IETF 57 Multu6 WG - Monday morning session - minutes

[Geoff Huston <gih@telstra.net>]

Multi 6 Monday 1300 - 1500

Agenda - overview of submitted drafts

Agenda bashing: none


- - draft-nikander-hip-mm-00.txt, Pekka Nikkander, 5 min


        For background:
        draft-moskowitz-hip-arch-03.txt
        draft-moskowitz-hip-07.txt

  Host Identity Protocol (HIP) has been around for some time. New 
namespace protocol with a history of around 4 years. Today sockets are 
bound to IP addresses, forcing the IP address into a dual role of endpoint 
identifiers and forwarding identifiers. HIP introduces a new namespace 
between the network and transport layers. The sockets are bound to host 
identifiers that are dynamically bound to IP addresses. Hosts are 
identified with public keys, not IP addresses, and apps see only the HIP 
identifiers. The apps need not change is the assertion. Hosts can easily 
have both IPv4 and IPv6 addresses, and the assertion is that end-host 
multi-homing and mobility is trivial. HIP Proxies are described as a kind 
of a hack. HIP may be a part of the multi-homing architecture. 4 
Interoperating implementations, intend to send the drafts to the IESG, and 
more work is needed on mobility and multi-homings with NAT traversal. HIP 
is not a working group but is progressing in the background. HIP is a 
multi-address solution with end-to-end. It solves only one aspect of 
multi6, and has no specific solns for address selection or TE

Matsataka Ohta: You said "HIP Proxy" - do you support multi-proxies for backup
Pekka Nikkander: There is no easy way to have multi HIP proxies in some 
situations, and it does represent a single point of failure



- - draft-coene-sctp-multihome-04.txt, Lode Coene, 15 min


  SCTP approach - endpoints have multiple addresses, where each IP address 
represents a path to a particular endpoint. SCTP is not aware of the level 
of path distinguishing - it would be good if they were, but this is not a 
known property. SCTP can detect path up/down. (Example of host-to-host with 
2 addrs on each host). Multi-homing open up new horizons for SCTP: add and 
remove ip addresses dynamically to the endpoint, that can support mobility. 
Functionality at the endpoint is asserted to be superior to network 
functions in this regards. It does imply that the host requires a routing 
table - not a big deal for a host is the claim. But a big table is required 
for a system with a large connection load. How to maintain the routing 
table is claimed to be implementation dependant (pre-configured or caching 
the INIT). NATs are in the draft because they wanted to warn everyone how 
bad NATs really are! NAT cases for SCTP generates problems that do no 
appear to have straightforward solutions. From the transport level SCTP is 
claimed to be a 'should work' solution.

Lixia Zhang: How about UDP?
Lode Coene: its the same problem, with the application having to undertake 
the selection.
Erik Nordmark: what algorithms have been used in SCTP work to select source 
and destinations? Any write ups of this work?
Lode Coene: none known to me.



- - draft-bagnulo-multi6-mnm-00.txt, Marcelo Bagnulo, 10 min

  Proposes to use MIPv6 to the multi-homing (mh) problem. Example in 
presentation of recovery from current to backup path (Using alternate 
addresses) Both paths have to be bound and identified _before_ an outage 
using binding update messages. The alternate binding will use the Home 
Address Option. Since MIP already needs the exchange of messages along each 
path, this exchange can be used as a path keepalive. The lifetime of the 
binding is limited to 7 minutes, and this is considered to be very short. 
Possible solutions are proposed

Matsataka Ohta: IPv6 has large timeouts for various purposes. If your 
proposal to have the same property so that the new address can be used quickly.
Marcelo Bagnulo: this issue is to build a path outage detection, and we are 
proposed to use the packet exchange for this purpose. The idea is to use 
the same packet format, but change the timing.


