2012年12月20日にあった JANOG Softwire WG Interim Meeting での発表資料です。

1. ASAMAP Update
浅間 正和 @ 有限会社 銀座堂

2. Maximum IPv6 packet size
• Encapsulation/Translation 後の IPv6 packet の maximum
size が 1280 byte 固定でしたが以下の command で変
更できるようになりました
•
# set
interfaces map map0 ipv6-fragment-size 1500
• 未設定時の default 値は 1280 です

3. Fragment inner IPv4 packet
• Encapsulation の時 IPv6 stack で fragment する方法しか
利用できませんでしたが以下の command で IPv4
stack で fragment するか IPv6 stack で fragment するか
を選択できるようになりました
•
# set
interfaces map map0 ipv4-fragment-inner true
• true を指定すると IPv4 stack で fragment します
• false を指定すると IPv6 stack で fragment します
• 未設定時の default 値は true です

4. IPv4 Header IPv4 Header
Fragment inner IPv4 packet
20 byte 20 byte
(offset 1472) (offset 0)
8 byte UDP Header
DATA
1500 byte
528 byte
(1473 2000)
DATA
1472 byte
(1 1472)
40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header
IPv4 Header IPv4 Header IPv4 Header IPv4 Header IPv4 Header
20 byte 20 byte 20 byte 20 byte 20 byte
(offset 1432) (offset 0) (offset 1472) (offset 1432) (offset 0)
DATA
1460 byte
1460 byte
DATA 8 byte UDP Header DATA 40 byte 8 byte UDP Header
568 byte 528 byte (1433 1472)
(1433 2000) (1473 2000)
DATA DATA
1432 byte 1432 byte
(1 1432) (1 1432)
40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header
IPv6 Frag Hdr IPv6 Frag Hdr IPv4 Header IPv6 Frag Hdr IPv6 Frag Hdr
8 byte 8 byte 20 byte 8 byte 8 byte
(offset 1232) (offset 0) (offset 1472) (offset 1232) (offset 0)
IPv4 Header IPv4 Header
1280 byte
1280 byte
DATA 20 byte DATA DATA 20 byte
796 byte (offset 0) 528 byte 268 byte (offset 0)
(1205 2000) (1473 2000) (1205 1472)
8 byte UDP Header 8 byte UDP Header
1204 byte
DATA
(1 1204)
←これにしてます。 1204 byte
DATA
(1 1204)

5. IPv4 Header IPv4 Header
Fragment inner IPv4 packet
20 byte 20 byte
(offset 1472) (offset 0)
8 byte UDP Header
DATA
1500 byte
528 byte
(1473 2000)
DATA
1472 byte
(1 1472)
40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header
IPv4 Header IPv4 Header IPv4 Header IPv4 Header IPv4 Header
20 byte 20 byte 20 byte 20 byte 20 byte
(offset 1432) (offset 0) (offset 1472) (offset 1432) (offset 0)
DATA
1460 byte
1460 byte
DATA 8 byte UDP Header DATA 40 byte 8 byte UDP Header
568 byte 528 byte (1433 1472)
(1433 2000) (1473 2000)
DATA DATA
1432 byte 1432 byte
(1 1432) (1 1432)
40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header 40 byte IPv6 Header
IPv6 Frag Hdr IPv6 Frag Hdr IPv4 Header IPv6 Frag Hdr IPv6 Frag Hdr
8 byte 8 byte 20 byte 8 byte 8 byte
(offset 1232) (offset 0) (offset 1472) (offset 1232) (offset 0)
IPv4 Header IPv4 Header
1280 byte
1280 byte
DATA 20 byte DATA DATA 20 byte
796 byte (offset 0) 528 byte 268 byte (offset 0)
(1205 2000) (1473 2000) (1205 1472)
8 byte UDP Header 8 byte UDP Header
1204 byte
DATA
←この中から 1204 byte
DATA
選べます。
(1 1204) (1 1204)

