IETF-57 RTG area meeting minutes
Alex Zinin <zinin@psg.com> Tue, 05 August 2003 21:29 UTC
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Thanks to Ross and Dimitri, minutes from the meeting below. Folks who were at the meeting--please review and let me know if something is so inaccurate it should be fixed. -- Alex Announcements (Bill Fenner) - RIP working group is finished and will be ended - There is a routing area website: www.rtg.ietf.org - THere is a routing area mailing list: routing-discussion@ietf.org Working Group Reports IDR status (Sue Hares) - are in a holding patter until base spec is complete (are on -21) - see agenda for IDR working group IS-IS - no report Manet (Alex) - four protocol specification are going to experimental status AODV was published as RFC 3561 others in progress (one recently reviewed) Implementation is in progress Multicast Last Mile BOF - no report OSPF Status - two RFCs (NSSA 3101; 3509) - five documents in working group last call or beyond - OSPF V2 TE is through to the RFC editors - BCP prioritization fo OSFP packets - refresh reduction in stable topologies - two mibs and v3 and authentication for V3 need more work - two new documents are just starting at this IETF MSDP - document done - MIB almost done PIM - three major drafts in progress - they have been pretty stable for a while - trying to arrange appropriate reviewers RPSec - didn't meet SSM - didn't meet at this IETF UDLR - no meeting (but status report) - 30 June, submitted revised version - Major changes from v00.txt (now v01.txt) . write PPPoE experiment . wrire PIM-SM and MSDP experiment . add NAT - IPv6 over UDLR . no exp i-d . 18 june, start discussion on mailing list . if there is common interest make a draft charter an propose to AD's VRRP - Radia Perlman is now co-chair of the group - security has been removed from VRRP after considerable discussion - v2 and v3 drafts have been updated. V2 is ready for WG last cann as draft standard. VRRPv3 MIB has just been submitted to the working group, and needs review. UDLR - no report IP Forwarding MIB (Brian) a while ago updated MIB support for IPv6 requested. Most of these are in last call in the IPv6 working group. A request: Why not fix other stuff, such as making it easier to support in today's forwarding engines? This work is starting now that the IPv6 is stable. Question to people designing forwarding engines: Is the current IP Forwarding MIB that is currently defined for IPv4 useful at all? If not, should we fix it now. Send opinions to Bill Fenner of the routing area mailing list. Panel: Routing Protocol Overload Panelists: Dave Meyer Pedro Marques Ron Bonica Gargi Nalawade Introduction by Alex: Why are we here: Community is polarized over use of routing protocols for uses which go somewhat beyond the narrow definition of routing (particularly wrt BGP). Alex would like to see the community talk. Alex characterized the two viewpoints as: Camp 1: - MP-BGP framework is a useful tool to distribute info among INET routers - Fair treatment of different AFI/SAFIs is an implementation problem - We know how to do this, leave this to us Camp 2: - This is dangerous. Risks the Internet. Any instability or code complexity caused by one use of BGP could destabilize the main purpose, which is Internet inter-domain routing. Alex would like us to walk out of this room with some understanding of where we are going. He would like us to find a common ground. Please respect other points of view. Please don't bring personality issues to the discussion. Don't just state your opinion, but instead explain the reason for the opinion. Panelists present their opinion: Dave Meyer: - Musings on NLRI loading, stability, and signaling in the Internet - It is hard to get hard evidence on what we ought to do. Maybe we need a study on the topic. - BGP and maybe IGPs can form an effective transport for new features. - BGP is also used in the Internet - BGP in the Internet can have stability issues in some cases. - It seems reasonable to ask what effect loading BGP with other information will have on routing stability. - Dave can't quantify anything about the stability. Dave has talked to a lot of people. Plusses: Operational simplification; Code Re-Use; BGP code will be carefully optimized. - Operational complexity: Worry about breaking one thing when doing something else. Single point of failure. Internal queue management needed. - Much of this is conjecture. - What if we wanted to start from scratch: Would we want a generalized feature transport Mechanism? If so, is BGP this mechanism? As an example MSDP ended up looking a lot like BGP. - Proposal: create problem statement. Draft Requirements, framework and architecture. Perhaps we should present a problem statement at the next IETF. Ron Bonica - Defining the scope of BGP - Background on the problem: Routers support many applications which require the synchronization of databases on multiple routers. - BGP could support all of these applications. - Ron echoed concerns that he has heard: Will BGP get buggy as we make it more complex? Is there a possibility of mis-configuration: As functionality increases, will information be leaked incorrectly between service providers, and possibly be mis-interpreted? - Mitigations for these concerns are available: BGP software is already fairly modular. Data transfer is separate from other functions. This implies that as we add more to BGP, we add new modules. Controls exist to protect against mis-configuration. - Big Bug issue: What if something really bad happens? - BGP incomprehensibility: What if it gets too big for a human to understand? - Perhaps we should document BGP as a number of separate modules. - Options - restrict BGP to main use, and clone it for other reasons - abstract data transfer from other parts - let BGP grow - None of these solutions are necessarily right. - if clone, end up fixing same bugs in multiple code bases and updating code multiple times - We are on shaky ground in taking on this issue. Most of this discussion is about software engineering. The IETF doesn't normally do software engineering. - Proposal: That we listen to vendors and operators. Study the issue. Pedro Marques: - (Mostly agree with Dave. This is an issue to study) - Look at this from the point of view of System Availability in Multiservice Networks - What is router availability? - What does it depend upon? - Is there is an impact on deploying a new service in the router? Yes. - Don't just look at one component of this. Look at overall system and network availability. The resource sharing issue surfaces whenever you introduce a new service on the router. However, resource sharing is also an issue when you have only IP Internet service (eg, sharing between BGP and an IGP; sharing between multiple BGP neighbors, so that one neighbor doesn't seriously impact another). - System availability is a system design issue. There are significant software engineering aspects of this. System availability is generally improved by maximizing code re-use. This leads to fewer defects. - The most problematic issue is internal infrastucture changes (internal to the router). This is independent of the protocol issue, and independent of anything that we do in the IETF. - If a given problem requires point to multipoint distribution of information, then re-use of BGP is more cost-effective than inventing a new solution. - Summary: Resource sharing is always an issue. This is not limited to multi- service issues. There are serious issues here, but these are primarily software engineering issues and therefore outside of the scope of the IETF. Gargi Nalawade - Consider "Routing Protocol Overhead". - What is BGP: A routing protocol, or a database distribution protocol? - If it is a routing protocol, should it be doing database distribution? - If it is a database distribution protocol, should it be doing routing? - BGP definitely does routing. If it does both, what % of its task should be doing routing? - Question is not whether BGP can do this, of course it can. But the question is whether BGP should do this. - Routing related information which is closely tied to BGP must be carried in BGP. - What's the solution: Identify the problem. What is routing related? Then we can talk about solutions. - This is not just a BGP issue. IGPs carry opaque LSAs and/or extensible TLV. Why have a BGP-specific solution. - She agreed with Pedro that cloning is bad for the health. Open Discussion: - Yakov: Gargi's comment that she doesn't want BGP to carry Shakespeare is not relevant to the discussion. The decision should be based on a cost/benefit analysis, not on what she wants. - Mark Handley: We might want to distinguish Protocol implementation overloading, versus protocol instance overloading, versus protocol design overloading. Instance is most important. We are talking about fate sharing; If you have two services sharing the same protocol, then they share the same fate. If two services need to be coupled then fine, but otherwise don't put them in the same protocol instance. Congestion control sharing is also potentially an issue. Example from different world (SIP): SIP was designed to operate over <didn't hear>. Then SIP got instant messaging added to it, then it was realized that instant messaging included video, this was too much, then they fixed it by removing some features and handling them otherwise. - Chandra (from cisco): The concerns that people have expressed are not clearly articulated. Are we talking about overloading the protocol, versus the implementation, versus a protocol instance? These are not the same, and he doesn't know which one is the concern. Is this an issue of configuration modules, or software implementation? If this is a configuration issue, then you can fix this as a configuration issue and not as a protocol design issue. - Dave Meyer wants to understand whether putting more into BGP effects global Internet stability. - Rahib: What if any impact will this have on the scalability of the routing protocol? - Rob (Austein): Has spent time with DNS. When you keep adding features to a protocol, pay attention to who gets benefits and who suffers the pain. - Kurt (Lindqvist) We are getting lazy: We are trying to make it easy by using the same protocol over and over. The threshold for adding things to the protocol is too low. Where does this end? - Kireeti: Don't ask if you are overloading the protocol or system. Ask about multiservice platforms: Is this a good idea? The resource contention comes from having multiple services on the same physical platform. Do we want a box doing IP, and a different box doing L2VPNs, and a different box doing L3 VPNs, etc.. The issue is whether we put these in one box or in multiple boxes. If the box falls over, then you have taken down whatever is on the box. Putting multiple services on the same box will have an impact, and therefore require careful implementation. Whether you put them in the same protocol is at the most a second order issue. It is normal for reachability information and routing information to be in a routing protocol: An IP VPN prefix is reachability