- - draft-ohta-e2e-multihoming-05.txt, Masataka Ohta, 20 min

  General introduction on IP and IPv6. References 8+8 Locator and endpoint 
I-D. The proposal is to let end systems have multiple addresses. Let the 
other end select the 'best' address. (The host addresses are part of 
multiple upstream aggregates). The general architecture proposed is to let 
the network inform the host about state to allow the hosts to undertake 
address selection. When should a host attempt alternate addresses? Proposed 
in response to ICMP, routing change, timeouts (TCP only). Proposed that 
applications have an IP (and UDP)-defined packet timeout to trigger 
alternate address use. For very short timeouts it is proposed to send 
multi-copies of the packet with multiple addresses. e-2-e mh and IP 
mobility are similar, although there is mobility timing at the IP layer. 
e2emh has been implemented and running on NetBSD with LIN6, with 
modifications to the stack as described in the presentation. The design 
framework proposed is to make everything optional. Exercising no options is 
single-homed. Use 8+8 Locator/Id separation, with packet reception and 
connection identification determined by the ID. Application to mobility is 
also described. Multiple addresses are supplied to the peer by reverse 
query of DNS using an ID query key followed by a forward query, or carry in 
the TCP header or a new DNS query type. e2e approach is proposed as 
scaleable architecture. MH and mobility are related, and the approach uses 
8+8 separation

Pekka Nikkander: You did not mention security issues in your presentation - 
is this to be addressed later on, or do you have comments now?
Matasaka Ohta: The current Internet is weakly secure. Cookie-based security 
for locator change give only the same level of security.

Peter Werny: What is required in the DNS for this to work?
Matasaka Ohta:  this is different from current V6, as it only uses the 
identifier 8 bytes. In DNS we look up locators of location agents using ID 
of hosts.
Peter Werny: Every host has to have a DNS entry?
Matasaka Ohta:If there is no DNS and not TCP then you are single-homed, and 
you cannot use this mechanisms.
PW: Your draft has no mention of DNS update
Matasaka Ohta: Location is not in the DNS - just the location agent.
Erik Nordmark: Are you assuming a structure for the identifiers?
Matasaka Ohta: It should be reverse lookup-able. Its better to have 
hierarchy in the identifier space, but you can do without hierarchy if you 
use TCP instead of the DNS to pass the multiple addresses



- - draft-ohira-assign-select-e2e-multihome-00.txt, FUJIKAWA Kenji, 5 min

  Each end application can determine a route to use. Applications select a 
route using a selection of a specific source and destination address pair. 
An end application can select a path without full route information is the 
claim. The attributes are claimed to include redundancy and load balancing. 
Modifications to hosts, routers and routing protocols is needed. Site exit 
router selection using source address routing enables redundancy, load 
sharing with multiple paths. Some mechanisms is needed for 'proper' source 
address selection. Transport layer survivability could be an SCTP mechanism 
or other.



- - draft-arifumi-lin6-multihome-api-00.txt, Arifumi Matumoto, 10 min

  Socket API extensions. Propose to use application layer, rather than the 
network. Uses 8+8 model. The API is for manipulation of multiple addresses 
in the application. LIN6 is based on the 8+8 model. LIN6 does address 
acquisition, notification, registration in a secure manner. Hosts identify 
their peer and themselves using only the identifier part. e2e-mh is seen to 
be an application of the LIN6 model. The trigger to switch locators is seen 
to be ICMP-based using host unreachable. APIs need to manipulate locators, 
to make a multi-locator-ready socket, allow API to change locators on the 
fly, and acquire remote locators. The details of API changes described, in 
socket(), getaddrinfo() and getsockopt()/setsocketopt(). APIs are intended 
for active mh applications. UDP requires application support. Future work 
is to put support in to the TCP level, so that no changes are required for 
API for TCP.


- - draft-ohta-multihomed-isps-00.txt, Masataka Ohta, 10 min

  All hosts should have full default-free routing table. This allows 
selector in host to make optimal locator choice, and know when locator is 
unreachable. source address selection for ingress filtering only. The peer 
will not use the source address - it will make its own selection of a 
locator for the peer. Extended example of policy control and filtering.


