Subject: [PWE3] Multiple RSVP paths

From: Stewart Bryant <[email-masked]>
Date: Mon, 05 Jul 2010 15:07:21 +0100

In response to a comment received during last call I have added a new 
section 7.3 entitled : "Multiple RSVP-TE Paths" which says:

In some networks it is desirable for a Label Edge Router (LER) to be 
able to load balance a PW across multiple RSVP-TE tunnels. The flow 
label mechanism described in this document may be used to provide the 
LER with the required flow information, and necessary entropy to provide 
this type of load balancing. Methods by which the LER is configured to 
apply this type of ECMP is outside the scope of this document.

- Stewart

---

From: Curtis Villamizar <[email-masked]>
Date: Tue, 06 Jul 2010 11:30:04 -0400

In message <[email-masked]>
> apply this type of ECMP is outside the scope of this document.

Stewart,

You could mention using a link bundle with the all ones component
link as a possibility but still leave further details out of scope and
not preclude other mechanisms that are local to the LER.

Curtis

---

From: Stewart Bryant <[email-masked]>
Date: Tue, 06 Jul 2010 16:45:06 +0100

On 06/07/2010 16:30, Curtis Villamizar wrote:
> In message<[email-masked]>
> Stewart Bryant writes:
>    
>>

Curtis

The draft contains the following text (from the previous version)

=========

7.2.  Link Aggregation Groups

    A Link Aggregation Group (LAG) is used to bond together several
    physical circuits between two adjacent nodes so they appear to
    higher-layer protocols as a single, higher bandwidth "virtual" pipe.
    These may co-exist in various parts of a given network.  An advantage
    of LAGs is that they reduce the number of routing and signalling
    protocol adjacencies between devices, reducing control plane
    processing overhead.  As with ECMP, the key problem related to LAGs
    is that due to inefficiencies in LAG load-distribution algorithms, a
    particular component of a LAG may experience congestion.  The
    mechanism proposed here may be able to assist in producing a more
    uniform flow distribution.

    The same considerations requiring a flow to go over a single member
    of an ECMP path set apply to a member of a LAG.

==========

Does this cover your issue? If not, then please can you help with some text.

I do not understand what you mean by "link bundle with the all ones component
link"

- Stewart

---

From: Greg Mirsky <[email-masked]>
Date: Tue, 6 Jul 2010 09:04:29 -0700

Dear Stewart, Curtis and All,
I believe that "all ones" refers to the scenario when a label is valid
across all component links of the given bundled link (Section 2.3.
paragraph before the last of the section).

Regards,
Greg

On Tue, Jul 6, 2010 at 8:45 AM, Stewart Bryant <[email-masked]> wrote:
> _______________________________________________
> pwe3 mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/pwe3
>

---

From: John E Drake <[email-masked]>
Date: Tue, 6 Jul 2010 09:10:35 -0700

Hi,

A related ID:

http://www.ietf.org/id/draft-kompella-mpls-rsvp-ecmp-00.txt

Thanks,

John
> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On Behalf Of
> Curtis Villamizar
> Sent: Tuesday, July 06, 2010 8:30 AM
> To: [email-masked]
> Cc: [email-masked]; pwe3
> Subject: Re: [PWE3] Multiple RSVP paths
> 
>

---

From: Curtis Villamizar <[email-masked]>
Date: Tue, 06 Jul 2010 13:49:40 -0400

> paragraph before the last of the section).

Greg,

Yes.  RFC 4201 section 2.3.  If the component links are LSP then the
load split can be done proportional to the bandwidth reserved for the
LSP, giving the operator fine control over the load balance, if the
implementation can handle this.

This eliminates the down side that is referred to in the LAG section.

Many PW may be carried over a set of LSP that are concatonated as a
link bundle.  This use of fat-pw and link bundle allows better
statistical multiplexing of PW than statically allocation PW to the
component LSP.

Using LAG over LSP would require adding an extra layer of Ethernet MAC
that serves no purpose.  It could be done by using PW over LSP over
LAG over Ethernet PW but that is ugly.