information. A layer 2 prefix is reachability information. - Ross Callon: Some have talked about software engineering, others have expressed concerns about internet stability and a few said "I don't care about software engineering, I care about Internet stability". We need to understand that software engineering is a major impact on Internet stability, and thus the people who are talking about software engineering are talking about internet stability, and are trying to address what is the most critical part of Internet stability. Using the same protocol does not preclude a careful partitioning of resources within a device, nor does it preclude using separate TCP connections. Using a different protocol does not guarantee using different resources: If multiple services are in the same physical device, at some level there will be some sharing of resources. Therefore the primary issue is not the protocol. The primary issue is the services on the box, and how much information needs to be exchanged between the boxes. Adding new services to the box requires new information. This will have some impact. Ross has heard comments from multiple service providers that they don't want ten different types of boxes in their network, so they want multi-service devies. The issue is then how best to provide this. - Someone from UUnet/MCI: BGP and IS-IS are sort of bread and butter for us. They want these protocols to be solid. At one point when IPPPN got added to code base, it caused a major outage to their network, even though they didn't use it. This is because it impacted the software on their machines in a negative way. Once you put a new feature into the box, particularly into the same protocol, will this cause a problem - possibly even if they don't use the feature? They run the same code in the core as in the edge, even though they don't need the same features in the core. They can turn off a protocol, if things are in a separate protocol. Reply: You can turn off the address family. - Hamid (I think that this was Hamid Ould-Brahim): Before a routing protocol becomes a protocol, there is a set of problems that the working group looks at. If a different working group faces the same problems, then they tend to select the same solutions. He doesn't see a problem here. In many cases when distributing other sorts of information, you end up facing the same problems. Thus you may use the same solutions, such as using route reflectors. Thus you can gain from experience. This is a natural way of solving problems. - Lixia Zhang: Good software engineering can reduce the number of bugs. However, the number of bugs will grow faster than linearly. More modular code will help. We are not just here to build protocols. - Pekka Savola: Do we want multiple services or not: In their network, then definitely don't want them. Pedro: No vendor will build a product for a single company, or even for a limited market segment. Enterprise features, X.25 tunneling features will get added. There is the potential for impact. How do we design things in the most reasonable way to minimize the amount of new code which is needed to provide a certain set of functions. If you have one problem then if you re-invent the wheel. - marlove(?): He is only three years out of college, and remembers his software engineer course: But I didn't get his point. - Gargi: Whether or not it is a new protocol there may be some code re-usability. - Luyuan Fang: I agree that there are two problems: Code and mis-configuration. Our configuration of BGP for Internet routing, and our configuration of VPN services are separate. Thus having the same protocol does not require having a single configuration tool. Are we talking about multiple services on one box, or a single service per box? They are putting multiple services on one box. They are going to consolidate even more. A University network might not need as many services. As a large service provider, they can't afford to put ten different boxes into their network to support ten different services. Luyuan feels we should eave it up to the vendor to determine the best way to make this reliable and robust. We can't stop progress, we need to standardize how to offer the multiple services on one box. It doesn't matter to them whether it is one protocol or multiple protocols. - Alex: in the life of a protocol, there will be times when you need to think carefully about whether or not you want to extend the protocol further, or start new protocols. - Curt: We have enough to do operationally just to get packets forwarded. I am not so worried about adding more lines of code to the routers. I am more worried about having that code executed. I want to know what I am running. When we got the problem with BGP: We had the VPN code in the BGP. We got the problem because the code was delivered in the software. It was a vendor coding thing, but this is going to happen. Different BGP configuration has already been done with the consideration that BGP is only doing IP routing. Other services might have a different characteristics in terms of how rapidly data is updated / exchanged, hold down timers, for example. - Andrew(?): We need to separate concerns about bugs versus features. Bugs do happen. Don't let one particular bug that occurred in one implementation obscure the entire conversation. The code has to evolve. - someone from DT (Rahul Volk?): Talking about design or architectural principles sometimes get into fuzzy areas. Since Roman time, we have had divide and conquer as a principle. Using the protocol which is already there to improve