Re: [spring] [Lsr] clarification of locator block and locator node in draft-ietf-spring-srv6-network-programming and draft-ietf-lsr-isis-srv6-extensions

[Peter Psenak <[e-mail]>]

Chris,

please see inline:


On 23/03/2020 17:39, Chris Bowers wrote:
> Peter,
> 
> The proposed SRv6 SID Structure Sub-Sub-TLV has several problems.
> 
> 1) As discussed in item#3 below, it is not clear that flooding LB 
> Length, LN Length, Fun. Length, and Arg. Length to all ISIS speakers is 
> really the right approach.  However, if the WG determines that it is the 
> right approach, the current encodings of this information in the 
> proposed SRv6 SID Structure Sub-Sub-TLV are problematic.  As discussed 
> earlier in this thread, a network operator may choose to not allocate 
> all locators from a single block, so LB Length and LN Length may not be 
> well-defined.  

I'm not sure what do you mean by not "well defined". For every SID you 
need to know the LOC (B+N) part. If you guarantee that it is the same on 
all nodes, you know it from the local config, otherwise, you advertise 
it with a SID.

> The current encoding of the SRv6 SID Structure 
> Sub-Sub-TLV makes it difficult to represent this situation.  The simple 
> thing to do for nodes that don't have a well-defined value of LB Length 
> and LN Length would be to not advertise a value for LB Length and LN 
> Length.  However, since the currently proposed SRv6 SID Structure 
> Sub-Sub-TLV combines LB Length, LN Length, Fun. Length, and Arg. Length 
> into a single sub-sub-TLV, if a node wants to advertise values for Fun. 
> Length and Arg. Length, it also has to advertise values for LB Length 
> and LN Length.  It seems like a better approach would be to have 
> different sub-sub-TLVs, one for  LB Length and LN Length, and a separate 
> one for Fun. Length and Arg. Length to be able to better represent this 
> situation.


I'm afraid you are missing an important point.

SRv6 SID is defined as LOC:FUNCT:ARG, where LOC is represented as B:N. 
To be able to find out where the func and arg are located, you need to 
know the LOC length, e.g. Block and Node length. Advertising just Func 
and Arg length does not help.


> 
> 2) Now consider the situation where a network operator chooses to 
> allocate all locators from a single block, so that LB Length and LN 
> Length are well-defined across the network.  A given node should 
> presumably advertise its own understanding of LB Length and LN Length.   
> A given node's understanding of LB Length and LN Length is a property of 
> the node.  It is not a property of a given End SID.  The currently 
> proposed SRv6 SID Structure Sub-Sub-TLV however is carried within each 
> End SID Sub-TLV.  With the currently proposed encoding, presumably an 
> implementation is expected to send the exact same values of LB Length 
> and LN Length for all of the End SIDs that it advertises.  Not only is 
> this inefficient, but it creates the need for logic to decide what to do 
> when different End SIDs advertised by the same node carry different 
> values of LB Length and LN Length in their sub-sub-TLVs.  It seems like 
> a better approach would be for a given node to advertise its 
> understanding of the value of LB Length and LN Length in a sub-TLV of 
> the Router Capability TLV.

When we design the encoding, we have to define it such, that it supports 
all possible use cases. We can not design the encoding that works for 
single use case (allocate all locators from a single block) and does not 
work for others - different block from different node, multiple blocks 
on a single node (e.g. border node), which are all valid.

> 
> 3) At this point, the only use case that has been proposed for flooding 
> the LB Length, LN Length, Fun. Length, and Arg. Length to all ISIS 
> speakers is to make it more convenient for BGP-LS to get those values to 
> an external controller as part of a topology feed from any ISIS node.  
> No use case has been proposed for ISIS speakers themselves to make use 
> of the information.  It seems like a more scalable approach would be to 
> use BGP-LS sessions to collect the information from the subset of nodes 
> that actually produce the relevant information.  So far there are no End 
> SIDs defined that are advertised in ISIS that have a non-zero Arg. 
> Length.  If an End SID with non-zero Arg. Length were to be proposed in 
> the future as needing to be flooded to all ISIS nodes, it seems likely 
> that the new End SID would also be advertised using the BGP IP/VPN/EVPN 
> control plane.   So it seems like a viable alternative for this 
> hypothetical future End SID would be to have the subset of nodes that 
> have non-zero Arg. Length values communicate to an external controller 
> via  BGP sessions. I think the WG needs a more detailed discussion of a 
> concrete use case in order to determine whether flooding LB Length, LN 
> Length, Fun. Length, and Arg. Length to all ISIS speakers is really the 
> right approach.

