Short version: I believe the GLI-Split designers were mistaken to class their proposal as a Core-Edge Separation (CES) architecture. I am sure it is a CEE (Core-Edge Elimination) architecture.
Comments on Lixia's and colleagues' 2008 paper on Core-Edge Separation vs. Core-Edge Elimination. I think they were mistaken to class GSE as a Core-Edge Separation architecture. I think this paper refers generally to the core-edge "separation" being of the routing systems of the edge networks from the core - but the real distinguishing thing about CES is the separation of one subset of global unicast address space into a "edge" subset for scalably supporting end-user networks with multihoming etc. from the remaining "core" addresses. The authors were in general the designers of APT, which separated not just the address space into two subsets, but had a long-term goal of actually separating all the edge networks from the core, so no edge host could physically send a packet to any core address. AFAIK, no other CES architecture is intended to separate the routing systems like this. I think this double sense of the term "separate" plus the mistaken classification of GSE as CES contributed to the GLI-Split authors considering their proposal to be a CES architecture too. Yet it is clearly CEE, since it implements the Locator/Identification Separation naming model. These terminological and classification problems are compounded by LISP being inappropriately named - since it is a CES architecture which does not implement Locator/Identifier Separation. Six/One Router is a translation-based CES architecture. GSE and GLI-Split are translation-based CEE architectures. They are unusual among CEE architectures in that they only require the new router functions and changes to the stack - they do not require applications to be modified. (However I just learnt that GLI-Split could support new application functionality via a new API.) Comparison charts of: CES: LISP-ALT/NERD, APT, Ivip, TRRP, TIDR, IRON-RANGER and Six/One Router. CEE: GSE, GLI-Split, ILNP, Name-Based Sockets. Here is some discussion further to my understanding of the distinctions between Core-Edge Elimination (CEE) architectures and Core-Edge Separation (CES) architectures: CES & CEE are completely different (graphs) http://www.ietf.org/mail-archive/web/rrg/current/msg05865.html This paper: Towards a Future Internet Architecture: Arguments for Separating Edges from Transit Core Dan Jen, Lixia Zhang, Lan Wang, Beichuan Zhang http://conferences.sigcomm.org/hotnets/2008/papers/18.pdf is really important to the RRG discussions, because it formalises the architectural terminology for two important classes of scalable routing solution. To see my attempt to trace the origins of these concepts and terms, please see: Re: [rrg] Terminology http://www.ietf.org/mail-archive/web/rrg/current/msg05966.html I support this paper, but have some comments to make: 1 - The definition of exactly what core and edge things are being separated or eliminated could be improved - to refer to separation into two subsets of addresses. 2 - The suggestion that GSE is a CES architecture is mistaken. 3 - The paper doesn't mention what I consider to be the biggest objection to CEE: that it implements the Locator/Identifier Separation naming model which will generally slow down the establishment of communication sessions and place extra burdens on all hosts - especially those on slow, unreliable wireless links. The paper refers in general to: "separating edge networks from the transit core" but really both CEE and CES maintain the already existent separation between edge networks from the transit core. (See discussion of section 4.3 below for my understanding of why the authors may have emphasised the separation of networks rather than the separation of a new subset of scalable "edge" addresses from the remaining "core" addresses. The intended APT to ultimately separate the two systems so much that an edge host would be physically unable to send a packet to a core router.) What is being separated in a CES architecture is the "edge" subset of addresses from the remainder of the global unicast addresses, which is then known as "core" addresses. This is a different separate concept from "separating edge networks from the core", since the networks are already separated. Its just that at present, these PI prefix-using End User Networks (EUNs) use address space which all core (DFZ) routers need to be concerned with. >From the abstract, it can be seen that the CES definition is not the opposite of the CEE definition: CES: The first direction, which we dub separation, calls for separating edge networks from the transit core, and engineering a control and management layer in between. CEE: