hello,
On 07/26/2016 02:59 AM, Xing Li wrote:
[email protected] ει:
Normen,
I just want to make sure that I'm not misunderstanding this:
RFC 7597, section 6 describes the last 16 Bits of the construction
of the Ipv6 interface identifier as follows:
The PSID field is left-padded with zeros to create a 16-bit field.
RFC7598 Section 5.1. describes the format for provision the PSID to
clients with the following text:
o PSID: 16 bits long. The PSID value algorithmically identifies
a set of ports assigned to a CE. The first k bits on the left of
this field contain the PSID binary value. The remaining (16 - k)
bits on the right are padding zeros.
To me this seems that the two RFCs use two different formats to
express the same information in a field with the same name.
Lets assume an example where the port split ratio is 6 (=k), slicing
the IPv4 address up into up 2**6 = 64 slices, each segment having
1024 ports.
In RFC 7597, to select the third port-range, the parameters become
OFFSET 0, PSID-LEN 6, PSID 0x2 (left padded with zeros to 16 bits)
In RFC 7598, to select the third port-range, the parameters become
OFFSET 0, PSID-LEN 6, PSID 0x800 (leftmost k-bits on this field
contain the PSID binary value, which is right padded with zeros to
fit 16 bits)
So,
1, Is my understanding of the two RFC's PSID formats correct?
I believe so.
2, What's the reason for the difference in the formats?
Good question. The 7597 PSID in the IID is mainly there for pretty
printing / troubleshooting, and it makes sense to left pad it.
I can only guess about the 7598 format, possibly to keep the PSID
field consistent with the other fields (prefix) which are all right
padded.
this might create some confusion about the way the lwB4 will construct
the IID for the tunnel endpoint (use "2" or "800" for the last 16 bits?)
I agree with Ole. For your information, our implementation has a
configuration function to select the format of PSID. Regards, xing
where is this function implemented?
best regards,
Yannis
Best regards,
Ole
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Yannis Nikolopoulos OTE S.A
e-mail: [email protected] IP Network Planning & Engineering
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