This text field, delivered as part of an SNMP notification, identifies which routing protocol, BGP, LDP, or an unrecognized one, is using TCP MD5 authentication on the connection the notification concerns. An administrator reads this to immediately know which protocol's TCP session the alert is about, since both BGP and LDP commonly rely on MD5-authenticated TCP sessions and a notification about an authentication problem needs to specify which. For example, this field containing the value "BGP" tells the administrator the notification concerns an MD5-authenticated BGP TCP session specifically, not an LDP one.