The other direction, which we dub elimination, calls for edge networks to adopt multiple provider-assigned addresses to enable provider-based address aggregation. (See below for discussion of the paper's more formal description of CEE.) In fact, the CEE definition could reasonably include CES architectures, since CES architectures generally use multiple ETRs, each on a PA ("provider-assigned") address, for the purposes of enabling the DFZ to only handle prefixes which are subject to "provider-based address aggregation". The most important architectural distinction between CES and CEE is: CES involves end-user networks' hosts using global unicast addresses from a specially handled "edge" subset of the global unicast address space, with the remainder being known as the "core". IP addresses in both subsets will continue to be used, as are all today, both for Identifying hosts and for the Routing system to decide how to forward packets (i.e. "Locator). But note that CES has a new, fancy, way of doing this for this subset of "edge" addresses - different from today's plain DFZ approach - which is highly scalable and allows these "edge" addresses to be used by EUNs for portability, multihoming inbound TE and perhaps for mobility. CEE involves end-user networks' hosts using something other than a global unicast IP address to Identify themselves. Thus CEE implements the Locator/Identifier Separation naming model. Applications use this new Identifier, which is in a different namespace to IP addresses and any Locators used in the system, to identify each host. Hosts can be reached via one or more potentially unstable Locators, and the applications are unaffected due to their reliance purely on Identifiers to specify which hosts are communicating. CES preserves the existing IP naming model: Role Level Text name <---- FQDN Identifier <---] IP address Locator <---] while CEE creates one of several models, in which the Locator and Identifier roles are played by different levels - different objects in different namespaces. CEE architectures always implement Locator/Identifier Separation. No CES architecture implements Locator/Identifier Separation. What they separate is two subsets of the global unicast address space: "edge" from the remaining "core". Both types of address are used both as Locators and as Identifiers. Both subsets are used as Identifiers by all hosts. Hosts make no distinction between addresses in the two subsets. Most routers make no distinction between how they handle packets with destination addresses in these two subsets. The exception is ITRs, which make a big distinction. ITRs implement the Locator functionality of "edge" addresses in a totally different way: by looking up mapping and tunneling to an ETR, rather than by forwarding the packet to a neighbour. More on naming models: Today's "IP addr. = ID = Loc" naming model should be retained http://www.ietf.org/mail-archive/web/rrg/current/msg05864.html CES architectures never require changes to host stacks or applications. Many CEE architectures require changes to both stacks and apps, but at least two - GLI-Split and I think GSE - only require changes to the stacks. Here are some cases: CES: LISP, APT, Ivip, TRRP, TIDR and IRON-RANGER. There's no debate about this - they all create a special "edge" subset of the global unicast address space for EUNs to use for portability, multihoming, TE and perhaps mobility - and add things to the routing system to scalably get packets addressed to "edge" addresses to the destination networks without excessive burdens on the DFZ control plane. Except for Ivip's long-term "Modified Header Forwarding" modes, all these use encapsulation in order to tunnel packets from an ITR or ITR-like device to an ETR or ETR-like device. This raises some thorny PMTUD problems. These CES architectures are all intended to work for both IPv4 and IPv6. The descend directly or indirectly from the original map-and-encaps architecture. No host stack or application changes are required. Things are added to the routing system - but in general routers stay the same. CES: Six/One Router - by Christian Vogt, though AFAIK it is no longer under development. http://conferences.sigcomm.org/sigcomm/2008/workshops/mobiarch/papers/p13.pdf This is clearly a CES architecture, because the end-user networks operate from a single prefix drawn from an "edge" subset of the global unicast address range. (Sect. 2.1.) Figure 1 illustrates this setup and addressing for an edge network that is multi-homed with two providers. This edge network has one border link to each provider, so two Six/One routers are in use. The edge addresses are from the ---- prefix ABC::/64. The Six/One router on the border link to provider 1 translates