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Re: Comments on latest IPSP drafts
At 12:24 PM 4/10/95 -0700, Hilarie Orman wrote:
>>I suggest that there should be a discussion of the impact of IP
>>fragmentation. In particular: (a) performance is affected since IP packets
>>that already equal the MTU size will overflow with the addition of the AH or
>>ESP data; (b) I think there should be an implementation note that the
sender of
>>an IPSP packet should make sure to put it through the fragmentation process,
>>and the destination of an IPSP packet must reassemble it before processing the
>>AH header or ESP payload.
>
>In our prototyping of an IP security layer, we approached this by
>having the sender's query for the MTU be intercepted by the security
>layer, which subtracts the header lengths from the actual network MTU.
>The sender thus learns how much payload is available. The
>implementation of security as a layer makes the frag/reassembly
>constraint natural and obvious.
But this does not help a user of a PPP dialup link that was getting 24Kb
throughput from a V.32bis modem and now is getting 14Kb. That is a REAL
degredation of throughput, much worst than what we have been talking about
for Ethernet based users. And remember, there is also ISDN compression...
Robert Moskowitz
Chrysler Corporation
(810) 758-8212