RE: draft-bonica-tunneltrace-02

[Shahram Davari <Shahram_Davari@pmc-sierra.com>]

Eric,
> 
> Thanks for extracting Dave's note on security issues; I 
> apologize for having
> missed that in  the noise.  That is certainly a reasonable  
> set of issues to
> discuss before turning the GTTP document into a Proposed Standard. 

Good.

> 
> I don't think your compatibility issues are valid.
> 
> > It is not compatible with RFC792 and RFC1122. 
> 
> > 1) RFC792 says: 
> 
> > "If the gateway processing a datagram finds the time to 
> live field is zero
> > it must discard the datagram" 
> 
> > GTTP draft says: 
> 
> > On TTL expiration forward the GTTP messages to a local GTTP module. 
> 
> I'm not sure  that I see what the incompatibility is;  
> "discard a packet" is
> generally interpreted as  meaning "do not continue to  
> forward the packet to
> its destination address". 
> 
> If you  can show  an interoperability  problem of some  sort, 
> that  would be
> interesting.

Here they are:

1)If a router is not GTTP upgraded, it will drop the TTL expired GTTP messages. 
Consequently the host will not receive any reply from that router, which 
translates to a break in the tunnel at that point.

2)TTL expired user packets will now be forwarded to UDP module instead of being
dropped. Which could overload the UDP module in certain situations.


> 
> > 2) RFC1122 says: 
> 
> > "An incoming Time Exceeded message MUST be passed to the 
> transport layer." 
> 
> > GTTP draft says: 
> 
> > "The error-processing module sends an  ICMP Time Expired 
> Message to D1. D1
> > discards this ICMP message."
> 
> RFC1122  is  not   meant  to  apply  to  routers. 
 
Yes it does. Actually RFC 1812 (router requirements) references 1122.

> Even   so, 
>  there  is  no
> incompatibility, because it is not the IP layer at D1 that is 
> discarding the
> message, but  the higher layer.  Perhaps  what the doc should 
>  really say is
> that GTTP should discard the ICMP Time Expired Messages.


OK. 


> 
> On  the issue of  layer violations,  I think  that if  you 
> cannot  state the
> problem   in  practical   terms,  without   using  the   
> words   "layer"  or
> "architecture", then there is no problem.
> 

I am working on examples. I will send it to you later.

-Shahram