Subject: Re: MPLS WG Last Call draft-ietf-mpls-in-ip-or-gre-00.txt

From: Mark Duffy <[email-masked]>
Date: Fri, 11 Apr 2003 17:38:33 -0400

>This message begins an MPLS Workgroup last call on
>
>   Encapsulating MPLS in IP or GRE
>     draft-ietf-mpls-in-ip-or-gre-00.txt

Hi, I have a few questions/comments on the draft.

1.  In section 2 there are protocol numbers 'X' and 'Y' called out.  I 
presume these are to be replaced with values assigned by IANA.  I don't 
know what the politics are by which values get assigned or denied but since 
the 'Y' value for MPLS multicast "is for further study" perhaps IANA should 
only be asked for an 'X' value at this time.  I should think a request for 
one value is more likely to succeed than a request for two.

2.  In sect 4.1, there is a clear implication that the "Tunnel MTU" 
describes the maximum sized *MPLS packet* that can be encapsulated in the 
IP or GRE packet.  Therefore I think the following paragraph is not quite 
correct:

    In some cases, the tunnel head receives, for encapsulation, an IP
    packet, which it first encapsulates in MPLS and then encapsulates in
    MPLS-in-IP or MPLS-in-GRE.  If the source of the IP packet is
    reachable from the tunnel head, and if the result of this
    encapsulation would be a packet whose size exceeds the Tunnel MTU,
    then the tunnel head SHOULD use the Tunnel MTU value for the purposes
    of fragmentation and PMTU discovery outside the tunnel.

I think it should instead read something like:

    In some cases, the tunnel head receives, for encapsulation, an IP
    packet, which it first encapsulates in MPLS and then encapsulates in
    MPLS-in-IP or MPLS-in-GRE.  If the source of the IP packet is
    reachable from the tunnel head, and if the result of **the MPLS**
    encapsulation would be a packet whose size exceeds the Tunnel MTU,
    then the tunnel head SHOULD use the Tunnel MTU value, **less the size
    of the added MPLS label stack,** for the purposes of fragmentation
    and PMTU discovery outside the **MPLS LSPs and encapsulating** tunnel.

3.  A few typos:

In the last sentence of sect. 2 and the exact same text again at the last 
sentence of sect. 3:  s/is the topmost packet of the decapsulated packet/is 
the topmost label of the decapsulated packet/

In sect 4.1  s/mpls packet be decapsulated/mpls packet can be decapsulated/

In sect 8 s/RFC7915/RFC791/

Thanks,
Mark