Hi Ron,

We use the next header value 59 to identify at the receiver that there is no 
other kind of Internet Protocol beneath to be processed. 
Note that we are *not* using 59 to identify the fact that it is an ethernet 
header (i.e. other non Internet-Protocols would also use the 59 to identify 
that no further IP header processing has to be performed). The SID identifies 
that an Ethernet header follows the IPv6 extension headers.

Thanks,
Pablo.

-----Original Message-----
From: ipv6 <ipv6-boun...@ietf.org> on behalf of Ron Bonica 
<rbonica=40juniper....@dmarc.ietf.org>
Date: Monday, 6 May 2019 at 02:48
To: SPRING WG <spring@ietf.org>, 6man WG <i...@ietf.org>
Subject: SRv6 Network Programming: ENH = 59

    Folks,
    
    According to Section 4.4 of draft-ietf-spring-srv6-network-programming-00, 
when processing the End.DX2 SID, the Next Header must be equal to 59. 
Otherwise, the packet will be dropped.
    
    In the words of the draft, "We conveniently reuse the next-header value 59 
allocated to IPv6 No Next Header [RFC8200].  When the SID corresponds to 
function End.DX2 and the Next-Header value is 59, we know that an Ethernet 
frame is in the payload without any further header."
    
    According to Section 4.7 RFC 8200, " The value 59 in the Next Header field 
of an IPv6 header or any  extension header indicates that there is nothing 
following that header.  If the Payload Length field of the IPv6 header 
indicates the presence of octets past the end of a header whose Next Header 
field contains 59, those octets must be ignored and passed on unchanged if the 
packet is forwarded."
    
    Does the WG think that it is a good idea to reuse the Next Header value 59? 
Or would it be better to allocate a new Next Header value that represents 
Ethernet?
    
                                                              Ron
    
    
    Juniper Internal
    
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