The route manual page
The netstat manual page
The arp manual page
The ifconfig manual page
Alexej Kuznetsov's TEQL Linux source file sch_teql.c (included in the Linux sources)
RFC 2991, "Multipath Issues in Unicast and Multicast Next-Hop Selection"
RFC 2992, "Analysis of an Equal-Cost Multi-Path Algorithm"
PPP Multilink /usr/src/linux/Documentation/networking/ppp_generic.txt
RFC 1990, "PPP Multilink Protocol (MP)"
RFC 2125, "PPP Bandwidth Allocation Protocol?Supports unlimited Number of ML-PPP Bundles"