Entropy Labels Shane Amante Kireeti Kompella What ECMP

Entropy Labels Shane Amante Kireeti Kompella

What • ECMP is a powerful tool for SPs: make it better • At the ingress of an LSP, assign “entropy labels” to incoming traffic such that packets from the same “flow” get the same label • At transit LSRs, use the label stack (including entropy label) to make good ECMP decisions • At the egress, discard the entropy label

Why • Of all the LSRs in the path, the ingress LER is best positioned to identify separate flows – It has the most “context” about incoming traffic, (i. e. : expected encapsulation on incoming port) – It receives packets with least overhead (simplest to parse and extract juicy bits) – So, ingress LER gets to do a bit more work • Transit LSRs have less context, more encaps overhead and much higher data rates – So, transit LSRs get to do less work

Examples • Incoming “traffic trunk” is an IP-in-IP or L 2 TP tunnel, to be carried over an LSP – Juicy bits are beyond the TCP ports • Incoming traffic trunk is an IP VPN – Juicy bits are “behind” a two-label stack • Incoming traffic trunk is an IPsec tunnel, again to be carried over an LSP – Juicy bits are in IPsec packet header (or encrypted)

Who • Level 3 and Deutsche Telekom have expressed strong interest • Other service providers have expressed interest, although not always publicly • Several others have shown interest in entropy labels, in one context or other (e. g. , PWs)

Goals of this doc 1. Define general characteristics of entropy labels – Ingress-assigned? Signaled? Shielded? – Ensure they are not mixed up with “regular” labels – Define how they are to be treated in the forwarding path on ingress, transit and egress LSRs

Goals of this doc 2. Define signaling for entropy labels to use with LDP and RSVP-TE LSPs 3. Farm off “application-specific” use and signaling of entropy labels to other WGs – PWE 3, L 3 VPN, …

Next Steps • Figure out what to do among the various proposals for entropy labels – Find a more PC name for “fat PWs” – Google “entropy label” and “hash label”, and resolve brothers’ fight before it gets serious – Have interim meeting in Amsterdam coffee shop to, um, hash out all issues • Start work on MIB to manage entropy labels • Find steganographic application of entropy labels so Security Directorate forever bans their use

Acknowledgments • George, Vach, Wim, Stewart & others • Many thanks to the “fat PW” authors for starting this excellent work, and the “hash label” authors for their part • Thanks, too, to the group of “hashers” who provided, for a brief instant, a useful discussion of issues, then went back to sleep – Here’s hoping they rise again!