RE: draft-ietf-v6ops-bb-deployment-scenarios(if DHCP-PD server is not the first router outside of the customer premises??)

["Chip Popoviciu \(cpopovic\)" <cpopovic@cisco.com>]

Hello Tiago,

The document discussed the options available today and points out gaps
that should be further addressed in other work. Solutions to the DHCP-PD
problem are being worked on and snooping is one of them.

Regarding the text comment, I think it is just a matter of context and
terminology. In the context and terminology of the three models
described, the Edge router is the Layer 3 next hop for the customers. In
the LAA model for example there are indeed multiple routers between the
first (access) router and the Edge Router but all of them transport the
customer traffic encapsulated and do not handle it at Layer 3. Despite
all these routers (that are part of the NAP infrastructure), as far as
the customer is concerned, its Layer 3 next hop is the Edge Router.

In the case of a snooping based implementation, only customer's Layer 3
first hop router (be it the IP enabled DSLAM, the BRAS or the ER
depending on the service model) will have to support the snooping
feature. This router has to learn from the snooped DHCP packets what
static routes it should install for the prefixes that were delegated to
the customer connected to it (directly on an interface or virtually over
PPPoE+L2TP for example), the rest of the network will learn from this
router (through the redistribution of the static routes in a IGP) how to
get to the delegated prefixes.

I hope this answers your questions.

Best Regards,
Chip

-----Original Message-----
From: owner-v6ops@ops.ietf.org [mailto:owner-v6ops@ops.ietf.org] On
Behalf Of Tiago Camilo
Sent: Wednesday, July 20, 2005 7:41 AM
To: v6ops@ops.ietf.org
Subject: draft-ietf-v6ops-bb-deployment-scenarios(if DHCP-PD server is
not the first router outside of the customer premises??)

Hi,
I have being following the design of the
draft-ietf-v6ops-bb-deployment-scenarios, and more closely with the
Broadband DSL Networks. And my doubt is concerning the DHCP-PD
functionality in intermediate L3 nodes.
As the author says:

B. Currently the DHCP-PD functionality cannot be implemented if the
DHCP-PD server is not the Edge Router. If the DHCP-PD messages are
relayed, the Edge Router does not have a mechanism to learn the assigned
prefixes and thus install the proper routes to make that prefix
reachable. [...]

Does this issue is already cover, I mean does a new solution rather than
snooping is already proposed?

I also agreed with the comment of Pekka Savola, when he says that:

==> shouldn't you say something like "the first router outside of the
customer premises" instead of Edge Router? (or something a bit more
compact.) 

In a Wholesale IP model, it is possible to have several L3 devices
between the first router outside customer premises and the DHCP server. 
For instance if we consider that the DSLAM is IP enable, than it needs
to be a DHCP-PD relay agent (if the DHCP server is on NSP). My question
is, do we need to implement snooping mechanisms in DSLAM, so that this
device could install the proper routes? What about the following nodes,
the BRAS and the ER, does they need to be also DHCP relay Agents, and
each one with its own snooping mechanism?

 Customer Premise              NAP                    NSP
|---------------| |----------------------| |----------------|
                                                   +-------+
                                                   |  DHCP |
                                              +----+ Server|
                                              |    +-------+
                                              |             |
+----------+    +--------+ +----+-----+ +-----+-----+
|CPE Router+----+ DSLAM  +-+  BRAS    +-+   Edge    |
+----------+    +--------+ +----------+ |  Router   +
                                        +-----------+
                |----------------------------------------|
                                   IP

Thanks,
And best regards,
Tiago Camilo
University of Coimbra