I strongly agree that we need to start collecting the use-cases for multiple abstraction levels as well as physical/virtual/private.
Alia On Aug 3, 2012 4:51 PM, "Y. Richard Yang" <[email protected]> wrote: > Hi Volker, > > On 8/3/12 12:02 PM, Volker Hilt wrote: > >> >> I believe that the capability to provide a simplified view on the network >> topology to an application is a key feature rather than a bug. Applications >> that want to have a view on network topology don't need need a fine grained >> view on the topology in most casts and benefit from having an abstracted >> view. This will simplify processing for the application and enables >> providers to control the exposure of details. >> > Agreed. > > We've seen some numbers for topology data sizes in the incremental >> updates presentation in the ALTO meeting, which provide some insights into >> the amounts of data needed for different topology sizes. >> >> I like the idea of enabling an ALTO server to offer different levels of >> details. This will enable a server to tailor responses to the specific >> client. It will add complexity as the ALTO server itself will have to >> maintain the most complex topology it is offering and will have to keep >> this topology up to date. But this is an interesting question for >> discussion in the WG. >> >> Glad that you also like the idea of different levels of details of the > network topology. If the ALTO Server is given a detailed topology > (constructed from multiple sources, such as routing feed, LSP feed, > configuration files), we can offer multiple topology operators/aggregators > to explore the detailed topology, according to need and policy. A simple > example operator is level (i.e., hierarchy such as at the area level), but > one might specify other operators (e.g., fisheye focus). There are studies > on representation of multi-level graphs that we can try to take advantage > of. This can be a subject for the group to explore. > > We may need to study/collect use cases for multiple level topology. One > interesting example immediately coming to mind is the Abstract Node concept > (specify IP prefix/ASN) used in RSVP-TE. > > Cheers, > > Richard > > Cheers, >> >> Volker >> >> >> >> >> >> >> >> On 03.08.2012 11:03, Y. Richard Yang wrote: >> >>> Hi Stefano, >>> >>> Good post! I added the ALTO mailing list, given the relevance. I hope >>> that this is OK cross posting. >>> >>> First, a few comments on ALTO: >>> >>> View granularity: >>> >>> - ALTO currently defines two abstract network topology data structures: >>> Network Map and Cost Map(s). More link-state oriented maps (graphs), >>> with aggregations and transformations, can be added efficiently to ALTO. >>> Some initial efforts are already on the way (e.g., see the graph >>> representation proposal at page 9: >>> http://www.ietf.org/**proceedings/84/slides/slides-**84-alto-1.pdf<http://www.ietf.org/proceedings/84/slides/slides-84-alto-1.pdf>). >>> Hence, >>> I see a natural next-step is for ALTO to provide a link-state view to >>> external entities. >>> >>> - It is a good comment on the level of details that ALTO should >>> delivery. This is a good question for the ALTO working group and the >>> community to discuss. I feel that ALTO should provide multi-levels of >>> granularity of views, and we should discuss in the working group. >>> >>> Pull vs push delivery mechanism: >>> >>> - There are more discussions on adding the incremental update in ALTO. >>> Multiple mechanisms have been discussed. I feel that it is the right >>> direction for ALTO. >>> >>> Now let me understand the deployment model of BGP-LS. Your explanation >>> on the issues of acquiring routing state is excellent. Let me start by >>> understanding more details on the deployment model of BGP-LS inside a >>> network: >>> >>> - A set N_igp of BGP-LS instances are deployed to collect IGP info. You >>> need multiple instances because IGP needs direct connectivity >>> (adjacency). Each instance here receives (potentially multiple) IGP >>> updates and streams (relays) to an another (remote) entity, which I >>> assume is a master BGP-LS instance. So each of these N_igp instances is >>> IGP-in and BGP-LS out. This appears to be shown in Figure 1 of >>> draft-gredler-idr-ls-**distribution. >>> >>> - A set N_egp of BGP-LS instances are deployed to collect BGP feeds. You >>> also may need multiple instances because the network does not want to >>> see aggregated states but raw states. These instances will feed to the >>> master BGP-LS as well. >>> >>> - The master BGP-LS aggregates the multiple BGP-LS ins (and maybe some >>> direct IGP/EGP ins) and pushes (after policy) to other BGP-LS peers to >>> use: for example, an ALTO Server transforms/aggregates the feed to >>> generate ALTO views (maps and graphs), and an PCE uses the feed to >>> maintain its TED. One could even imagine that ALTO builds a detailed TED >>> and feeds to PCE, but this beyond the scope of this discussion. The >>> master BGP-LS is BGP-LS in and BGP-LS out. It is also possible that the >>> master BGP-LS does not push to any other entities and simply maintains >>> an internal DB for others to query. >>> >>> Do I understand it correctly? >>> >>> Now, we can take a look at more specifics of BGP-LS. >>> >>> A first perspective is the semantics of the content. If the