Pekka Savola: Both of these drafts have been obsoleted
Matasaka Ohta: not a problem!
? (MCI): IF an NLA gets address space from 2 TLAs which does it use?
MO: If gets 2 addresses, as does its customers. The number of prefixes 
cascades down.
? MCI): Scaleaility?
MO: yes, and NLA should be no more than triply homed.
Iljitsch van Beijnum: Why is the information in the routing table superior 
to information you can obtain from the other end?
MO: This does not have scaleability problems if you limit connectivity. 
This is a connectionless system where a host has no information about the 
other end, and the routing table is local information you can use.
Iljitsch van Beijnum: ok, but I disagree with this



- - draft-de-launois-multi6-naros-01.txt, Cedric de Launois, 10 min


  Solution for traffic engineering for mh need sites in a multi-address 
environment. Each host has 1 address per upstream provider. Noted that 
choosing a source address implies choosing a provider (assuming providers 
perform source address filtering). Which source? A host has no information 
about which provider to use to reach a destination. Propose to use a 
dedicated agent (server). A host will query the server with a destination 
address, and the server responds with the source to use. The burden of 
selecting the source address is aggregated to a dedicated server. Note it 
gives only a hint to the host about what address to use. NAROS is not 
intended to preserve flows across address changes. SCTP or HIP could be 
used to preserve flows. The server could be anycast, or undertaken without 
provider interaction. The host / server protocol is a query response packet 
exchange. Where multiple choices exist, multiple parameters can be used to 
make the selection.

Pekka Nikkander: is this a new protocol, or, perhaps, ICMP
Cedric de Launois: No particular protocol - it could be ICMP
PN: There are security issues here, like secure neighbor discovery
Michael Richardson: Takes the example and adds further connections, and 
then adds a policy question about 'acceptable traffic' policies. Can NAROS 
deal with this>
CdL: A lot of requirements could be placed in the NAROS server and it could 
be aware of those kind of requirements.
Matsataka Ohta: Anycast does not include increased robustness for server 
failure. A NAROS server crash will not bring down a anycast route. Also 300 
seconds is too large a value.



- - draft-huitema-multi6-hosts-02.txt, Chistian Huitema & David
   Kessens, 20 min

  Simple multihoming experiment. A problem statement in a bounded example 
environment. A simple network is a single link where multiple hosts see 
multiple boundary routers where each router is connected to distinct 
upstreams. Addresses from providers are mapped to all the hosts. Asserted 
that this is not uncommon in V4 and that the common solution is to NAT the 
local net and allow the NAT to 'rehome' to each outbound. The consequence 
is flow breakage across the rehoming of the NAT. The bounds are that the 
ISPS do not exchange information, there are provider addresses with an 
assigned prefix per provider. Hosts configure an address with each prefix. 
Need to resolve host choice of egress router selection (as a function of 
the source address)

Erik Nordmark:  There are people talking about movement detection, and this 
gets all routers to advertise all prefixes
Christian Huitema: Thats not incompatible - several routers can advertise 
the same information, provided that the information is equivalent, and the 
routers can handle all such packets.
Pekka Savola: please clarify the applicability. This is only the case where 
hosts are directly connected to all egress routers.
Christian: this is a common case.
MO: You don't need tunnels in a single link network. In a multi-link 
network you need tunnels.
CH: This does nothing for MTU discovery. For single link there is a very 
simple solution and this can be extended for multi-links
MO: Ands I'm saying its impossible
CH: fine!

