Not all versions of DMT are the same and not all will display all those options.
I'm not certain, but I think if you leave them blank they are left at default settings by the router
Lpair = Loop Pair. lpair<(i)nner|(o)uter>
(i)nner- inner loop pair is used
(o)uter- outer loop pair is used
Dont touch - but Inner is the default
TrellisShould normally be on - Trellis improves the stability of your line with little overhead.
More information on
Trellis Coded Modulation on the main site.
Something worthy of note is that if Interleaving and Reed Soloman encoding is applied on your line, then trellis may not always be recognised/reported by the router.
Trellis and RS coding can be combined with TCM being the inner code.
BitwapShould be on particularly for rate adaptive lines. Without bitswapping your line would soon loose connection if your SNR dropped too low.
More info on
bitswapping on the main site.
SRA - Seamless Rate AdaptionDefault = Off
Currently only used in the UK by UKOnline. SRA is the dynamic adaptation of sync speed according to line conditions.
More info on
Seamless Rate Adaption (SRA) on the main site.