objective is >>> to solve the aforementioned deployment issue, then an alternative >>> solution is to introduce a simple LS update tunneling protocol, where a >>> link-state proxy forwards LS messages to a collector. The current design >>> of BGP-LS starts with such a feeling (i.e., an NLRI starts with the >>> Protocol ID, which indicates it is from IS-IS level 1 IS-IS level 2, >>> OSPF, etc). However, the protocol appears to (try to) go beyond simple >>> tunneling and introduces a common LS schema, by converting/filtering >>> individual IGP LS messages to some common format. I feel that it can be >>> helpful to first specify the schema (LS data model) instead of the >>> specific encoding. For example, OSPF specifies LS Age, and this is >>> filtered. (Please correct me if I missed it). On the other hand, one can >>> think that some Age info can be helpful for one to understand the >>> "freshness" of the LS. A problem studied in database is heterogeneous >>> databases, to merge multiple data sources (IS-IS, OSPF, etc) to a single >>> schema, and there can be many problems. If there is such a study, please >>> do share a pointer. >>> >>> A second perspective is using BGP as the transport. What key features >>> from BGP do we really need (yes, weak-typed TLV encoding offers a lot of >>> flexibility)? What features of BGP do we not need (e.g., BGP is a >>> routing protocol and hence builds in features to handle convergence such >>> as dampening)? What may be missing (e.g., a capability of pull or >>> filtering of push). I feel that these issues should be discussed. If >>> they have already been discussed, please do share a pointer, as I am >>> definitely a new comer. >>> >>> Thanks! >>> >>> Richard >>> >>> On 8/2/12 11:54 PM, stefano previdi wrote: >>> >>>> All, >>>> >>>> as co-author of both BGP-LS and ALTO drafts, I'd try to clarify a few >>>> things: >>>> >>>> ALTO has been designed in order to deliver to applications (through >>>> http/json): >>>> >>>> 1. two maps representing the network topology in an abstracted view >>>> (or set of views through multiple maps). The map does not include >>>> the details of a link-state database and therefore have little use >>>> for any element that would need to retrieve from the network the >>>> detailed/complete network layer topology, for example: link >>>> addresses or link BW resources, etc. IOW: ALTO maps do not have >>>> the granularity of a link-state database and ALTO protocol is not >>>> designed to deliver such details. >>>> >>>> and/or >>>> >>>> 2. Ranking services where a client sends a bunch of IP addresses in >>>> a message and the ALTO server replies by ranking these addresses >>>> based on their topological/network distance (or whatever criteria >>>> the ALTO server has been configured for). This is called: Endpoint >>>> Cost Service. >>>> >>>> When using ALTO maps, and the ALTO protocol being http/pull based, >>>> there's no such concept of unsolicited routing updates. An ALTO >>>> client is typically a browser that will pull the maps from an ALTO >>>> server using http. The ALTO server will make no effort to ensure the >>>> client has the latest view of the topology (i.e.: It's the role of the >>>> client to poll for new maps time to time). >>>> >>>> Now, in order for an ALTO server to deliver Maps or Ranking services, >>>> it needs to build some form of topology and in order to achieve this, >>>> it needs somehow to be fed by either the operator (configuration) or >>>> to receive dynamically topology information from the network (e.g.: >>>> ISIS/OSPF/BGP). >>>> >>>> Here we had two options: >>>> 1. ALTO server to implement ISIS/OSPF/BGP and establish IGP adjacencies >>>> to ABRs or L1L2 routers in each area so to retrieve the LSDB from >>>> each area. In practice I know no SP willing/accepting to open their >>>> IGP to an ALTO server. Also, IGP requires direct connectivity >>>> (adjacency) so from an operation point of view is complex and not >>>> desired. >>>> 2. Use a database distribution protocol running on top of a reliable >>>> transport layer that would allow an ALTO server to connect to a >>>> _single_ and _remote_ Route Reflector (i.e.: no need to be directly >>>> connected) and grab the whole network topology that will be updated >>>> using standard routing protocol mechanisms (i.e.: routing updates) >>>> and that would allow the operator to control (through policies and >>>> filters) what to distribute and to which server. >>>> >>>> Benefits: single (or dual at most for redundancy) connection for >>>> the ALTO server (rather than having a direct adjacency with each >>>> ABR) and, from the operator perspective, single point of >>>> distribution of network topology (easier to apply policies and >>>> control what you deliver). This is what BGP-LS is about. >>>> >>>> BGP-LS defines new AFI/SAFI for a new NLRI and attributes that convey >>>> link-state and, more generically, any type of topology information. >>>> The draft specifies NLRI and attributes that map whatever you can >>>> find in a link-state database. >>>> >>>> We currently have draft-gredler-idr-ls-**distribution in the process >>>> (hopefully) to be adopted as WG item in IDR WG (so far we 're getting >>>> good support). We also have 3 implementations of BGP-LS. >>>> >>>> Deployment-wise: BGP-LS is not yet