between those and transit addresses from the prefix 1000::/64; the Six/One router on the border link to provider 2 translates between the same edge addresses and transit addresses from the prefix 2000::/64. A host HA in one Six/One Router network, addresses packets to a host HB in another Six/One Router network another using the same IP address in the destination field as HB uses as its own "edge" address. Edge addresses are for use within this and other upgraded edge networks. They are globally unique, but do not appear --------------- in the global routing table because they cannot be efficiently aggregated. All hosts in Six/One routers use a form of DNS which returns these "edge" addresses for any host in any Six/One Router network. So this is a genuine scalable "edge" subset of the global unicast address space. However, because Six/One Router has no equivalent to DITRs (Ivip) or PTRs (LISP), hosts in ordinary IPv6 networks can't send packets to the Six/One Router hosts using these scalable "edge" addresses. So, from a non-Six/One Router network, a DNS lookup on the same FQDN of host HB will not return its "edge" address, but one or more another addresses, based on one or more addresses within the PA prefixes HB's network obtains from its one or more ISPs. The address-rewriting router at the border of HB's network will rewrite the destination address of a packet coming from some ordinary IPv6 host HX, to the "edge" address of HB. This is explained in section 2.4. No other CES architecture has this "split-horizon" (I think this is the right term) DNS arrangement. I guess it was impossible to implement an equivalent of DITRs and PTRs. The hosts in Six/One Router behave as usual. There are no stack or application changes. The naming model used in the packets they send and receive is the same as with today's IPv4 and IPv6, as illustrated above. Rather than tunnel packets across the DFZ with encapsulation or Modified Header Forwarding, Six/One Router uses address rewriting (AKA address translation) at EUN BRs or perhaps in a router in their ISP(s). Unfortunately, Six/One Router can't be used for IPv4 due (I guess) to the more chaotic EUN prefix lengths and (I am sure) due to the need for a 2 ISP multihomed EUN to consume 3 times the amount of global unicast address space it really needs. (One for its "edge" prefix and then the same amount of PA space from each of its ISPs.) Also, when Christian and I last discussed it on the RRG, he wrote that he needed a flag bit from the IPv6 header, which would require a modified IPv6 header format and so require updates to all DFZ and many other routers. CEE: GSE - Mike O'Dell, 1997 http://ietfreport.isoc.org/idref/draft-ietf-ipngwg-gseaddr/ This is an extension of his earlier 8+8 architecture - both are for IPv6 only. GSE is clearly a CEE architecture because it has separate objects for Identifying hosts and for Locating them. There is no separate "edge" subset of the global unicast address space by which hosts in EUNs identify themselves. The Identifier is the 64 bit ESD. There needs to be new things in the network: an address rewriting function in the BRs of EUNs which adopt GSE. Host stacks needs to be somewhat modified, but I think this is mainly so header checksums are computed only on the ESD and not on other parts of the IPv6 address. As far as I know, applications do not need to be modified. Multihomed EUNs get a prefix from each of their two or more ISPs, and the identity of hosts is unrelated to this, or to any IP address. These prefixes are PA, and the ISP may have a single large (short) prefix which it splits into many such prefixes for many such EUNs. Host Identity - and so all communications establishment and session continuity - is determined by the value each host uses for the 64 bit ESD, which exists in a separate namespace from IPv6 addresses. CEE: GLI-Split http://www3.informatik.uni-wuerzburg.de/~menth/Publications/papers/Menth-GLI-Split.pdf I believe GLI-Split is a CEE architecture, because it introduces a separate "ID" object (Figure 2), with a separate namespace from IPv6 addresses or anything else, to Identify each host - which is different from the objects used to Locate them: the GL or LL Locators. The fact that both objects are combined with other things to form an IPv6 address does not affect the fact that these objects for Identifier and Locator are independent, and in separate namespaces, just as they are in ILNP, GSE and the other CEE architectures. GLI-Split implements Locator/Identifier Separation, as do all other CEE architectures. From the Abstract: It implements the locator/identifier split and makes routing in the core of the Internet more scalable. More on GLI-Split at the end of this message. The authors