What’s a Steiner Tree?

Any of you who have worked with VPLS or NG-MVPNs are likely already familiar with using Point-to-Multipoint (P2MP) LSPs to get traffic from a single ingress PE to multiple egress PEs.  The reason that P2MP LSPs are desired in these cases is that it can reduce unnecessary replication by doing so only where absolutely required, for example where a given P2MP LSP must diverge in order to reach two different PEs.

However, typically the sub-LSPs which are part of a given P2MP LSP traverse the shortest-path from ingress to egress based on whatever user defined constraints have been configured.  While this is fine for many applications, additional optimizations might be required such that additional bandwidth savings can be realized.

We will take a look at something called a Steiner-Tree which can help the network operator to realize these additional savings, when warranted, reducing the overall bandwidth used in the network and fundamentally changing the way in which paths are computed. Continue reading “What’s a Steiner Tree?”

Preparation Tips for the JNCIE-SEC Exam

Not a day that goes by since having passed the JNCIE-SEC exam that I don’t receive an inquiry in one form or another regarding how I prepared for the exam.  It seems that there is an incredible amount of interest in this exam, especially from all those die-hard ScreenOS folks that are now converting to Junos.  So instead of constantly repeating myself, I figured I’d just put it up on the blog so others can benefit (leaving me more time to do other things, ‘heh).

Continue reading “Preparation Tips for the JNCIE-SEC Exam”