there are networks, where BGP is not deployed on all nodes, only on a 
few nodes that re-distribute the information to BGP-LS. In such case we 
need the IGP to distribute this data.

Argument that "it seems likely that the new End SID would also be 
advertised using the BGP IP/VPN/EVPN" is a wishful thinking that we can 
not based our encoding on.


> 
> Given the lack of a compelling use case for flooding LB Length, LN 
> Length, Fun. Length, and Arg. Length to all ISIS speakers and the 
> problems with the currently proposed encodings for doing that, I think 
> that the SRv6 SID Structure Sub-Sub-TLV should be removed from 
> draft-ietf-lsr-isis-srv6-extensions. A mechanism for flooding LB Length, 
> LN Length, Fun. Length, and Arg. Length to all ISIS speakers can be 
> defined in a future document.

The security use case has already been pointed out earlier in this thread:

https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26#section-5

Given the arguments I mentioned above, I respectfully disagree with the 
removal of the SID Structure Sub-Sub-TLV from the ISIS SRv6 draft.

thanks,
Peter


> 
> Thanks,
> Chris
> 
> On Fri, Mar 13, 2020 at 5:02 AM Peter Psenak <[e-mail] 
> <mailto:[e-mail]>> wrote:
> 
>     Hi Chris,
> 
>     On 12/03/2020 15:58, Chris Bowers wrote:
>      > Peter,
>      >
>      > I think that the SRv6 SID Structure Sub-Sub-TLV should be removed
>     from
>      > draft-ietf-lsr-isis-srv6-extensions.  I think that we should
>     leave the
>      > ability to include sub-sub-TLVs in the SRv6 End SID Sub-TLV,
>     End.X SID
>      > Sub-TLV, and LAN End.X SID Sub-TLV in the encodings for those
>     sub-TLVs.
>      >
>      > I don't think that the current text describing the SRv6 SID
>     Structure
>      > Sub-Sub-TLV would result in interoperable implementations.  Based
>     on the
> 
>     SRv6 base spec defines SID B, L, A, F.
> 
>     SRv6 protocol specs are advertising these values with the SRv6 SID,
>     they
>     don't use them. The usage is outside of the scope of the protocol
>     drafts. What exactly is the problem?
> 
>     thanks,
>     Peter
> 
> 
>      > discussion with Ketan below, it appears that use cases for ISIS
>     speakers
>      > receiving advertised values of LB Length, LN Length, Fun. Length,
>     and
>      > Arg. Length are not currently well-defined.    So I think it
>     makes sense
>      > to defer the definition of the SRv6 SID Structure Sub-Sub-TLV to a
>      > future document.
>      >
>      > Thanks,
>      > Chris
>      >
>      > On Thu, Mar 12, 2020 at 6:02 AM Ketan Talaulikar (ketant)
>      > <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>> wrote:
>      >
>      >     Hi Chris,____
>      >
>      >     __ __
>      >
>      >     Dropping the draft-ietf-spring-srv6-network-programming authors
>      >     since we are now back to discussing the ISIS extensions.____
>      >
>      >     __ __
>      >
>      >     Please check inline below.____
>      >
>      >     __ __
>      >
>      >     *From:*Chris Bowers <[e-mail]
>     <mailto:[e-mail]>
>      >     <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >     *Sent:* 05 March 2020 21:53
>      >     *To:* Ketan Talaulikar (ketant) <[e-mail]
>     <mailto:[e-mail]>
>      >     <mailto:[e-mail] <mailto:[e-mail]>>>
>      >     *Cc:* Ketan Talaulikar (ketant) <[e-mail]
>     <mailto:[e-mail]>
>      >     <mailto:[e-mail] <mailto:[e-mail]>>>;
>     [e-mail] <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>;
>      >     SPRING WG List <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>>;
>      >     draft-ietf-spring-srv6-network-programming
>      >     <[e-mail]
>     <mailto:[e-mail]>
>      >     <mailto:[e-mail]
>     <mailto:[e-mail]>>>; Peter
>      >     Psenak (ppsenak) <[e-mail]
>     <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>;
>      >     Bruno Decraene <[e-mail]
>     <mailto:[e-mail]>
>      >     <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >     *Subject:* Re: [Lsr] clarification of locator block and
>     locator node
>      >     in draft-ietf-spring-srv6-network-programming and
>      >     draft-ietf-lsr-isis-srv6-extensions____