explicitly state that it is a CES architecture, but I am sure it is a CEE architecture. I think they are following a mistake made which I believe was made in the the 2008 sep./elim. paper. CEE: ILNP - Ran Atkinson. This is clearly a CEE proposal, because it has separate levels for Identifier and Locator. It is a purely host-based descendent of GSE. There is no need for new routers, but the host stacks and applications all need to be upgraded, because the applications use Identifiers and Locators separately via the API to the stack (or do the applications use only Identifiers?). As with GSE and all other CEE architectures, a multihomed network uses two or more PA prefixes from its two or more ISPs, and the PA nature of those prefixes means each ISP can supply many such prefixes from a single prefix the ISP advertises in the DFZ. CEE: Name Based Sockets - Christian Vogt. This is a CEE architecture because the Identity of each host is a FQDN and its one or more Locators are IPv6 addresses, again drawn from PA prefixes of the EUNs one or more ISPs. Name Based Sockets is unusual for a CEE architecture in that it appears to have a two-level naming model. However, I am not sure how it could have this and still be able to support DNS lookups leading to multiple separate hosts. I hope Christian will clarify this. CEE? RANGI and Name Overlay Service I am yet to read these properly, but my impression is that they are both CEE architectures. ???: hIPv4 - Patrick Frejborg I think this was an attempt to create a new, larger, address space while enabling scalable routing and transport of the new format packets across the DFZ. The ELOC part of the new address is not globally unique. (If it was, it would be an Identifier.) The combination of the ALOC and ELOC provides the extended equivalent of an IP address today - meaning both a host Identifier and including a routing locator within the one object. I previously thought it was a CEE but I think it is neither CEE or CES. Unfortunately, hIPv4 is not practical since DFZ routers are not ready to handle packets with the required option header. ???: Aggregation with Increasing Scopes. I don't yet understand this. Here are some charts: CES IPv4 IPv6 Tunneling Local Mapping architecture full- speed database mapping servers? LISP-NERD v4 v6 Encaps. ITRs are full Slow database LISP-ALT v4 v6 Encaps. No Global lookup ALT v4 v6 Encaps. Yes Slow Ivip v4 v6 Encaps. Yes Fast or MHF TRRP v4 v6 Encaps. No Global DNS lookup TIDR v4 v6 Encaps. ITR-like Slow - via DFZ routers DFZ control have full DB. plane. IRON-RANGER v4 v6 Encaps. (Neither question applies directly to IRON-RANGER.) Six/One Router v6 Address (Six/One Router's mapping rewriting system was never specified.) CEE IPv4 IPv6 App Stack Router changes? changes? changes? GSE v6 - Stack Router rewrites GLI-Split v6 -* Stack Router rewrites ILNP v6 App Stack - Name Based Sockets v6 App Stack - * GLI-Split does not require host changes, but Michael Menth just wrote to me offlist that new applications could be used, for instance for multipath protocols, if the stack had a suitable new API: "Applications usually communicate with identifier addresses, but also a more advanced API must be offered in addition to allow active multipath routing through applications or at least by transport layer protocols. He indicated that this was not in the current documentation but would be added in the future. Back to the 2008 paper: on page 2, 2nd last paragraph: There are also other types of separation solutions besides Map & Encap. For example, Six-One Router [23] and GSE [19] use address rewriting, which rewrites the packet header to include information about the destination’s attachment point to the transit core. For the reasons listed above, I believe GSE is a CEE architecture. The fact that the CES architecture Six/One Router has routers rewriting addresses does not mean that GSE is a CES architecture simply because it too has routers rewriting addresses. In Section 3, there is a more formal description of CEE: In order to achieve routing scalability, the elimination approach enforces provider-based address aggregation by eliminating all PI prefixes and de-aggregated PA prefixes. I wouldn't state it so strongly. I think it is more accurate to say that when all hosts in all networks adopt CEE, the CEE mechanisms can be relied upon entirely for portability, multihoming and inbound TE. Then, and only then, this means that no network needs PI space to achieve these things. This doesn't mean that PI space (the current, unscalable, form of "edge" space) would automatically be eliminated - just that it could be eliminated without any network missing out on portability, multihoming or inbound TE for all its hosts and communications. Each