deployed, however, we already have >>>> deployments (I know at least two) where an ALTO server retrieves IP >>>> prefix information from remote BGP RRs (for ipv4). The same scheme >>>> will be used once BGP-LS will be deployed (so to say that it is not >>>> something that we invented after a couple of beers but corresponds to >>>> requirements for delivering network services to upper layers while >>>> still controlling efficiently what you distribute, to whom and in >>>> which form (note that, often, beers are anyway part of the process). >>>> >>>> More information here: >>>> http://tools.ietf.org/html/**draft-gredler-idr-ls-**distribution-02<http://tools.ietf.org/html/draft-gredler-idr-ls-distribution-02> >>>> http://tools.ietf.org/html/**draft-ietf-alto-protocol-12<http://tools.ietf.org/html/draft-ietf-alto-protocol-12> >>>> >>>> Hope this helps. >>>> >>>> s. >>>> >>>> >>>> >>>> On Aug 3, 2012, at 1:29 AM, Robert Raszuk wrote: >>>> >>>>> Tom, >>>>> >>>>> I agree that one of the top work items for this effort should be a >>>>>> standardized topology function, and one that is accessible via a >>>>>> non-routing protocol. >>>>>> >>>>> So if the requirement is to have topology export via non-routing >>>>> protocol then I think we should seriously revisit or repackage the >>>>> draft-gredler-idr-ls-**distribution-01 which works for for both OSPF >>>>> and ISIS. >>>>> >>>>> However before that let's really understand the requirement why it >>>>> must be exported via non-routing protocol .... Keep in mind that just >>>>> to parse BGP UPDATE messages and retrieve interesting pieces out it >>>>> it requires very little code rather then full BGP implementation. >>>>> >>>>> The particular feature I like about >>>>> draft-gredler-idr-ls-**distribution-01 is that it is read-only ;) >>>>> >>>>> R. >>>>> >>>>> I agree that one of the top work items for this effort should be a >>>>>> standardized topology function, and one that is accessible via a >>>>>> non-routing protocol. While not exactly "low hanging fruit", it is >>>>>> something that (to me) is a clear work item with clear goals that >>>>>> should >>>>>> be tackled straight away. >>>>>> >>>>>> --Tom >>>>>> >>>>>> >>>>>> >>>>>> On 8/2/12 3:24 PM, "James Kempf" <[email protected]> wrote: >>>>>> >>>>>> So after seeing part of Alia's talk this morning (I had to leave in >>>>>>> the >>>>>>> middle unfortunately), I'd like to make a couple suggestions. There >>>>>>> were >>>>>>> a lot of ideas presented in the talk, enough for an entire IETF >>>>>>> Area. I >>>>>>> think to make tangible progress, the work needs to be focussed on a >>>>>>> small >>>>>>> subset that would be of immediate interest and usability. >>>>>>> >>>>>>> There are a couple areas that suggest themselves, but one that >>>>>>> would be >>>>>>> useful in work that I've been involved in is a standardized format >>>>>>> for >>>>>>> network topology representation and a protocol for exchanging it. The >>>>>>> Onix OpenFlow controller has a network information base with a >>>>>>> specialized format for network topology, and every OpenFlow >>>>>>> controller >>>>>>> requires this. Having a standardized way to represent it might >>>>>>> foster a >>>>>>> common topology database package. Another application is network >>>>>>> management. Every network management system needs some kind of >>>>>>> topology >>>>>>> representation. Finally, though I am not an expert in PCE >>>>>>> construction, >>>>>>> it would seem to me that a PCE would need some kind of topology >>>>>>> representation in order to perform path calculations. Having a >>>>>>> way,for >>>>>>> example, for the OpenFlow controller and the PCE to exchange topology >>>>>>> information would be really useful. I would say to start with >>>>>>> physical >>>>>>> topology because that is fundamental, but make the format flexible >>>>>>> enough >>>>>>> to support >>>>>>> virtual topology representation. >>>>>>> >>>>>>> jak >>>>>>> ______________________________**_________________ >>>>>>> irs-discuss mailing list >>>>>>> [email protected] >>>>>>> https://www.ietf.org/mailman/**listinfo/irs-discuss<https://www.ietf.org/mailman/listinfo/irs-discuss> >>>>>>> >>>>>> ______________________________**_________________ >>>>>> irs-discuss mailing list >>>>>> [email protected] >>>>>> https://www.ietf.org/mailman/**listinfo/irs-discuss<https://www.ietf.org/mailman/listinfo/irs-discuss> >>>>>> >>>>>> >>>>>> ______________________________**_________________ >>>>> irs-discuss mailing list >>>>> [email protected] >>>>> https://www.ietf.org/mailman/**listinfo/irs-discuss<https://www.ietf.org/mailman/listinfo/irs-discuss> >>>>> >>>>> ______________________________**_________________ >>>> irs-discuss mailing list >>>> [email protected] >>>> https://www.ietf.org/mailman/**listinfo/irs-discuss<https://www.ietf.org/mailman/listinfo/irs-discuss> >>>> >>> >>> ______________________________**_________________ >>> irs-discuss mailing list >>> [email protected] >>> https://www.ietf.org/mailman/**listinfo/irs-discuss<https://www.ietf.org/mailman/listinfo/irs-discuss> >>> >> ______________________________**_________________ > irs-discuss mailing list > [email protected] > https://www.ietf.org/mailman/**listinfo/irs-discuss<https://www.ietf.org/mailman/listinfo/irs-discuss> >
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