>      >
>      >     __ __
>      >
>      >     Ketan,____
>      >
>      >     __ __
>      >
>      >     See inline [CB].____
>      >
>      >     __ __
>      >
>      >     On Wed, Mar 4, 2020 at 12:36 AM Ketan Talaulikar (ketant)
>      >     <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>> wrote:____
>      >
>      >         Hi Chris,____
>      >
>      >         ____
>      >
>      >         You are right in that there is no assumption that all SRv6
>      >         locators in a domain are allocated from the same block.
>      >         Therefore knowing the blocks used in the domain is
>     useful.____
>      >
>      >     ____
>      >
>      >     [CB] Since you refer to "blocks" (plural) in this sentence,
>     are you
>      >     saying that in the scenario where all SRv6 locators in a
>     domain are
>      >     not allocated from the same block, you would expect different
>      >     routers in the same domain to advertise different values of B
>     and N?
>      >     ____
>      >
>      >     */[KT] While personally I believe it would not be the usual
>     case, it
>      >     is left to the operator.____/*
>      >
>      >     */__ __/*
>      >
>      >     For example, assume we have a network where all SRv6 locators
>     in a
>      >     domain are not allocated from the same block.  Router A
>     advertises
>      >     an SRv6 Locator TLV with locator = 2000::/64, and an SRv6 End SID
>      >     sub-TLV with some endpoint behavior. Router B advertises an SRv6
>      >     Locator TLV with locator = 3000::/64, and an SRv6 End SID sub-TLV
>      >     with some endpoint behavior. What should routers A and B
>     advertise
>      >     as the values of B and N in their SRv6 SID Structure
>     Sub-Sub-TLVs ?____
>      >
>      >     */[KT] It is difficult for me to figure out what the block
>     and node
>      >     parts are with such an addressing./*____
>      >
>      >     ____
>      >
>      >         ____
>      >
>      >         The IGP drafts covers the advertisement of the B and N
>     parts of
>      >         the locally configured locator on the node via IGPs. On the
>      >         receiver side, the IGP may not really do much with this
>      >         information, however it enables propagation of this
>     information
>      >         from all nodes in the network to be advertised out via BGP-LS
>      >         (or other mechanisms) as part of the topology feed. Once
>     this is
>      >         part of the topology feed, it enables use-cases on
>     controllers
>      >         to perform network wide validation of the SRv6 SID block
>      >         provisioning and can also help in automation of the security
>      >         aspects described in
>      >
>     https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26#section-5____
>      >
>      >         ____
>      >
>      >     [CB] If an ISIS speaker is not expected to do anything with B
>     and N,
>      >     then I think the text in draft-ietf-lsr-isis-srv6-extensions
>     needs
>      >     to clarify this.  I have a similar observation about Fun.
>     Length and
>      >     Arg. Length in the SRv6 SID Structure Sub-Sub-TLV .  As far
>     as I can
>      >     tell, none of the endpoint behaviors that are currently
>     specified to
>      >     be carried in ISIS End, End.X, and LAN End.X SIDs sub-TLVs
>     uses an
>      >     Argument, so there is never a case where an SRv6 SID Structure
>      >     Sub-Sub-TLV should have a non-zero value for Arg. Length. What
>      >     should an ISIS speaker do if it receives a non-zero value of the
>      >     Arg. Length for an endpoint behavior that doesn't use an
>     argument?
>      >     Are there any use cases envisioned where an ISIS speaker needs to
>      >     know the Arg. Length ? ____
>      >
>      >     */[KT] The behaviors currently listed in the draft do not have an
>      >     argument nor is the use of B and N required for them. We cannot
>      >     preclude a future use-case or extension where such behaviors
>      >     introduced are also applicable to ISIS. So IMHO ruling such
>     aspects