multihomed edge network will receive from each of its providers an address block out of a larger, aggregated block announced by the provider. I would rephrase it slightly. Each EUN which adopts CEE would generally use space like this. Each such EUN *could* use PI space. Its just that PI space is no better than PA space for use with a CEE architecture. (Likewise a EUN using a prefix it gets as PA space from one ISP via another ISP as a "more specific PA prefix" - which also has the effect of adding another prefix to the DFZ control plane.) The degree to which they can multihome etc. depends on how many of the hosts they are communicating with are also using the CEE architecture, as noted in 4.1. The multihomed site does not inject PI prefixes or more specific PA prefixes into the routing system. Instead, each host in a multihomed site is given multiple PA addresses. For example, as shown in Figure 2, the host obtains two addresses, one from each of its network’s ISPs. Typically, this is what would happen. The "elimination" in this description refers to the elimination of a class of address space, the current unscalable "edge" subset which is primarily PI prefixes and also, to some extent (I don't know how much) these "more specific PA prefixes". The paper's initial use of "separation" was not in terms of address space, but in terms of separating edge *networks* from the core. Edge networks are always separate from the core. I think that a more correct use of "separation" would be to refer to the deliberate creation of a subset of "edge" space which can provide what EUNs need, but in a scalable manner. Then, there will be more EUNs getting the portability, multihoming and inbound TE they need, with less and less of them using PI prefixes or "more specific PA prefixes" to get it - which are also "edge" uses of address space, but the kind we are trying to discourage because they are unscalable. In section 4.3, I think I see why the authors refer more to separating edge networks from the core. I think what they are referring to is the end-point of APT adoption: 1 - All EUNs use APT, and so use the scalable "edge" subset of the global unicast address space. 2 - Therefore, no EUN needs PI space or "more specific PA prefixes". So these are all converted either to the new scalable "edge" subset of space or to the remainder - the "core" subset. 3 - Therefore, ISPs advertise prefixes into the DFZ which are all in the "core" subset. 4 - Because all ISPs and EUNs use APT, there is no need for APT's equivalent of LISP's Proxy Tunnel Routers or Ivip's DITRs. (APT's arrangement was never well documented, but it too could provide full support for packets sent from non-upgraded networks.) Therefore, there is no need to advertise any "edge" space in the DFZ. 5 - Now, if it was desired - as the APT designers desired - it would be possible, in theory, to prevent any host in an EUN from being able to send a packet to any host or router on a "core" address. Hosts in EUNs only need to communicate with other hosts in EUNs. (Traceroute and ping wouldn't concern DFZ routers, since all packets between EUN hosts would be tunneled across the DFZ.) Most of the APT designers wrote this 2008 paper. AFAIK, no other CES architecture had this complete, physical, separation of EUN hosts from being able to send or receive packets to or from "core" addresses as a goal. I specify it as a non-goal for Ivip. >From section 4.3: Separating edges from the transit core provides additional features that are sorely missing in today’s Internet. With separation, an end host can send packets through the transit core, but can no longer address a packet to any specific device inside the transit core. Although the separation does not eliminate any specific security threat, it raises the bar against malicious attacks targeted at the global routing infrastructure. In addition, the mapping layer between edge and core networks can serve as a mounting point for badly-needed control and protection mechanisms, and can also act as a cushion layer between the edge and core, allowing each side to deploy innovations without any involvement of the other side. We now elaborate on each of these benefits. They go on to discuss "Rolling out new protocols." and "DDoS mitigation." which they argue would be possible or easier only with complete separation of the "edge" networks from the "core" networks. I don't agree with these benefits, and I doubt it would be feasible to achieve such complete separation. I won't mention why, because that is not the point of this discussion. I am trying to explain why the authors of this important paper seemed to equated, in my terms: Separation of a subset of the global unicast space into a scalable "edge" subset. with: Separation of the "edge" networks so their hosts couldn't send packets to, or receive them from, devices in the "core". They also mention a third argument for this "separation": "Ingress traffic engineering.". I have two comments about this. Firstly, inbound TE works fine due to any amount of adoption of the CES architecture (that is separation of the scalable "edge" addresses into a subset) and does not depend on the complete separation of "edge" from "core" networks, which is what this section 4.3 concerns. As long as the CES architecture supports all packets sent from non-upgraded networks, inbound TE will be for all the adopting networks incoming packets, no matter how many other networks have so-far adopted the CES architecture. Secondly, what they write in the second paragraph about Site1 having preferences for which of Site2's two or more ETRs to use doesn't strike me as part of most CES architectures. I think the aim of most CES architectures is to to have the recipient site control which of its ISPs the packets arrive via. This is inbound TE. Maybe APT had some concept of the sending EUN controlling this, but I guess most sending EUN wouldn't care which ISP the packets went to. I think the discussion in section 5 about multipath being used with CES is not really about multipath as some other people conceive of it. My understanding of true multipath, such as MPTCP, is the sending host (or perhaps a router)and perhaps the receiving host (or its router?) being able to choose which of multiple ISPs in the sending host's network packets may go out from, at the same time as choosing which of multiple ISPs in the recipient host's network the packets will travel through. With CES, I don't see how a sending host could affect either. The routers in the sending host's network can choose which ISP link to send out the packets on (assuming the ISPs accept packets with "edge" addresses, which they will when CES is widely used). If those routers are ITRs, then in some or many CES architectures (but not Ivip) then perhaps the ITR might be locally programmed to prefer one of multiple destination ETRs over others - so in principle the ITRs in the sending network could affect the incoming load balance of the destination network. However, as far as I know, the intention with all CES architectures is to allow the sending network to choose the outgoing ISP and the recipient network to choose (inbound TE) its incoming ISP(s). In the case of Ivip, the recipient network only provides a single ETR address, so there is no option for the sending network to have its ITRs tunnel traffic to some other ETR of the destination network. I think this paper doesn't mention what I regard as the greatest objection to CEE architectures - their adoption of the Locator/Identifier Separation naming model, as I discuss in (msg05864). I the GLI-Split authors were mistaken to state that GLI-Split is a CES architecture. The summary: http://tools.ietf.org/html/draft-irtf-rrg-recommendation-04#section-10.1 includes text indicating that perhaps the authors consider GLI-Slit to be a CES architecture: GLI-Split implements a separation between global routing (in the global Internet outside edge networks) and local routing (inside edge networks) and using global and local locators (GLs, LLs). Yes, but all EUNs have separate routing from the DFZ - so this is not a function of GLI-Split. o Hierarchical aggregation of routing information in the global Internet through separation of edge and core routing. These phrases seem to imply that GLI-Split is a Core-Edge Separation architecture. Back to the GLI-Split paper, there is explicit recognition of how it involves the separation of Locator and Identifier functions. This is a feature of all CEE architectures, and is not (despite LISP's name) something which CES architectures do: Separating current IP addresses into two independent pieces of reachability and identification information helps to reduce this growth and is called locator/ identifier split (Loc/ID split) [4]. The stable identifier (ID) gives a global name to a node. A changeable locator (Loc) describes how the node can currently be reached through the global Internet. Furthermore, a mapping system (MS) is needed to map locators to identifiers. This principle makes routing in the stable Internet core more scalable because core routing is not affected by changed attachment points and multihoming of edge networks. The deployment of Loc/ID split in the Internet requires modifications to the current routing and addressing architecture. In section 6, there is a further mention of "separation" of "networks" rather than of the scalable "edge" address subset. This is a reference [32] to the 2008 sep./elim. paper and