Reinaldo,
like to start with your last comments.
We should recall that an H.248 IP-to-IP MG, - with an H.248
Context with
two H.248 IP Terminations (T1, T2; with Streams S1) -, is
firstly behaving
as an Back-to-Back IP Host (B2BIH), and not as an IP Router
(IPR).
Each H.248 Stream endpoint represents basically an "IP
host" function. The
Stream endpoints within an H.248 Context are interconnected
due to the
"Context Topology". We got an B2BIH.
The second aspect is how IP address/ports of the hosts are
assigned via
H.248 LD & RD. You may see already one gap concerning
the IP SA/SP of the
egress flow.
The B2BIH mode relates to the interconnection of two IP
(bearer) connection
endpoints and correspondingly one or more media flows
(number of H.248
Streams).
The IPR mode has two sub-modes: single H.248 Context for IP
forwarding of
a) single IP connection or
b) multiple connections.
This is then related to the address space (not port space
because it's IP
forwarding, i.e. layer 3 only) behind the H.248
Streams/Terminations. This
requires specific handling of the LD/RD, which could be
controlled via a
new property.
-Albrecht
"Reinaldo Penno"
<rpenno juniper. To:
<Albrecht.Schwarzalcatel-lucent.de>
net> cc:
megacoietf.org
Subject: RE:
H.248 IP Router Package; Re: [Megaco] Question on Interface
Routing ...
28.02.2007 17:53
Wow! You followed up in this? I have to say I'm impressed.
Inline....
> -----Original Message-----
> From: Albrecht.Schwarzalcatel-lucent.de
> [mailto:Albrecht.Schwarzalcatel-lucent.de]
> Sent: Wednesday, February 28, 2007 6:19 AM
> To: Reinaldo Penno
> Cc: megacoietf.org
> Subject: H.248 IP Router Package; Re: [Megaco] Question
on
> Interface Routing ...
>
>
> Reinaldo,
>
> independent of your question concerning the specific
> TerminationID syntax in ES 283 018, we did look at the
IP
> router capability:
>
> > The scenario is a BGF with many input and output
interfaces.
>
> > +----+
> > Ifa -| |-ifx
> > Ifb -| RT |-ify RT means routing table
> > Ibc -| |-ifz
> > +----+
>
> The starting point is an IP-to-IP H.248 Context, and
how the
> "Context" must behave in order to realize an
"IP router"
> function. The requirements for such a functions could
be
> firstly limited to the "IP forwarding
process"
> itself (see e.g. requirements set given by RFC 1812, §
5.2).
>
> When you try to realize such a packet forwarding
process,
> it's fairly obvious that it's not possible to configure
the
> two IP Terminations/Streams via their LDs/RDs and with
> existing H.248 elements for such a behaviour.
Agreed.
> On the other side, introducing e.g. at least two
properties
> (an "IP forwarding" and an "IP FIB"
property), then you may
> achieve a behaviour very close to RFC 1812, § 5.2
IMHO.
>
> ...<snip> (no more details here about such an IP
router
> package because still in discussion ...)
Is there a draft about it?
>
> -Albrecht
>
> PS
> Is there a requirement for such a function in an H.248
MG?
> On the first glance definitely not, because this is
more a
> "call/session-independent function".
Well, I had many discussions about this internally and
externally. Reading
the current specs I told these people that
context/terminations should be
independent of routing, but many (external) people disagree
with me. My
stance is that is fine to disagree as long as there is
something in place
to tell me how a packet should be routed within a context
(and its
ingress/egress terminations).
It could be:
1. Forwarding/routing takes care of it (this would be the
current behavior)
based on the existing specs.
2. Some new package that tells me how to make sure packets
ingress and
egress through the desired interfaces (which at some layer
relate to the
terminations like ip/1/32).
My problem today is that some people want 1 and others 2.
The people that
want 2 believe that a context by definition create some sort
of session
dependent routing. And since the MGC cannot instantiate this
(because it
does see data packets), it tells the MGW to do it. And
creating a context
is a implicit way of doing it.