Curtis

---

From: Greg Mirsky <[email-masked]>
Date: Tue, 6 Jul 2010 10:57:23 -0700

Dear Curtis,
I remember that I was pointed to this scenario as I've overlooked the
possibility to use link bundle with load balancing.

Regards,
Greg

---

From: Curtis Villamizar <[email-masked]>
Date: Tue, 06 Jul 2010 14:12:15 -0400

> http://www.ietf.org/id/draft-kompella-mpls-rsvp-ecmp-00.txt

John,

The use of the E-bit is not clear.  If the sub-LSP all have E=0, is
the load split proportional to the sub-LSP reserved bandwidth?  If E=1
are the reserved bandwidths of the component LSP all ignored?  What
happens if E=0 for some sub-LSP and E=1 for others?

Also in the figure:

                          ------------- M -----
                         /                      \
                        /           --- P --     \
                       /           /         \    \
                      A --- X --- Y --- Q --- T --- B
                             \     \              / |
                              \     --- R -------   |
                               \                    |
                                ------- S ----------

It is possible to set up link bundle Y-P-T and Y-Q-T as Y-T at PSC-4,
then bundle Y-P-T-B and Y-R-B as Y-B at PSC-3, then X-Y-B and X-S-B as
X-B at PSC-2, and A-M-B and A-X-B as A-B as PSC-1.  Done with one PSC
value to spare (the implied PSC=0).

This use of link bundling would yield the finest control over the
allocation of resources.  Each link bundle is the sum of the
components.

The problem with link bundling and a limitation of the draft in
question is that some LSP over this bundled LSP cannot specify that it
*needs* to take one component (to be MPLS-TP compliant, for example),
and allow other LSP to indicate that it is fine to load split it.

[  And now a word for our sponsor.  :-)  ]
See draft-villamizar-mpls-tp-multipath-00 for further requirements.

Curtis

---

From: John E Drake <[email-masked]>
Date: Tue, 6 Jul 2010 12:14:19 -0700

Stewart,

Link bundling (http://datatracker.ietf.org/doc/rfc4201/) is very different from LAGs.

Thanks,

John

> Stewart Bryant
> Sent: Tuesday, July 06, 2010 8:45 AM
> To: [email-masked]

---

From: Yong Lucy <[email-masked]>
Date: Thu, 08 Jul 2010 17:15:08 -0500

Hi John,

It is not clear to me 

1) how the proposed solution works in Figure 1 situation of the draft. Even
the receiver B assigns the same label for all five sub-LSPs, because there
are intermediate nodes between A and B, the sender A will be asked to use
the different labels for five sub-LSPs, is that right?  

2) For the following MLSP case, do sub-LSPs start from node A or from node
W?

                           --L--   --P-- 
                          /     \ /     \
                  A------W       S---Q---B
                          \     / \     /
                           --M--   --R-- 

Thanks,
Lucy

> From: [email-masked] [mailto:[email-masked]] On Behalf Of
> John E Drake
> Sent: Tuesday, July 06, 2010 11:11 AM
> To: [email-masked]; [email-masked]
> Cc: [email-masked]; [email-masked]; pwe3
> Subject: Re: [mpls] [PWE3] Multiple RSVP paths
> 
> Hi,
> 
> A related ID:
> 
> mpls mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mpls

---

From: Stewart Bryant <[email-masked]>
Date: Fri, 09 Jul 2010 11:27:32 +0100

> not preclude other mechanisms that are local to the LER.
The text now says:

7.3.  Multiple RSVP-TE Paths

    In some networks it is desirable for a Label Edge Router (LER) to be
    able to load balance a PW across multiple RSVP-TE tunnels.  The flow
    label mechanism described in this document may be used to provide the
    LER with the required flow information, and necessary entropy to
    provide this type of load balancing.  An example of such a case is
    the of the flow label mechanism in networks using a link bundle with
    the all ones component [RFC4201].

    Methods by which the LER is configured to apply this type of ECMP is
    outside the scope of this document.

Hopefully this is OK.

I am going to upload the document and request a last call. If the text is still not correct, then please supply some new text and we will address as a last call comment.

- Stewart