6. Fragment inner IPv4 packet
• ipv4-fragment-inner false の時の例
13:21:41.890828 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1: frag (0|1232)
IP truncated-ip - 796 bytes missing! 172.16.1.0 > 10.1.1.11:
ICMP echo request, id 10382, seq 4, length 2008
13:21:41.890862 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1: frag (1232|796)
13:21:41.891638 IP6 2001:db8::1 > 2001:db8:100:0:ac:1001:0:8800: frag (0|1232)
IP truncated-ip - 796 bytes missing! 10.1.1.11 > 172.16.1.0:
ICMP echo reply, id 10382, seq 4, length 2008
13:21:41.891658 IP6 2001:db8::1 > 2001:db8:100:0:ac:1001:0:8800: frag (1232|796)
• ipv4-fragment-inner true の時の例
13:17:58.244688 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1:
IP 172.16.1.0 > 10.1.1.11: ICMP echo request, id 47244, seq 32, length 1216
13:17:58.245059 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1:
IP 172.16.1.0 > 10.1.1.11: icmp
13:17:58.247150 IP6 2001:db8::1 > 2001:db8:100:0:ac:1001:0:8800:
IP 10.1.1.11 > 172.16.1.0: ICMP echo reply, id 47244, seq 32, length 1216
13:17:58.247175 IP6 2001:db8::1 > 2001:db8:100:0:ac:1001:0:8800:
IP 10.1.1.11 > 172.16.1.0: icmp

7. Path MTU discovery
• ICMPv6 packet too big を受け取った際に埋め込まれ
た MTU 値を pMTU として設定するようにしました
13:26:07.303972 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1:
IP 172.16.1.0 > 10.1.1.11: ICMP echo request, id 55433, seq 2, length 1440
13:26:07.304019 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1:
IP 172.16.1.0 > 10.1.1.11: icmp
13:26:07.304926 IP6 2001:db8:ffff:ffff::1 > 2001:db8:100:0:ac:1001:0:8800:
ICMP6, packet too big, mtu 1280, length 1240
13:26:08.310210 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1:
IP 172.16.1.0 > 10.1.1.11: ICMP echo request, id 55433, seq 3, length 1216
13:26:08.310597 IP6 2001:db8:100:0:ac:1001:0:8800 > 2001:db8::1:
IP 172.16.1.0 > 10.1.1.11: icmp
13:26:08.311739 IP6 2001:db8::1 > 2001:db8:100:0:ac:1001:0:8800:
IP 10.1.1.11 > 172.16.1.0: ICMP echo reply, id 55433, seq 3, length 1216
13:26:08.311758 IP6 2001:db8::1 > 2001:db8:100:0:ac:1001:0:8800:
IP 10.1.1.11 > 172.16.1.0: icmp

8. MAP 1:1
5.2. Basic mapping rule (BMR)
| n bits | o bits | s bits | 128-n-o-s bits |
+--------------------+-----------+---------+------------+----------+
| Rule IPv6 prefix | EA bits |subnet ID| interface ID |
+--------------------+-----------+---------+-----------------------+
|<--- End-user IPv6 prefix --->|
Figure 3: IPv6 address format
... snip ...
Shared IPv4 address:
| r bits | p bits | | q bits |
+-------------+---------------------+ +------------+
| Rule IPv4 | IPv4 Address suffix | |Port-Set ID |
+-------------+---------------------+ +------------+
| 32 bits |
Figure 4: Shared IPv4 address
... snip ...
The length of r MAY be 32, with no part of the IPv4 address embedded
in the EA bits. This results in a mapping with no dependence between
the IPv4 address and the IPv6 address. In addition the length of o
MAY be zero (no EA bits embedded in the End-User IPv6 prefix),
meaning that also the PSID is provisioned using e.g. the DHCP option.

9. MAP 1:1
Rule IPv6 prefix
EA bits
Rule IPv4 prefix PSID
Rule IPv6 prefix
EA
bits
Rule IPv4 prefix PSID
↑ Rule PSID prefix？

10. MAP 1:1
• Rule IPv4 prefix が /32 の時に限り Rule PSID prefix と
して PSID の一部を設定出来るようにしました
• その上で EA bits length が 0 の場合は MAP 1:1 として
利用することができます
# set interfaces map map0 rule 1 ipv6-prefix 2001:db8:1234::/48
# set interfaces map map0 rule 1 ipv4-prefix 192.0.2.18/32
# set interfaces map map0 rule 1 psid-prefix 0x34/8
# set interfaces map map0 rule 1 ea-length 0
# set interfaces map map0 rule 2 ipv6-prefix 2001:db8:5678::/48
# set interfaces map map0 rule 2 ipv4-prefix 192.0.2.18/32
# set interfaces map map0 rule 2 psid-prefix 0x56/8
# set interfaces map map0 rule 2 ea-length 0
# set interfaces map map0 rule 3 ...

