This document extends the Label Distribution Protocol to support the operation of Point-to-Multipoint and Multipoint-to-Multipoint Label-Switched Paths. The Security Considerations section states that the same security considerations in RFC 5036 apply. It also states that authorization mechanisms for controlling which LSRs join a given MP LSP are out of scope for this document. These seem reasonable to me. The protocol appears to be initiated by the receivers (egress nodes), which could make the design of authorization mechanisms challenging. The following comments are not directly security-related: Section 2.4.1.1 (Determining one's 'upstream LSR') recommends using an operation based on CRC32 for selecting among candidate upstream LSRs. How important is it for the selection to be uniformly distributed? CRC32 is known to have poor avalanche properties that might make it unsuitable as a hash function, even for non-cryptographic purposes. Also, there is often ambiguity when specifying the use of CRC32, even if the particular generator polynomial (e.g., the ISO/IEC 3309 32-bit FCS as specified in this document) is specified. Some common implementations omit the ones-preload and/or post-complement. The input bit ordering also needs to be specified when using CRC32 with a byte-oriented protocol. (as does the translation of the CRC remainder bit vector into an integer to perform modulo operations when used as a hash function) Editorial: * There is no normative reference for CRC32.