I really didn't expect this argument. These are not use cases; they are
the procedures necessary to calculate the bits that go on the wire due
to the complexity of the MAP formulation. Take a look at the code being
implemented in your routers and you will see similar branches in logic
or variations on them. What would go into a deployment document would be
how to apply these different formulations to particular network situations.
Tom
On 25/02/2013 4:51 AM, Ole Troan wrote:
Tom, et, al,
thanks for the suggestion. I would lean towards pushing back on rewriting
section 5, on the grounds
that this is a set of generic tools and that specific use cases rather could go
in a deployment document.
does anyone else have strong opinions on current text versus Tom's proposed
changes?
cheers,
Ole
On Feb 21, 2013, at 16:43 , Tom Taylor <[email protected]> wrote:
The two bullets below were actually a "Trojan Horse" of sorts. They set the
agenda for Sections 5.2 and 5.3 respectively. I think those two sections should have
different titles to start with:
5.2 Provisioning the MAP IPv4 Address, MAP IPv6 Address, and Port Set
Identifier (PSID) At a CE
5.2.1 Deriving the IPv4 Address and PSID From the End-User IPv6 Prefix and the
Basic Mapping Rule
5.2.2 Deriving the IPv6 Address To Use On the MAP Interface
5.3 Deriving the MAP IPv6 Address From the IPv4 Address and Port and the
Matching Forwarding Mapping Rule (Mesh Mode Only)
The procedure described in each section should then match the title. I'll
sketch the flow here, but I can supply detailed text if desired.
5.2.1 Deriving the IPv4 Address and PSID From the End-User IPv6 Prefix and the
Basic Mapping Rule
- distinguishing the Basic Mapping Rule (BMR) from other mapping rules that are
provisioned
- locating the Extended Address (EA) bits in the End-User IPv6 Prefix
- Case 1: Port set identifier (PSID) is explicitly provisioned separately from
the BMR
-- IPv4 address is shared
-- IPv4 address is the concatenation of the IPv4 prefix provided in the BMR and
the IPv4 suffix provided by the EA bits
-- if the result is not a /32, error
- Case 2: PSID is embedded in the EA bits
-- true if the sum (o + r) is greater than 32, where o is the number of EA bits
as indicated by the BMR, and r is the length of the IPv4 prefix supplied by the
BMR
-- shared IPv4 address is the concatenation of the IPv4 prefix supplied by the
BMR and as many of the high-order bits within the EA bit field as required to
make up a /32
-- PSID is given by the remaining lower-order bits in the EA bit field
- Case 3: non-shared IPv4 address or prefix
-- true if the sum (o + r) as defined above is less than or equal to 32
-- IPv4 address or prefix is equal to the concatenation of the IPv4 prefix as
supplied by the BMR with the entire contents of the EA bit field.
5.2.2 Deriving the IPv6 Address To Use On the MAP Interface
- MAP IPv6 address is given by the concatenation of the provisioned End-User
IPv6 Prefix with an interface identifier derived as described in Section 6.
- this applies for both hub-and-spoke and mesh mode
5.3 Deriving the MAP IPv6 Address From the Destination IPv4 Address and Port
and the Matching Forwarding Mapping Rule (Mesh Mode Only)
- locate the applicable Mapping Rule by longest match on rule IPv4
address/prefix
- Derive the target End-User IPv6 prefix less the subnet identifier as follows:
-- Case 1: length of the EA field as given by the selected Mapping Rule is 0
--- target End-User IPv6 prefix (less the subnet identifier) is equal to the
IPv6 prefix provided by the selected Mapping Rule
-- Case 2: sum (o + r) is less than or equal to 32, where o and r are as
defined in Section 5.2
--- implies destination IPv4 address/prefix is dedicated to destination CE
--- EA bit field is equal to the highest-order o bits of the destination IPv4
address not contained in the IPv4 address/prefix provided by the selected
Mapping Rule
--- target End-User IPv6 prefix (less the subnet identifier) is equal to the
IPv6 prefix provided by the selected Mapping Rule followed in concatenation
with the derived EA bit field
-- Case 3: sum (o + r) as defined above is greater than 32
--- implies destination IPv4 address/prefix is shared
--- set the high-order portion of the EA bit field equal to the low-order (32 -
r) bits of the destination IPv4 address
--- the remaining o - (32 - r) bits of the EA bit field are equal to the
high-order bits of the destination port number, beginning with the bit after
the offset given by the selected Mapping Rule (default = 6)
--- target End-User IPv6 prefix (less the subnet identifier) is equal to the
IPv6 prefix provided by the selected Mapping Rule followed in concatenation
with the derived EA bit field
- subnet identifier portion of the End-User IPv6 prefix is all zeroes
- End-User MAP Address is equal to the End-User IPv6 prefix concatenated with
an interface identifier (IID) derived as described in Section 6.
Tom Taylor
On 13/02/2013 3:07 AM, Ole Troan wrote:
I agree with Tom's proposed changes.
I'll put them in a upcoming revision 05, if no-one objects.
(I still think we can do a WGLC on revision 04).
cheers,
Ole
Remark: I'm not sure the two bullets (quoted further down) tell the full story
as they stand. I propose to modify them as follows:
1. Basic Mapping Rule (BMR) - mandatory. There can only be one
Basic Mapping Rule per End-user IPv6 prefix. In combination
with the End-user IPv6 prefix, the Basic Mapping Rule is used
to derive the IPv4 prefix, address, or shared address and
the PSID assigned to the CE.
2. Forwarding Mapping Rule (FMR) - optional, used for forwarding.
The Basic Mapping Rule is also a Forwarding Mapping Rule. Each
Forwarding Mapping Rule will result in an entry in the Rules
table for the Rule IPv4 prefix. Given a destination IPv4 address
and port within the MAP domain, a MAP node can use the matching
FMR to derive the End-user IPv6 address of the interface through
which that destination address-port combination can be reached.
On 12/02/2013 9:22 AM, Ole Troan wrote:
Tom,
Thanks. What about the assertions in the bullets?
sorry, may be my short term memory... what do you mean?
cheers,
Ole
On 12/02/2013 3:27 AM, Ole Troan wrote:
Tom,
I'm still hoping to see a response to this.
On 06/02/2013 8:42 AM, Tom Taylor wrote:
Section 5 of the latest version of MAP has the following:
1. Basic Mapping Rule (BMR) - mandatory, used for IPv4 prefix,
address or port set assignment. There can only be one Basic
Mapping Rule per End-user IPv6 prefix. The Basic Mapping Rule is
used to configure the MAP IPv6 address or prefix.
2. Forwarding Mapping Rule (FMR) - optional, used for forwarding.
The Basic Mapping Rule is also a Forwarding Mapping Rule. Each
Forwarding Mapping Rule will result in an entry in the Rules
table for the Rule IPv4 prefix.
Question: there will always be a BMR. In the absence of additional
rules, how does a CE know whether it can use the BMR for forwarding or
must always use the default rule?
the answer to that is in section 7, last bullet.
that is, the MAP CE must be configured to be in hub and spoke mode or mesh mode.
which mode it is in decided if the BMR is used for forwarding or not.
cheers,
Ole
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