11. MAP 1:1
struct map_rule *
map_rule_find_by_ipv6addr(struct map *m, struct in6_addr *ipv6addr)
{
struct map_rule *mr = NULL, *tmp;
read_lock(&m->rule_lock);
list_for_each_entry (tmp, &m->rule_list, list) {
if (ipv6_prefix_equal(&tmp->p.ipv6_prefix, ipv6addr,
tmp->p.ipv6_prefix_length)) {
if (!mr || (tmp->p.ipv6_prefix_length >
mr->p.ipv6_prefix_length))
mr = tmp;
}
}
read_unlock(&m->rule_lock);
return mr;
}
n 個の Mapping Rule に対して
O(n) の計算量！！！

12. IPv6 → IPv4 pps 64 byte packet
1,200kpps
1,000kpps
800kpps
600kpps
400kpps
200kpps
0kpps
1 16 256 4096
Installed Mapping Rules

13. Radix tree for IPv6 addr. and IPv4 addr. + PSID
• IPv6 → IPv4 変換時の探索用に Rule IPv6 prefix から、
IPv4 → IPv6 変換時の探索用に Rule IPv4 prefix と Rule
PSID prefix から、それぞれ Radix tree を生成するこ
とで Mapping Rule の探索を高速化しました
Mapping Rule の数に依らず
O(k) の計算量！！！
※ IPv6 addr. からの探索の場合:
k = max(Rule IPv6 prefix length)
※ IPv4 addr. + port num. からの探索の場合:
k = max(Rule IPv4 prefix length + Rule PSID prefix length)

14. List Tree
IPv6 → IPv4 pps 64 byte packet
1,200kpps
1,000kpps
800kpps
600kpps
400kpps
200kpps
0kpps
1 16 256 4096
Installed Mapping Rules

15. List Tree
IPv6 → IPv4 pps 64 byte packet
1,200kpps
1,000kpps
800kpps
600kpps
400kpps
200kpps
0kpps
1 16 256 4096
Installed Mapping Rules

16. List Tree
IPv4 → IPv6 pps 64 byte packet
1,200kpps
1,000kpps
800kpps
600kpps
400kpps
200kpps
0kpps
1 16 256 4096
Installed Mapping Rules

17. List Tree
IPv6 → IPv4 bps 1478 byte packet
10,000Mbps
9,000Mbps
8,000Mbps
7,000Mbps
6,000Mbps
5,000Mbps
4,000Mbps
3,000Mbps
2,000Mbps
1,000Mbps
0Mbps
1 16 256 4096
Installed Mapping Rules

18. List Tree
IPv4 → IPv6 bps 1478 byte packet
10,000Mbps
9,000Mbps
8,000Mbps
7,000Mbps
6,000Mbps
5,000Mbps
4,000Mbps
3,000Mbps
2,000Mbps
1,000Mbps
0Mbps
1 16 256 4096
Installed Mapping Rules

19. PSID et cetera
• こんなときどうする？
# set interfaces map map0 rule 1 ea-length 0
# set interfaces map map0 rule 1 ipv4-prefix 192.0.2.18/32
# set interfaces map map0 rule 1 ipv6-prefix 2001:db8:100::/64
# set interfaces map map0 rule 1 psid 0x23
# set interfaces map map0 rule 1 psid-length 8
# set interfaces map map0 rule 1 psid-offset 4
# set interfaces map map0 rule 2 ea-length 0
# set interfaces map map0 rule 2 ipv4-prefix 192.0.2.18/32
# set interfaces map map0 rule 2 ipv6-prefix 2001:db8:200::/64
# set interfaces map map0 rule 2 psid 0x234
# set interfaces map map0 rule 2 psid-length 12
# set interfaces map map0 rule 2 psid-offset 4
• 現状は psid-length の長いものが採用される
• 明らかに miss configuration 状態なので rule 2 を reject
すべき？

