NEMO Multi-homing Issues
Prepared for 56th IETF NEMO WG
By
Ng Chan Wah & Takeshi Tanaka
19 03 2003
56th IETF – NEMO Working Group
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Deployment Scenarios (1/4)
 Multiple Egress Interfaces, Single HA
Binding Cache
HoA
CoA
1::1
2::1
1::2
3::1
HA
Routing Table
Dest
Next Hop
1:1::/96
1::1
Internet
802.11 Interface
CoA=2::1, HoA=1::1
MR
GPRS Interface
CoA=3::1, HoA=1::2
Prefix=1:1::/96
MNN-1
Addr=1:1::1
MNN-2
Addr=1:1::2
56th IETF – NEMO Working Group
2
Deployment Scenarios (2/4)
 Multiple Egress Interfaces, Different HAs
Binding Cache
HoA
CoA
1::1
3::1
Binding Cache
HA-2
HA-1
Next Hop
1:1::/96
1::1
CoA
2::1
4::1
Routing Table
Routing Table
Dest
HoA
Internet
802.11 Interface
CoA=3::1, HoA=1::1
MR
Dest
Next Hop
2:1::/96
2::1
GPRS Interface
CoA=4::1, HoA=2::1
Prefix=1:1::/96, 2:1::/96
Addr=1:1::1
Or 2:1::1
MNN-1
MNN-2
56th IETF – NEMO Working Group
Addr=1:1::2
Or 2:1::2
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Deployment Scenarios (3/4)
 Multiple MRs, Single HA
Binding Cache
HoA
CoA
1::1
2::1
1::2
3::1
HA
Routing Table
Dest
Next Hop
1:1::/96
???
Internet
CoA=2::1
HoA=1::1
CoA=3::1
HoA=1::2
MR-1
MR-2
Prefix=1:1::/96
Addr=1:1::1
MNN-1
Prefix=1:1::/96
MNN-2
56th IETF – NEMO Working Group
Addr=1:1::2
4
Deployment Scenarios (4/4)
 Multiple MRs, Different HAs
Binding Cache
HoA
CoA
1::1
3::1
Binding Cache
HA-1
HA-2
Next Hop
1:1::/96
1::1
Internet
CoA=3::1
HoA=1::1
CoA=4::1
HoA=2::1
MR-1
MR-2
Prefix=1:1::/96
Addr=1:1::1
Or 2:1::1
CoA
2::1
4::1
Routing Table
Routing Table
Dest
HoA
MNN-1
Dest
Next Hop
2:1::/96
2::1
Prefix=2:1::/96
MNN-2
56th IETF – NEMO Working Group
Addr=1:1::2
Or 2:1::2
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Issues
 When MR detects a failed egress link, how can
NEMO recover?
 As per IPv6:
• Nothing much
• send ICMP dest unreachable
• wait for possible recovery by dynamic routing protocol
 But this is undesired for NEMO with multiple
egress links
 Should NEMO try to incorporate mechanism that
allows faster recovery?
 Considering that we expect link failures to occur far
more frequently in NEMO
56th IETF – NEMO Working Group
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Possible Approach (1/2)
 MR dynamically
change its tunnel entry
interface when its
egress link fails
 MR need to detect the
presence of other MRs
having alternate routes
in its local network
 possibility: listen for
RA with LifeTime!=0
HA-1
HA-2
Internet
MR-1
MR-2
RA(LifeTime!=0)
MNN-1
56th IETF – NEMO Working Group
MNN-2
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Possible Approach (2/2)
 Obtain CoA from
other MRs when its
egress link fails
 Re-establish bidirectional tunnel using
this new CoA
 Issues:
 Possible looping when
both MRs’ egress link
fails
HA-1
HA-2
Internet
X
MR-1
Obtain
CoA
MR-2
Re-establish tunnel
MNN-1
56th IETF – NEMO Working Group
MNN-2
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Mailing List - Resolved
 Requirements Draft
 issue raised on multiple addresses configure to
single interface (mentioned in the terminology
draft)
 similar issues when home link is multi-homed
 consensus:
• Non-NEMO specific
• Should not be worked on
56th IETF – NEMO Working Group
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Mailing List - Unresolved
 Requirements R13
 R12: The solution MUST function for multi-homed mobile
networks.
• R13.1: The solution MUST support mobile networks with multiple
MRs. In particular, if the path through one MR becomes unavailable,
the solution MUST be able to establish new communications between
MNNs and CNs using an alternative available path through another
MR. Additionally, if the path through one MR becomes unavailable,
the solution SHOULD (or MAY?) preserve established
communications by re-routing the packets of such communication
through an alternative available MR.
• R13.2: The solution MUST support MR with multiple interfaces. In
particular, if the path through one of the MR interfaces becomes
unavailable, the solution MUST be able to establish new
communications between MNNs and CNs using an alternative
available interface of the MR. Additionally, if the path through one
MR interfaces becomes unavailable, the solution MUST (or
SHOULD?) preserve established communications by coursing
packets of such communication through an alternative available
interface of the MR
56th IETF – NEMO Working Group
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Mailing List - Unresolved
 Requirements R13
 Change to
• NEMO solution SHOULD not prevent the use of
any form of multi-homing
56th IETF – NEMO Working Group
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Mailing List - Unresolved
 Issue of multiple MR, different HA, advertising
same prefixes
 requires co-ordination between HA
 Issue of multiple MR, different HA, advertising
different prefixes
 does not matter which prefix LMN choose to use, it
can send packet to any MR as next hop router
 however, also requires co-ordination between HA
 Is NEMO WG working on a solution for such
cases?
56th IETF – NEMO Working Group
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Mailing List – Unresolved
 Issue on MR with multiple egress interface,
single HA
 argument that we cannot have a single HoA
assigned to both egress interface and active at
the same time, since a single HoA cannot be
bound to two (or more) CoAs simultaneously
 possibility of multiple CoAs bound to same
HoA
• Draft-wakikawa-mipv6-multiplecoa-00.txt
56th IETF – NEMO Working Group
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