TTM doesn't seem right. There is a tradeoff between code reuse and speed of deployment, versus adapting the solution for problems that are not foreseen. - Pedro: Someone made a comment before regarding who pays the cost of adding functions. No customer has ever said "do it perfectly, and we will wait five years for it". If customers were to say this, we will respond to it. Cost and who are willing to pay matters. - Alex: If we look ten years ahead, do we want a very large number of attractive features implemented in BGP, or do we want something else. - Pedro: Ten years from now, there will be a protocol called BGP, which will have almost no resemblance to what is there today. Unicast routing will evolve over time. Technology goes in cycles. Today the stimulus is for VPNs. Next year it may be something else, and BGP will evolve to handle this. - Gargi: We will always have short term requests. This should not preclude us from looking for a long term solution. Putting things into BGP might be the correct long term solution, but we should investigate whether this is the right thing to do. - Ron: If we were doing BGP over again, we might want to design two protocols, a generic data transfer protocol, and a routing protocol which computes routes, and which uses the data exchange protocol to carry its routing information. - ?? (didn't get who): in the short term we have a set of vehicles and a set of problems. - Rahul Aggarwar: Three issues: (i) Protocol overload; (ii) implementation complexity / software engineering; (iii) Deployment issues. How strongly coupled are the new features with the old features in BGP? Probably not very. If we put new information into BGP and carry it around, is this a problem. - Bill Fenner: There has been a lot of work on the stability of routes in BGP and the stability of inter-domain routing. If you put more things over the same protocol, are you violating the original assumptions. - Gargi: Just because you use a new SAFI, there is still some impact on the overall BGP. Existing SAFI's may be effected. - Rahul reply: He is making a distinction between code changes and protocol procedures. - Dino: MSDP: Why was this not in BGP: Multiple service providers said that they wanted it in BGP in order to make it easier to deploy. Dino had a concern that it might evolve after deployment, and that this might have future impacts on BGP which we can't anticipate. Also, if it fails, then it is easier to remove if it fails. If you want things stable, you can't change it. Pedro questioned whether this was an appropriate analogy. - Yakov: If I follow your logic, then we should take multicast and IPv6 out of BGP, and have four protocols (unicast IPv4, multicast IPv4, unicast IPv6, and multicast IPv6): - Dino: It is a cost-benefit tradeoff. - Yakov: We agree that it is a cost-benefit tradeoff. BGP was designed to carry 1,000 routes. BGP was not designed to carry CIDR, nor IPv6. BGP carries much more than this today. It has evolved over time to meet new requirements. We have other precedents of putting multiple things into one protocol: Two such precedents are IP and TCP. In order to decide what should go into BGP and what should not go into BGP requires cost-benefit analysis. If you want to add something which folds in well, you do so. If you want something that requires very different procedures, then you use a new protocol. - Vach: Cost benefit analysis is a way to consider alternatives (eg, use a linked list or use a tree - this is a cost-benefit analysis). Using a flooding protocol for information which doesn't need flooding is a good example of a bad tradeoff. - Chandra: We know that BGP can be extended to have multiple sessions (eg, per-SAFI). BGP can therefore become a session demultiplexer. I am getting the feeling after listening to this that some people feel they can drive protocol implementation architecture by driving one or multiple protocols. Panelist summaries: - Ron: software is about software extensibility and stability. These are software engineering issues, and the IETF doesn't do software engineering. Others have pointed out that we want modularity but we can't force any particular software design by deciding what goes into what protocol. This implies that we have a really hard problem. - Dave: Wants to talk more about protocol design and less about software design. There is a tradeoff between features and bugs. We can't get away from that. What is the effect on the Internet architecture. - Pedro: What are the concerns that people have? He would like to get the concerns enumerated so that the concerns can be understood. - Gargi: Has heard concerns from operators that they want the core Internet functionality to be solid, and not impacted by any additions. Whether something belongs in BGP needs to be handled on a case by case basis. Even though some things may look okay in BGP today, we also have to pay attention to whether this will belong in BGP in the future. Questions from Alex: - How many ISPs ? ~ 10 - Who thinks BGP overloading is not an issue ? ~ nobody - Who thinks BGP should not change at all ? ~ very few - Who believes we should pursue the direction of a new protocol potentially based on MP-BGP framework and used for distribution of generic non-routing related info among the routers? ~ lot of support _______________________________________________ routing-discussion mailing list routing-discussion@ietf.org https://www1.ietf.org/mailman/listinfo/routing-discussion
- IETF-57 RTG area meeting minutes Alex Zinin
- Re: IETF-57 RTG area meeting minutes Manav Bhatia