[email protected] 写道:
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.
I agree with Ole. For your information, our implementation has a
configuration function to select the format of PSID. Regards, xing
Best regards,
Ole
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