Subject: [v6ops] draft-jiang-v6ops-semantic-prefix-02

From: Brian E Carpenter <[email-masked]>
Date: Tue, 05 Mar 2013 15:18:20 +0000

Hi,

One thing I don't understand, and one comment.

Consider the first example:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           IANA assigned block         |      locator          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        locator (Cont.)        | Semantic Field|Subscriber bits|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   An ISP semantic prefix example

What happens if a subscriber happens to operate two servers (which
should be quite common in IPv6, where "subscriber" does not mean
"client")? One server is, say, a video server so that the user
can look at a security camera remotely (i.e. a high-speed loss-tolerant
QoS is required). The other server is a building services proxy,
so that the use can check the room temperature and change the
thermostat (i.e. a low speed elastic QoS is sufficient). Both these
servers will get the same "semantic field". So how will this help
with their QoS requirements?

My comment is that there needs to be a discussion of address
utilisation. An ISP is given a /20 because it was justified by
their customer numbers, assuming a certain rate of address
utilisation. How much address space will be wasted as a result
of the semantic field? Will the ISP need to go back to its
registry for more space sooner than expected?

Regards
   Brian Carpenter

---

From: Sheng Jiang <[email-masked]>
Date: Wed, 6 Mar 2013 04:01:54 +0000

Hi, Brian,

Thanks for your comments. Please see my replies in lines.

>Consider the first example:

If the semantic has been designed to be application-aware. The single subscriber would be identified as two different connection requests. Two different prefix will be given with different semantic field. This kind of use case does not by the current protocols. We have described some technical gaps in order to fulfill such use case.

>registry for more space sooner than expected?

I agree with you that semantic embedded will lower the address utilization rate. However, the address allocation is not only according to the customer numbers, I believe. There are already many cases that address space are consumed based on network topologies/strategies/functions, etc., such as mobile support. They are already semantic in some sense. Semantic prefix is a similar efforts. The only different is we are trying to give a generic framework and guidance.

Best regards,

Sheng

>Regards
>   Brian Carpenter
>
>
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