>From my perspective I just would like this stuff to be
well documented and
specified.
> But we may already support session-independent
functions with
> H.248 ...
>
> Or, an H.248 AGW/TGW or BGW may be interconnected to an
IP
> edge router (ER), thus the MG is a front-end element of
the
> ER. But on the other side you may also embedd the ER
function
> in the MG ... and you may use an H.248 Context for the
ER
> traffic ... etc etc
>
>
>
>
>
>
>
>
>
> Albrecht
>
>
> SCHWARZ/DE/ALCAT To:
> "Reinaldo Penno" <rpennojuniper.net>
>
> ELALCATEL cc:
> megacoietf.org
>
> Subject:
Re:
> [Megaco] Question on Interface Routing in relation to
H.248
> Profile
> 16.10.2006 15:39 for
> controlling Border Gateway Functions (BGF) (ETSI ES 283
018)
>
>
>
>
>
>
>
>
>
> Reinaldo,
>
> 1st H.248 vs IP RIB/FIB
> There aren't any H.248 capabilities defined so far,
allowing the
> modification of IP RIB/FIB data bases. Thus, H.248
is
> entirely decoupled
> from IP routing protocols.
>
> 2nd TerminationID
> Don't over-interprete this TerminatinationID
structure. The defined
> naming convention by ES 283 018 is rather specific
because
> besides the
> basic "identification" function, the
syntax is also a)
> overloaded with
> other functions (a1 -> usage of <group>; a2
-> usage of
> <interface>);
> and b) hierarchical (-> benefit in case of
wildcarding).
>
> The prime purpose behind (a2) is "IP address
realm"
> indication. Please
> note that the ipdc package (H.248.41) was not yet
> available when ES 283
> 018 was defined.
> So, the term "interface" could mislead if
interpreted as
> "IP interface"
> (but this isn't the definition by Table 4/ES 283
018).
>
> - Albrecht
>
>
>
>
> "Reinaldo Penno"
>
> <rpennojuniper. To:
> <megacoietf.org>
>
> net> cc:
>
>
Subject:
> [Megaco] Question
> on Interface Routing in relation to H.248 Profile
for
> 14.10.2006 09:00
controlling
> Border Gateway
> Functions (BGF) (ETSI ES 283 018)
>
>
>
>
>
> In the specification above (or TS 102 333 for that
matter)
> there is a proposal for the termination ID.
>
> "5.6.1.1.1 Overview and prose specification The
Termination
> ID structure shall follow the guidelines of H.248 and
shall
> be based on four fields:
> *
"ip/<group>/<interface>/<id>".&q
uot;
>
> I would like to understand what "interface"
means in this
> context when related to routing.
>
> The scenario is a BGF with many input and output
interfaces.
>
> +----+
> Ifa -| |-ifx
> Ifb -| RT |-ify RT means routing table
> Ibc -| |-ifz
> +----+
>
> Packets come from one of the input interfaces (left),
a
> routing lookup is done, and exit through one of the
output
> interfaces (right).
>
> Given the termination ID ip/1/ifx/200 and a gate with
source
> IP a.b.c.d and destination IP e.f.g.h associated with
it,
> which actions should be done?
>
> A) One should attach the termination to interface Ifx
and if
> packets go through that interface (and termination) any
gate
> actions are applied.
>
> B) One should override the routing table in order to
make
> sure that packets from source a.b.c.d and destination
e.f.g.h
> go through Ifx.
>
>
> The two approaches are quite different:
>
> The first provides a clean separation of Gate Control
and
> routing. You configure routing to make sure the packets
you
> are interested on go through the proper interface (and
> consequently hit the termination) when egress/ingress
the router.
>
> The second approach means an overide of the routing
table by
> the H.248 process. Although possible this represents a
> protocol layer violation and it makes me worried about
> unforseen interaction between routing protocols and
H.248
> driven routing table changes.
>
> What would be the correct interpretation?
>
> Thanks,
>
> Reinaldo
>
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