>      >     out might not be the right thing to do from a protocol
>     extensibility
>      >     perspective.____/*
>      >
>      >     */__ __/*
>      >
>      >     */Thanks,____/*
>      >
>      >     */Ketan/*____
>      >
>      >     __ __
>      >
>      >         Thanks,____
>      >
>      >         Ketan____
>      >
>      >         ____
>      >
>      >         *From:*Chris Bowers <[e-mail]
>     <mailto:[e-mail]>
>      >         <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >         *Sent:* 02 March 2020 23:39
>      >         *To:* Ketan Talaulikar (ketant) <[e-mail]
>     <mailto:[e-mail]>
>      >         <mailto:[e-mail] <mailto:[e-mail]>>>
>      >         *Cc:* Ketan Talaulikar (ketant)
>      >         <ketant=[e-mail]
>     <mailto:[e-mail]>
>      >         <mailto:[e-mail]
>     <mailto:[e-mail]>>>; [e-mail]
>     <mailto:[e-mail]>
>      >         <mailto:[e-mail] <mailto:[e-mail]>>; SPRING WG
>     List <[e-mail] <mailto:[e-mail]>
>      >         <mailto:[e-mail] <mailto:[e-mail]>>>;
>      >         draft-ietf-spring-srv6-network-programming
>      >         <[e-mail]
>     <mailto:[e-mail]>
>      >       
>       <mailto:[e-mail]
>     <mailto:[e-mail]>>>;
>      >         Peter Psenak (ppsenak) <[e-mail]
>     <mailto:[e-mail]>
>      >         <mailto:[e-mail] <mailto:[e-mail]>>>;
>     Bruno Decraene
>      >         <[e-mail]
>     <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>>
>      >         *Subject:* Re: [Lsr] clarification of locator block and
>     locator
>      >         node in draft-ietf-spring-srv6-network-programming and
>      >         draft-ietf-lsr-isis-srv6-extensions____
>      >
>      >         ____
>      >
>      >         Ketan,____
>      >
>      >         ____
>      >
>      >         Based on current documents, allocating all SRv6 locators
>     used in
>      >         a domain from a single block is optional.____
>      >
>      >         ____
>      >
>      >         However, assuming for the moment that a network operator has
>      >         chosen to allocate all SRv6 locators used in a domain from a
>      >         single block, so that there is a well-defined value of B
>     and N
>      >         across a domain, what is the use of having a router advertise
>      >         its own understanding of these two values?  And what is a
>      >         receiver supposed to do with this information?____
>      >
>      >         ____
>      >
>      >         Thanks,____
>      >
>      >         Chris____
>      >
>      >         ____
>      >
>      >         On Fri, Feb 28, 2020 at 8:23 AM
>     <[e-mail] <mailto:[e-mail]>
>      >         <mailto:[e-mail]
>     <mailto:[e-mail]>>> wrote:____
>      >
>      >             Hi Ketan,____
>      >
>      >             ____
>      >
>      >             Thanks fort the follow up.____
>      >
>      >             Clarification inline [Bruno]____
>      >
>      >             ____
>      >
>      >             *From**:*Ketan Talaulikar (ketant)
>     [mailto:[e-mail] <mailto:[e-mail]>
>      >             <mailto:[e-mail] <mailto:[e-mail]>>]
>      >             *Sent:* Friday, February 28, 2020 11:11 AM
>      >             *To:* DECRAENE Bruno TGI/OLN; Ketan Talaulikar (ketant);
>      >             Chris Bowers
>      >             *Cc:* [e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; SPRING WG List;
>      >             draft-ietf-spring-srv6-network-programming; Peter Psenak
>      >             (ppsenak)
>      >             *Subject:* RE: [Lsr] clarification of locator block and
>      >             locator node in
>     draft-ietf-spring-srv6-network-programming
>      >             and draft-ietf-lsr-isis-srv6-extensions____
>      >
>      >             ____
>      >
>      >             Hi Bruno,____
>      >
>      >             ____
>      >
>      >             I believe the description and usage of Locator is
>     very well
>      >             described and covered in the net-pgm draft as also the
>      >             corresponding IGP extensions. Is the question is more
>     about
>      >             the “block” part of it (what is not in the block part
