If you IOS supports these MIBs 'show dsl int atmx/y' normally is mapped, for
ADSL, using adslAtucChanCurrTxRate -- downstream and
adslAturChanCurrTxRate -- upstream. These are from the ADSL-LINE-MIB.my
mib. There is also CISCO-IETF-VDSL-LINE-MIB.my that has
cvdslLineConfRxSpeed and cvdslLineConfTxSpeed that look like candidates
for other forms of DSL as well if this is not ADSL type of setup