so simply repeats its terminology: The authors of [32] identified two different strategies: separation of core and edge networks and elimination of de-aggregated provider-independent and provider-aggregatable addresses from BGP routing tables. The next paragraph continues: Proposals implementing separation can be subdivided into address rewriting, map-and-encaps, and source routing approaches. I am not sure what the "source routing" "separation" proposals are, but so far this repeats the 2008 paper's taxonomy of considering a proposal which does address rewriting as a "separation" (CES) architecture: both Six/One Router and GSE. But I am sure it is a mistake to characterize GSE as a CES architecture, which is stated two sentences later. The GLI-Split designers state that their architecture was "evolved from the early ideas of GSE". (Quotation below.) They then assert that ILNP and Six/One router are likewise "evolved from the early ideas of GSE". I agree this is the case with ILNP - and Ran states this clearly: http://ilnp.cs.st-andrews.ac.uk/ However, I disagree that Six/One Router "evolved" from GSE. There is no mention of GSE in Christian's paper. While both Six/One Router and GSE involve address rewriting at the borders of EUNs, there are fundamental differences between Six/One Router and any CEE architecture, as listed above. GSE is clearly a CEE architecture and is implementing "Locator/Identifier Separation". Six/One Router is not. The word "separation" only appears in the references of the Six/One Router paper. Likewise "locator". "Identifier" doesn't appear at all. With address rewriting, border routers add global locator information to packets destined for a different domain by coding this information into source and destination addresses for transit purposes. GLI-Split falls into that class. GLI-Split does address rewriting, as does GSE (CEE, but mistakenly classified as a CES architecture) and Six/One Router, which is correctly classified as a CES architecture. But this does not mean that GLI-Split is a CES architecture. It is clearly a CEE architecture. Also Six/One Router [9, 33] uses address rewriting. This is true. Identifiers are only locally routable addresses. This statement appears to be about Six/One Router, but it cannot be true to say this of Six/One Router. The term "Identifier" does not appear in the Six/One Router paper I am quoting from, which I recall is the latest version. The last time we discussed Six/One Router on the RRG was in August 2008, referring to this no-longer existent file: http://users.piuha.net/chvogt/pub/2008/vogt-2008-six-one-router-design.pdf I don't seem to have an electronic copy of this, but Christian announced it on 2008-07-12: http://psg.com/lists/rrg/2008/msg01801.html and the MobiArch08 paper I am quoting from: http://conferences.sigcomm.org/sigcomm/2008/workshops/mobiarch/papers/p13.pdf was last updated on 2008-07-24, so I figure this is the final version. I think it is wrong to state: "Identifiers are only locally routable addresses.". The "edge" addresses used by hosts in Six/One Router networks (which I guess is what the GLI-Split authors were referring to) are indeed only "locally routable" in a direct sense, but they are globally unique, are returned by any DNS query in the world made from within a Six/One Router network. In a sense these addresses are "globally routable" in that packets with these source and destination addresses can be transported to any Six/One Router network in the world, via the writing and rewriting of the upper 64 bits. This in no way makes them "Identifiers" - they are IP addresses and hosts and at least some routers treat them just like IP addresses today: both as Identifiers and Locators. When communicating with nodes in different domains, the addresses are rewritten 1-to-1 through stateless NAT in border routers to globally routable transit addresses. A major focus of Six/One Router is improved multi-homing support. This is all fine. Then there is some discussion of ILNP, which looks fine to me. Then: GLI-Split, ILNP, and Six/One Router have evolved from the early ideas of GSE (global, site, and end-system address elements) [36, 37]. This is true of GLI-Split and ILNP, but not of Six/One Router. It essentially codes a global locator, a local locator, and an identifier into an IPv6 address. Addresses are dynamically combined from these parts. It uses only the identifier for TCP checksum calculation and requires host upgrades for deployment. This is a brief description of GLI-Slit, but it is a mistake to think GSE, ILNP or GLI-Split are Core-Edge Separation architectures. - Robin _______________________________________________ rrg mailing list rrg@irtf.org http://www.irtf.org/mailman/listinfo/rrg