>     is in
>      >             the node part as per the text in the net-pgm draft)?____
>      >
>      >             ____
>      >
>      >             The “block” is again not a new thing. Please check the
>      >             following:____
>      >
>      >             Under
>      >
>     https://tools.ietf.org/html/draft-ietf-6man-segment-routing-header-26#section-5
>      >             … look for “block”____
>      >
>      > https://tools.ietf.org/html/rfc8402#section-2 … look under
>      >             SRGB for SRv6____
>      >
>      >             ____
>      >
>      >             [Bruno]____
>      >
>      >             To clarify, my question was not specific to “block” but
>      >             related to the usage, by the receiver, of the following
>      >             piece of information:____
>      >
>      >             ____
>      >
>      >                    LB Length: SRv6 SID Locator Block length____
>      >
>      >                    LN Length: SRv6 SID Locator Node length____
>      >
>      >                    Fun. Length: SRv6 SID Function length____
>      >
>      >                    Arg. Length: SRv6 SID Arguments length____
>      >
>      >             ____
>      >
>      >             ____
>      >
>      >             So perhaps I don’t get Chris’s point and would wait
>     for him
>      >             to clarify.____
>      >
>      >             [Bruno] I’ll leave this to Chris.____
>      >
>      >             ____
>      >
>      >             Thanks,____
>      >
>      >             Ketan____
>      >
>      >             ____
>      >
>      >             *From:*Lsr <[e-mail]
>     <mailto:[e-mail]>
>      >             <mailto:[e-mail]
>     <mailto:[e-mail]>>> *On Behalf Of
>      >             *[e-mail]
>     <mailto:[e-mail]> <mailto:[e-mail]
>     <mailto:[e-mail]>>
>      >             *Sent:* 28 February 2020 14:34
>      >             *To:* Ketan Talaulikar (ketant)
>      >             <ketant=[e-mail]
>     <mailto:[e-mail]>
>      >             <mailto:[e-mail]
>     <mailto:[e-mail]>>>; Chris Bowers
>      >             <[e-mail]
>     <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>>
>      >             *Cc:* [e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; SPRING WG List
>      >             <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>>;
>      >             draft-ietf-spring-srv6-network-programming
>      >             <[e-mail]
>     <mailto:[e-mail]>
>      >           
>       <mailto:[e-mail]
>     <mailto:[e-mail]>>>;
>      >             Peter Psenak (ppsenak) <[e-mail]
>     <mailto:[e-mail]>
>      >             <mailto:[e-mail] <mailto:[e-mail]>>>
>      >             *Subject:* Re: [Lsr] clarification of locator block and
>      >             locator node in
>     draft-ietf-spring-srv6-network-programming
>      >             and draft-ietf-lsr-isis-srv6-extensions____
>      >
>      >             ____
>      >
>      >             Hi Ketan,____
>      >
>      >             ____
>      >
>      >             ____
>      >
>      >             ____
>      >
>      >             *From:*Lsr [mailto:[e-mail]
>     <mailto:[e-mail]>] *On Behalf Of
>      >             *Ketan Talaulikar (ketant)
>      >             *Sent:* Friday, February 28, 2020 6:30 AM____
>      >
>      >             ____
>      >
>      >             Hi Chris,____
>      >
>      >             ____
>      >
>      >             I agree with Peter and I would suggest to drop LSR since
>      >             this is not a protocol specific thing.____
>      >
>      >             ____
>      >
>      >             I believe the text in
>      >             draft-ietf-spring-srv6-network-programming clears
>     says what
>      >             locator block and locator node are. What more details
>     do you
>      >             think are required?____
>      >
>      >             ____
>      >
>      >             [Bruno] Speaking as an individual, the draft could
>     possibly
>      >             clarify the usage of these information/fields by the
>      >             receiver. Possibly using the same name/term (e.g.
>     SRv6 SID
