abuse netsplits anyway.
 129
 130 If your network has no services at all, then TS5 may cause problems with
 131 users being left with a permanently opless channel.
 132
 133 If your network occupies the middle ground, then its a choice between users
 134 needing to be able to use splits to regain ops, or making netsplits that are
 135 caused to regain ops worthless.
 136
 137 If TS5 is chosen, the FULL network must upgrade and this should be done in a
 138 relatively short space of time to minimise the possible desync effects.
 139
 140
 141 Alternatives
 142 ------------
 143
 144 There is also NO_JOIN_ON_SPLIT and NO_OP_ON_SPLIT, however these use the
 145 configuration of minimum servers and users, and sometimes a split that is
 146 above these limits is enough to be abused to regain ops, whereas if the
 147 limits are too high, clients will never be able to join anything or be opped
 148 when they create a channel.
 149
 150
 151 EOF