1. End-to-end Multihoming <draft-ohta-e2e-multihoming-00.txt>
Masataka Ohta

2. THE PROBLEM Full Routing Table Too Large
because of random IPv4 address allocation
to be solved with IPv6
because of Multihoming
# of TLAs should be controlled
below what?
below 1,000 seems to be easy
below 100 is not difficult, hopefully

3. TLI
SLI
Subscribers
Typical Scenario of IPv6 Multihoming

4. 1 1 1 1 1
TLI 2 3 3 2 2
SLI 5 3 8 2 4
Subscribers
Number of Prefixes with E2E Multihoming

5. Multihoming Typical IPv4 multihoming
Advertise an address range through multiple (not necessarily 2) routes
Explosion of
# of routing table entries
# of ASes

6. Rest of the Internet
ISP A
ISP B
Multihomed
Site
Singly Homed
Site H

7. Multihoming by (Intelligent) Routing
Rest of the Internet
１３１．１１２．０．０／１６、
１３１．１１３．０．０／１６
１３１．１１２．０．０／１６
ISP A
ISP B
１３１．１１３．０．０／１６
１３１．１１２．０．０／１６
１３１．１１２．０．０／１６
Multihomed
Site
Singly Homed
Site H
Multihoming by (Intelligent) Routing

8. Multihoming by (Intelligent) Routing
Rest of the Internet
１３１．１１２．０．０／１5
１３１．１１２．０．０／１６
ISP A
ISP B
１３１．１１３．０．０／１６
１３１．１１２．０．０／１６
１３１．１１２．０．０／１６
Multihomed
Site
Singly Homed
Site H
Multihoming by (Intelligent) Routing

9. End to End Multihoming (1)
A host has multiple addresses
Application or transport tries all the destination addresses
Each address range can be aggregated
No routing table entry explosion
No AS number explosion

10. End to End Multihoming (2)
When to Try Alternative Addresses?
Application/Transport dependent
Controlled by the intelligence of end systems
TCP will have a default timeout period
Which Address Should be Tried Next?
Routing table can give hints
Lack of a routing table entry means lack of reachability to a host
Existence of an aggregated routing table entry does not mean reachability to the host
Metric information in routing table can help too

11. Rest of the Internet ISP A ISP B Multihomed Site Singly Homed Site H
１３１．０．０．０／８
１３３．０．０．０／８
ISP A
ISP B
１３１．１１３．０．０／１６
１３１．１１２．０．０／１６
１３３．１１２．０．０／１６
Multihomed
Site
Singly Homed
Site H
１３３．１１２．３２．１３２，
１３１．１１２．３２．１３２
End to End Multihoming

12. Because It IS End to End No change to router functionality
MUST change API on hosts
Or the hosts are singly homed
Wrong to assume
Intelligent routers help dumb nodes
A host can and is recommended to have a default free global (but now small) routing table
A real dumb host is dumb and singly homed

13. Do Intelligent End Systems Require Standard IGP?
No.
Standard protocol to distribute (but not compute) routing table to hosts is required
RIPv2 (with metric >15) seems to be good enough. Or RA?
BGP routers generate metric from policy based preference

14. Source Address Selection?
Wrong topic for multihoming
Both sources select destination addresses
At the destination, reverse & forward DNS lookup of source address gives all the address of the source
The destination selects an appropriate destination address for reply
No source address selection by source meaningful
Or, protocols may be modified to carry them

15. TCP API/Protocol Changes
Source have no reachability information of SYNACK reply addresses at the destination
Destination should select the address
Multiple PCB entries for a connection
How to give the multiple addresses of the source to the destination?
DNS?
Let SYN carry all the addresses?

16. DNS Changes DNS can not give addresses for DNS reply
Clients should choose source address reachable from the name server
First, choose randomly
Should (re)try with other source addresses
A lot of delay
Or, change protocol?
Query carries all the addresses of the source

17. End to End Multihoming and DNS/SMTP
DNS and SMTP servers already deploy E2E multihoming
NS/MX servers may have multiple A records
If a server has multiple addresses
All the addresses are tried
It is of course as the most important, required-to-be-rubust applications of the Internet

18. 8+8 DNS reverse lookup by lower 8 bytes only
Hosts are identified by lower 8 bytes (IID)
A compact DNS name carried by all the packets of all the protocols
Makes modification to application/transport protocols for E2E multihoming easier
Not Mike O’dell’s GSE one (violate E2E)
Teraoka san will present his version (8+5)