>      >             Locator Block length) to ease the references between both
>      >             drafts.____
>      >
>      >             ____
>      >
>      >             Thanks,____
>      >
>      >             --Bruno____
>      >
>      >             ____
>      >
>      >             Thanks,____
>      >
>      >             Ketan____
>      >
>      >             ____
>      >
>      >             *From:*Lsr <[e-mail]
>     <mailto:[e-mail]>
>      >             <mailto:[e-mail]
>     <mailto:[e-mail]>>> *On Behalf Of *Chris Bowers
>      >             *Sent:* 27 February 2020 22:46
>      >             *To:* [e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>; SPRING WG List
>      >             <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>>
>      >             *Cc:* Peter Psenak (ppsenak) <[e-mail]
>     <mailto:[e-mail]>
>      >             <mailto:[e-mail] <mailto:[e-mail]>>>
>      >             *Subject:* [Lsr] clarification of locator block and
>     locator
>      >             node in draft-ietf-spring-srv6-network-programming and
>      >             draft-ietf-lsr-isis-srv6-extensions____
>      >
>      >             ____
>      >
>      >             SPRING and LSR WGs,____
>      >
>      >             ____
>      >
>      >             I think that we need a much more detailed description
>     of the
>      >             locator block and locator node in either
>      >             draft-ietf-spring-srv6-network-programming or
>      >             draft-ietf-lsr-isis-srv6-extensions.  See original email
>      >             below.____
>      >
>      >             ____
>      >
>      >             Thanks,____
>      >
>      >             Chris____
>      >
>      >             ____
>      >
>      >             On Thu, Feb 27, 2020 at 11:08 AM Peter Psenak
>      >             <[e-mail] <mailto:[e-mail]>
>     <mailto:[e-mail] <mailto:[e-mail]>>> wrote:____
>      >
>      >                 Hi Chris,
>      >
>      >                 On 27/02/2020 17:54, Chris Bowers wrote:
>      >                  > LSR WG,
>      >                  >
>      >                  > Section 9 of
>     draft-ietf-lsr-isis-srv6-extensions-05
>      >                 defines the  SRv6
>      >                  > SID Structure Sub-Sub-TLV. In particular, it
>     defines
>      >                 encoding for the
>      >                  > locator block length and the locator node length.
>      >                 The text refers to
>      >                  > [I-D.ietf-spring-srv6-network-programming] for the
>      >                 definition of these
>      >                  > concepts.
>      >                  >
>      >                  > As far as I can tell, the only reference to
>     locator
>      >                 block and locator
>      >                  > node in
>     draft-ietf-spring-srv6-network-programming-10
>      >                 is section 3.1
>      >                  > which has the following text:
>      >                  >
>      >                  >     A locator may be represented as B:N where B is
>      >                 the SRv6 SID block
>      >                  >     (IPv6 subnet allocated for SRv6 SIDs by the
>      >                 operator) and N is the
>      >                  >     identifier of the parent node
>     instantiating the
>      >                 SID...
>      >                  >
>      >                  > I think that we need a much more detailed
>     description
>      >                 of the locator
>      >                  > block and locator node.
>      >
>      >                 sure, but that would be in the
>      >                 draft-ietf-spring-srv6-network-programming-10, not in
>      >                 draft-ietf-lsr-isis-srv6-extensions, as these are
>     not a
>      >                 protocol
>      >                 specific constructs.
>      >
>      >                 thanks,
>      >                 Peter
>      >
>      >                  >
>      >                  > Thanks,
>      >                  >
>      >                  > Chris
>      >                  > ____
>      >
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