[Nfd-dev] Help needed with debugging duplicate Nonce

Ashlesh Gawande (agawande) agawande at memphis.edu
Mon Jun 27 11:04:00 PDT 2016


Hi all


I was running a simple three node topology in Mini-NDN (no experiment, simply: sudo minindn topology_file):

                          a
                        /     \
                 10 /        \ 10
                     /           \
                    b----------c
                          10

a-eth0 (1.0.0.1)-b-eth0(1.0.0.2)
a-eth1(1.0.0.5)-c-eth0(1.0.0.6)
b-eth1(1.0.0.9)-c-eth1(1.0.0.10)

I have attached the topology file used.

ndn-cxx commit:  67cb75c7d8a61981cf21581702c955cc7d170642
NFD commit: 891f47bcfad45885408d1956657be5612620a12d
NLSR commit: af909fcc138ce18bd433edecc248ed2b60fc9737
ndn-tools commit: d2300731edd88593290ac0c33ed25d5b353b6634

I started tcpdump before NLSR starts on each node and then grepped for NACKs (all of them are duplicate NACKs).

Then I followed a particular Nonce (at random) to see how the duplicate NACK was generated:

Tcpdumps are attached in pcap format.
I just used ndndump -r to dump them to ndndump* files and grepped:

tmp$ grep --color=always 355693607 ndndump.* | sort -t: -k2
ndndump.c-eth1_1.0.0.6:1467048841.203507 From: 1.0.0.6, To: 1.0.0.5, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.a-eth1_1.0.0.5:1467048841.203512 From: 1.0.0.6, To: 1.0.0.5, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.c-eth0_1.0.0.10:1467048841.203513 From: 1.0.0.10, To: 1.0.0.9, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.b-eth1_1.0.0.9:1467048841.203514 From: 1.0.0.10, To: 1.0.0.9, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.b-eth0_1.0.0.2:1467048841.213733 From: 1.0.0.2, To: 1.0.0.1, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.a-eth0_1.0.0.1:1467048841.213740 From: 1.0.0.2, To: 1.0.0.1, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.a-eth0_1.0.0.1:1467048841.214191 From: 1.0.0.1, To: 1.0.0.2, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.b-eth0_1.0.0.2:1467048841.214191 From: 1.0.0.1, To: 1.0.0.2, Tunnel Type: UDP, INTEREST: /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.a-eth0_1.0.0.1:1467048841.224056 From: 1.0.0.1, To: 1.0.0.2, Tunnel Type: UDP, NACK: Duplicate, /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.b-eth0_1.0.0.2:1467048841.224078 From: 1.0.0.1, To: 1.0.0.2, Tunnel Type: UDP, NACK: Duplicate, /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.a-eth0_1.0.0.1:1467048841.224360 From: 1.0.0.2, To: 1.0.0.1, Tunnel Type: UDP, NACK: Duplicate, /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607
ndndump.b-eth0_1.0.0.2:1467048841.224360 From: 1.0.0.2, To: 1.0.0.1, Tunnel Type: UDP, NACK: Duplicate, /ndn/NLSR/sync/d34157d84d19a4f39c359c9794b2686cc061a7dc2411a44255c50a173c1cc89e?ndn.MustBeFresh=1&ndn.Nonce=355693607

Seems like:
1) c sends interest to a
2) c sends same interest to b
3) b sends same interest to a
4) a sends same interest to b
5) a sends NACK [Duplicate] to b
6) b sends NACK [Duplicate] to a

Strategy is set as follows by NLSR:
mininet> a nfd-status -s
Strategy choices:
  / strategy=/localhost/nfd/strategy/best-route/%FD%04
  /ndn/NLSR/sync strategy=/localhost/nfd/strategy/multicast/%FD%01
  /localhost strategy=/localhost/nfd/strategy/multicast/%FD%01
  /ndn/broadcast strategy=/localhost/nfd/strategy/multicast/%FD%01
  /ndn/NLSR/LSA strategy=/localhost/nfd/strategy/multicast/%FD%01
  /ndn/broadcast/KEYS strategy=/localhost/nfd/strategy/multicast/%FD%01
  /localhost/nfd strategy=/localhost/nfd/strategy/best-route/%FD%04

So are these duplicate NACKs expected behavior?

Thanks
Ashlesh


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