Storer, B., Pignataro, C., Ed., Dos Santos, M., Stevant, B., Ed., Toutain, L., and J. Tremblay, "Softwire Hub and Spoke Deployment Framework with Layer Two Tunneling Protocol Version 2 (L2TPv2)", RFC 5571, DOI 10.17487/RFC5571, June 2009, <https://www.rfc-editor.org/info/rfc5571>.