Re: [netext] Stephen Farrell's Discuss on draft-ietf-netext-pmip-cp-up-separation-05: (with DISCUSS and COMMENT)

["Sri Gundavelli (sgundave)" <[e-mail]>]

HI Stephen,

Please see inline.


On 8/13/14 5:21 AM, "Stephen Farrell" <[e-mail]<mailto:[e-mail]>> wrote:


Hiya,

A few follow ups...

On 09/08/14 17:54, Sri Gundavelli (sgundave) wrote:
Hi Stephen,
Thanks for the review. Please see inline.
On 8/7/14 5:50 AM, "Stephen Farrell" <[e-mail]<mailto:[e-mail]>> wrote:

I have two questions. They could be easy or hard, I'm not
sure:-) Apologies in advance if I've forgotten what little I
ever knew about PMIPv6 and gotten stuff wrong here.
Not at all. Thanks for the discussion.

(1) PMIPv6 traffic between MAG and LMA is generally assumed to
be protected via IPsec, right? Assuming that's actually done,
does figure 1 here indicate a weakening of security since it
shows that IP encapsulation is used between MAG-UP and LMA-UP
without any mention of IPsec. Is that downgrading security? I
get that the binding messages are the most important and will
presumably continue on the control plane but what else changes?
Yes. PMIPv6 allows the use of IPsec security (Tunnel Mode ESP) protection

"allows"? Do you happen to know if that's really used or not
in practice? (That's not a DISCUSS point, but I do wonder.)

Security for user-plane traffic protection is used in very few deployments. Taking the Service Provider Wi-Fi deployment as an example, there is 802.1x security on the air interface, and then there is typical end to end application security (even a Google search is HTTPS protected).  Now requiring security on the user plane traffic between two points in the operator network (LMA and MAG) is some what redundant, IMO. Use of IPsec for UP traffic protection is optional per MIPv6/PMIPv6 specs.  I'd say banking type applications/deployments requires such multi-layer security.



for the user-plane traffic. This is optional and is based on standard
IPsec security. It requires no special interaction between IPsec and the
Proxy Mobile IPv6 entities.
In the split mode (LMA ==> LMA-CP & LMA-DP),

What's LMA-DP? That's not mentioned in the draft? I assume you
mean what the draft calls LMA-UP? (I.e. DP = data plane being
the same as UP = user plane?)

Apologies for the terminology mix up. Yes. LMA-DP (Data Plane) should be the LMA-UP (User Plane)



the MAG (or MAG-DP) and the
LMA-DP can optionally enable IPsec security on the user-plane traffic.

Hmm. So you're saying IPsec can be on for the control plane and
off for the user plane independently? Is that a good plan? I
guess it'd be a bad plan if it were the other way around?


I'd say this is the approach in use for today's integrated LMA (LMA-UP + LMA-CP) based deployments. IPsec security is enabled for CP traffic by default, as it is mandated by PMIPv6 specs. However, the IPsec security for UP is a optional requirement and most deployments don't enable IPsec for UP traffic protection.




MAG-DP establishes a layer-3 p2p tunnel to LMA-DP and both these peers can
be configured to apply IPsec security on the tunneled traffic. So, there
is no loss of functionality here and the CP/DP split approach is not
resulting in weakened security.

Well, it might if IPsec is on for one and off for the other.

Or, if say MAG-CP and MAG-UP are from different vendors, then
I don't know how they signal to one another to turn on/off
IPsec if what we want is for IPsec to be on for both or off
for both.


I'd look at IPsec as a security policy between two peers. Use of IPsec for CP messages between two CP nodes (Ex: MAP-CP and LMA-CP) should not have any bearing on the use/non-use of IPsec security between two UP nodes (Ex: MAG-UP and LMA-UP). The security policy on the two UP nodes strictly determine the use/non-use of IPsec for tunnel traffic protection. But, if the hint is that this policy should be controlled by the respective CP entity, I'd say yes, but that CP to UP interface is out of scope for this work. The controller/CP entity may have a provisioning interface to the UP nodes and that interface may dictate this aspect, but has not implication on this draft.




(2) How does the rest of the Internet know to use the LMA-UP
for the MN and not the LMA-CP? Sorry for being dense but I
don't see how packets from a random Internet node for the MN
end up going down the user plane.
The IP address of the mobile node is topologically anchored on the LMA-DP.

You mean LMA-UP there right?


Yes. Sorry for the terminology mix-up.