  No need for tunnels in a single link network, and the routers can pass 
off to each other in the event of dynamic failure. The assertion is that in 
a single link network this requirement can be easily met. Dead exist 
routers or dead ISP require some consideration. If the exit router knows 
that the path is dead it can send a poison advertisement of the prefix. The 
real issue with this form of mh is a very soft definition of 'broken' where 
the link may be up, but the path to the remote end point may be unuseable. 
This kind of problem is an e2e detection issue. Hosts may need to keep 
track of connections and track quality. If you know an ingress path is dead 
do you need to update the DNS to remove the dead prefix from your host 
entry? Of course you may not know and in this case your peer will need to 
work out what address to use. Maintenance of TCP connections is an issue. 
MIP6 may be an answer, or SCTP for 'new hosts'. For 'old' hosts, he 
connection will fail, and needs to be reestablished. Exit / entrance 
selection is also an issue. One approach is to only advertise the preferred 
address in the DNS if you have a primary / backup scenario. And in a 1 + 1 
scenario, then advertise both. On the outgoing the solution may be a local 
server to assist, or to document preferences in the routers. We appear to 
be able to design solutions that require changes to the IPv6 standards, do 
no require address rewriting at exit points, but it could work,

Pekka Nikkander: New hosts can use MIPv6 or SCTP. IN MIPv6 don't you need 
to change both ends?
CH: The support for the connected node in MIPv6 is supposed to be 
implemented everywhere.
PN: You need to change the address in both ends.
CH: The time appears to be around 5 or 6 minutes.
PN: If you are going to change the code at both ends then you should try 
HIP in your experiments as well.
CH: You are free to experiment with HIP
Fujikawa: It seems like an application cannot select different path from 
other applications in a host?
CH: No, not so. The host has several IPv6 addresses. An application that 
want to do path selection can bind to a source address and connect to a 
destination and select a path.
Matasaka Ohta: It is stupid to keep using a complication MIPv6
CH: Complexity is management of the Home agent and security functions to 
certain classes of attacks and you will need  to have some form of security 
in any case.
Matasaka Ohta: This only works in a single link case.

  In a larger site the problem is ingress filtering, because its harder to 
do source-based routing. The simple solution is to work with the ISP to 
lift source filters. Even larger sites have their own PI space and AS#.

IvB: Disable ingress filtering can be down for the local upstream, but the 
chain may extend upward
CH: ingress filtering in the middle of the Internet is a bad idea
MO: what will you do with a large site?
CH: lets call them medium
Bob Hinden: ISPs would be more amenable to break ingress filtering than 
route specifics.
?: Ingress filtering should not be an issues.
Mat Ford: Define a large site?
CH: establish a registry relationship!


- - draft-savola-multi6-asn-pi-00.txt, Pekka Savola, 10 min


  Claimed that this is not the best solution in all cases, but better than 
some others. Need to avoid the routing mess of advertising more specific 
and need solutions soon. Approach to use the AS number to create PI space 
for larger enterprises. e.g. 2000:<ASN>::/32. Issues about 16 / 32 bit AS 
numbers, and a claim that 32 bit AS numbers would indicate a RIR policy 
failure.



Moshens VC(?): How do you get uniqueness of the prefix
PS: This is 2000 - it won't collide!
MO: There are already too many ASes deployed
Geoff Huston: You are assuming AS remain at 16bits. What happens when AS 
drain in 2011. and we move to 32 bit AS numbers? This is a relatively short 
term solution with a visible drop dead point - right?
PV: yes.
?: This is good solution
PV: an appendix shows how to deal with 32 bit AS numbers, but I don't lkike 
this solution.
Tim Chen: This cuts out the smaller sites that do not have ASs.
Randy Bush: Why reluctant to give out ASes to routing domains who's policy 
domains are different from their neighbors?


- - draft-van-beijnum-multi6-isp-int-aggr-01.txt, Iljitsch van Beijnum,
   15 min


  Geographical aggregation. Admitted that topology is not correlated to 
geography, and even if the geo part doesn't work there are still some savings.

MH: This gives little actual aggregation
?: Asymmetrical routes break in your model
IvB: Routing is asymmetrical in multi-homing in any case.
Tony Hain: Aggregatibility is the question. The concept appears fine, but 
you are making assumptions about aggregation boundaries here.