20. PSID et cetera
• こんなときどうする？
# set interfaces map map0 rule 1 ea-length 0
# set interfaces map map0 rule 1 ipv4-prefix 192.0.2.18/32
# set interfaces map map0 rule 1 ipv6-prefix 2001:db8:100::/64
# set interfaces map map0 rule 1 psid 0x12
# set interfaces map map0 rule 1 psid-length 8
# set interfaces map map0 rule 1 psid-offset 0
# set interfaces map map0 rule 2 ea-length 0
# set interfaces map map0 rule 2 ipv4-prefix 192.0.2.18/32
# set interfaces map map0 rule 2 ipv6-prefix 2001:db8:200::/64
# set interfaces map map0 rule 2 psid 0x23
# set interfaces map map0 rule 2 psid-length 8
# set interfaces map map0 rule 2 psid-offset 4
• 現状は psid-offset の小さいものが採用される
• 明らかに miss configuration 状態なので rule 2 を reject
すべき？

21. PSID et cetera
PSID offset # of Mapping Rule 192.0.2.18:0x12/40
0 1
1 0 192.0.2.18:0x0/34
: :
4 4 192.0.2.18:0x34/40
: :
16 0 192.0.2.18/32
192.0.2.18:0x89/40
192.0.2.0/24 192.0.2.18:0x8/34
192.0.2.18:0xab/40
192.0.2.137/32
192.0.0.0/16
192.0.137.0/24 Node w/ Mapping Rule
Node w/o Mapping Rule

22. まとめ？
• Encapsulation/Translation 後の IPv6 packet の maximum
size の変更に対応しました
• IPv4 stack での fragment に対応しました
• Path MTU discovery に対応しました
• MAP 1:1 に対応しました
• 質問
☞ Path MTU discovery は実施すべき？
☞ MAP 1:1 どうします？ PSID の重複対策は？
☞ PSID offset って Mapping Rule 毎に必要？

24. List 1-Rules List 16-Rules List 256-Rules List 4096-Rules
Tree 1-Rules Tree 16-Rules Tree 256-Rules Tree 4096-Rules
IPv4 → IPv6 bps
5,000Mbps
4,500Mbps
4,000Mbps
3,500Mbps
3,000Mbps
2,500Mbps
2,000Mbps
1,500Mbps
1,000Mbps
500Mbps
0Mbps
64 128 256 512 1024 1280 1472
IPv4 Packet Size [byte]

25. List 1-Rules List 16-Rules List 256-Rules List 4096-Rules
Tree 1-Rules Tree 16-Rules Tree 256-Rules Tree 4096-Rules
IPv6 → IPv4 bps
10,000Mbps
9,000Mbps
8,000Mbps
7,000Mbps
6,000Mbps
5,000Mbps
4,000Mbps
3,000Mbps
2,000Mbps
1,000Mbps
0Mbps
64 128 256 512 1024 1280 1472
IPv4 Packet Size [byte]

26. List Tree
IPv4 → IPv6 bps 1478 byte packet
10,000Mbps
9,000Mbps
8,000Mbps
7,000Mbps
6,000Mbps
5,000Mbps
4,000Mbps
3,000Mbps
2,000Mbps
1,000Mbps
0Mbps
1 16 256 4096
Installed Mapping Rules

27. List Tree
IPv6 → IPv4 bps 1478 byte packet
10,000Mbps
9,000Mbps
8,000Mbps
7,000Mbps
6,000Mbps
5,000Mbps
4,000Mbps
3,000Mbps
2,000Mbps
1,000Mbps
0Mbps
1 16 256 4096
Installed Mapping Rules

28. List 1-Rules List 16-Rules List 256-Rules List 4096-Rules
Tree 1-Rules Tree 16-Rules Tree 256-Rules Tree 4096-Rules
IPv4 → IPv6 pps
400kpps
350kpps
300kpps
250kpps
200kpps
150kpps
100kpps
50kpps
0kpps
64 128 256 512 1024 1280 1472
IPv4 Packet Size [byte]

29. List 1-Rules List 16-Rules List 256-Rules List 4096-Rules
Tree 1-Rules Tree 16-Rules Tree 256-Rules Tree 4096-Rules
IPv6 → IPv4 pps
1,500kpps
1,250kpps
1,000kpps
750kpps
500kpps
250kpps
0kpps
64 128 256 512 1024 1280 1472
IPv4 Packet Size [byte]

30. List Tree
IPv4 → IPv6 pps 64 byte packet
1,200kpps
1,000kpps
800kpps
600kpps
400kpps
200kpps
0kpps
1 16 256 4096
Installed Mapping Rules

31. List Tree
IPv6 → IPv4 pps 64 byte packet
1,200kpps
1,000kpps
800kpps
600kpps
400kpps
200kpps
0kpps
1 16 256 4096
Installed Mapping Rules