>From the point of view of Routing, the LMA-DP owns that larger IP prefix
block from which it allocates to IP prefixes/address to individual
mobility sessions. The LMA-DP is in the path for the user-plane traffic
and is the entry point into the mobile network.  However, the LMA-CP is
only terminating the control signaling from the MAG and is not in the path
for the user-plane traffic.

Is that written down somewhere? If say the LMA-UP and LMA-CP had
utterly different addresses then it couldn't work could it?


This was captured in Section 5.6.2 for IPv6
http://tools.ietf.org/html/rfc5213#page-38

Section 3.1.3 for IPv4
http://tools.ietf.org/html/rfc5844#page-15

When we separate the functionality, the user plane (or the IP address/prefixes allocated to the MN) must be anchored on the LMA-UP. I think we missed capturing this in the spec. Thanks for pointing this out.


OLD:

The LMA Control Plane and the LMA User Plane functions are typically
deployed on the same IP node and in such scenario the interface
between these functions is internal to the implementation.
Deployments may also choose to deploy the LMA Control Plane and the
LMA User Plane functions on seperate IP nodes. In such deployment
models, there needs to be a protocol interface between these two
functions and which is outside the scope of this document. Possible
options for such interface include OpenFlow [OpenFlow-Spec-v1.4.0 <http://tools.ietf.org/html/draft-ietf-netext-pmip-cp-up-separation-06#ref-OpenFlow-Spec-v1.4.0>],
FORCES [RFC5810 <http://tools.ietf.org/html/rfc5810>], use of routing infrastructure
[I-D.matsushima-stateless-uplane-vepc <http://tools.ietf.org/html/draft-ietf-netext-pmip-cp-up-separation-06#ref-I-D.matsushima-stateless-uplane-vepc>] or vendor specific approaches.
This specification does not mandate a specific protocol interface and
views this interface as a generic interface relevant more broadly for
many other protocol systems in addition to Proxy Mobile IPv6.


NEW:

The LMA Control Plane and the LMA User Plane functions are typically
deployed on the same IP node and in such scenario the interface
between these functions is internal to the implementation.
Deployments may also choose to deploy the LMA Control Plane and the
LMA User Plane functions on seperate IP nodes. In such deployment
models, there needs to be a protocol interface between these two
functions and which is outside the scope of this document. Possible
options for such interface include OpenFlow [OpenFlow-Spec-v1.4.0 <http://tools.ietf.org/html/draft-ietf-netext-pmip-cp-up-separation-06#ref-OpenFlow-Spec-v1.4.0>],
FORCES [RFC5810 <http://tools.ietf.org/html/rfc5810>], use of routing infrastructure
[I-D.matsushima-stateless-uplane-vepc <http://tools.ietf.org/html/draft-ietf-netext-pmip-cp-up-separation-06#ref-I-D.matsushima-stateless-uplane-vepc>] or vendor specific approaches.
This specification does not mandate a specific protocol interface and
views this interface as a generic interface relevant more broadly for
many other protocol systems in addition to Proxy Mobile IPv6.
When the LMA Control Plane and the LMA User Plane functions are deployed
on separate IP nodes, the requirement related to user-plane address
anchoring specified in Section 5.6.2 [RFC-5213] and Section 3.1.3 [RFC5844] must
be met by the  node hosting the LMA user plane functionality. The LMA user plane node
must be topological anchor point for the IP address/prefixes allocated
to the mobile node.





----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------


Did you need to say somewhere which PMIPv6 messages are to be
sent in the control plane and which in the user plane? That
might be obvious to some, but its not to me and I guess there
are a bunch of PMIPv6 extensions so I could imagine that
someone somewhere might get it wrong.

The signaling messages {IPv6 with Mobility Header, or IPv4 UDP Port 5436)
traffic is exchanged between MAG-CP and LMA-CP. There is no implication on
the use/non-use of other mobility options.

Sure. My question is: where is it written down which are
signalling messages and which are not?


PMIPv6 Signaling messages (aka control plane messages) are PBU/PBA, BRI/BRA and UPN/UPA messages. The formats for these messages are specified in RFC 5213, 5844, 5846, 5847, 7077.

Ex:
http://tools.ietf.org/html/rfc5213#page-69
http://tools.ietf.org/html/rfc6275#page-42

The identification of any of these CP messages is the use of the following selector.

1. Any IPv4-UDP packets with UDP port 5436
2. Any IPv6 packets with Mobility Header messages

Existing specs clearly explain this and I think its sufficiently clear for the implementors on what traffic goes to LMA-CP and what goes to the LMA-UP.


Regards
Sri




Ta,
S.

The tunneled traffic with L3 encapsulation is between MAG-DP and LMA-DP.
Regards
Sri

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