Re: [Hipsec] Segmentation within HIP

[Miika Komu <[e-mail]>]

Hi Samu,

On 03/26/2016 03:16 AM, Tom Henderson wrote:
>
>
> On 03/25/2016 03:49 PM, Derek Fawcus wrote:
>> Recently I've been working on middlebox s/w:  Firewalls and NAT.
>>
>> One thing this has brought home to me is just how unreliable
>> fragmentation is on the current Internet.  NAT will often simply
>> break it (such that they can not be reassembled) or just discard
>> them,  and firewalls are often set up to block them.
>>
>> As such,  almost every protocol now would seem to need protocol
>> level segmentation/fragmentation,  rather than depend up IP level
>> fragmentation.
>>
>> It struck me that it should be quite simple to extend HIP to
>> support such.
>>
>> 1) Add a Controls bit which advertises that the sender supports
>> segmentation. 2) Define a new parameter,  numbered 1 such that it
>> is first in the parameters,  and is critical. Within the parameter
>> have a seqno/identifier, offset and more segments / final segment
>> bit, possibly also a total size field.  Define some simple
>> reassembly rules,  similar to those for IP fragments, such that one
>> could reassemble a HIP packet larger than 2008 bytes if desired
>> (how big?). 3) Possibly also define a none critical parameter
>> within the non signed,  non MACed range which advertises the max
>> size packet the sender is willing to reassemble.  In fact I guess
>> this might remove the need to use a Controls bit,  since it would
>> imply the sender can reassemble.
>>
>> Then have a rule that once one party has seen the other party
>> advertise the segmentation capability within the current BEX
>> session, it is free to make use of segmentation towards that peer.
>>
>> Thoughts?
>>
>> DF
>
> Hi Derek, I don't remember the details, but in the early days of HIP,
> it was decided to avoid the burden of supporting fragmentation.  I
> guess I'd prefer to see some evidence that HIP messages are being
> fragmented in the wild before starting a work effort to add support.

do you recall how long a typical X.509 certificate can get?