The best replacement for avaya is cisco.

The best alternatives to avaya are rated as following:
★★★★★  cisco
★★★  shoretel
★★  nec
★★  cisco voip
★★  mitel
★★  nortel
★  asterisk
★  lync
★  continuant
★  genesys
★  polycom
★  interactive intelligence
  aspect
  cisco call center
  siemens
  allworx
  cisco ip pbx
  alcatel
  inter tel
  cisco ip telephony
  cisco phone system
  cisco call manager
  cisco uc
  microsoft lync
  tli
  3com

Your alternative for avaya is not listed? Suggest!
Speaking about avaya, one probably shouldn't forget about lync.

Other search terms related to avaya and their ratings are:
★★★★★ lync
★★ nortel
★★ polycom
★★ siebel
You have in mind a companion for avaya and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of avaya in all years. Click on graph for more.
avaya
cisco
shoretel