1

Network Layer

- IP (Internet Protocol) -

2

IP(Internet Protocol) ～ Functions and Features ～

• Functions – Identify the Interface

• 32bits(or 128bits) ID

• IP address for interface

– IP packet forwarding • Exchange IP packets

• Router determines route

– Fragmentation if IP packet • Too large packet must be

fragmented

• Re-fragmented at the destination

• Features

– Best-Effort delivery • Datagram /connectionless

• Excuse if not be delivered

• Stateless for connection

– Scale-free • Against the number of data

flows

• Recursive routing configuration

– Open technical spec. • RFC791

3

Routing the IP Packet

Net1

Net2

Net3

Net4

Net1 R1 Net2 R1 Net3 R2 Net4 R3

Routing Table

Router R1

R2

R3

• Router resolves the appropriate neighbor node, that the received IP packet should be forwarded to lead to the destination interface.

東京駅 Car Train Bike Foot

成田

羽田

新横浜駅

太平洋線

欧州線

国内線

新幹線

4

Router processes IP functions

• IP packet (= human-being)

• IP at core, and TCP at the edges

IP TCP APP

IP IP TCP APP

net-A net-B

Source address

Destination address

Data (=Payload)

net-C

5

IP Routing - What a dynamic routing protocol does -

Webサーバ

R2

R1 R3

R4

R5

R6

R7

R8

R9

133.196.16.19

202.249.10.122

From 133.196.16.19 to 202.249.10.122

A. Calculate routes (back-ground)

1. Get Routing Information in the Domain

2. Export and import routing information

(Inside/Outside Routing Domain)

202.249.xxx.yyy → R4

202.249.xxx.yyy → R6 202.249.xxx.yyy

→ R8

Import & Export

available networks

B. L3 packet transmission (on-demand)

→ Dest.＝202.249.10.122 (Best-Matching)

→ Next Hop＝“R2” for 202.249.xxx.yyy

6

L4： Application data == contents for delivery L3： IP packet == human-being L2： Data-link frame == car, train, ship, airplane L1： Physical media == road, railroad, airline

IP packet forwarding - Compare with transport system -

1. Data-link and Physical media is frequently tightly coupled.

2. We can replace data-link, whenever you want. 3. Router does not need to memorize each

human-being to visit, i.e., stateless operation

7

IP version 4 (IPv4) Header Format

0 7 8 15 16 23 24 31

TOS version header

length Total length (Bytes)

Fragment offset (13bits)

protocol-id

flag(3)

TTL header checksum

datagram-id

source IP address

destination IP address

0

1

2

3

4

options (if any)

TCP/UDP data

20 B

yte

s

IP version 6 (IPv6) Header Format

0 7 8 15 16 23 24 31

version Priority Flow Label

Hop-Limit Next Header Type Payload Length

source IP address (128 bits)

destination IP address (128 bits)

0

1

2 3 4

options (if any)

TCP/UDP data

40 B

yte

s

5 6

7

8

9

The Data, we will put on-line

1. Japanese in general

– http://v6pc.jp/jp/spread/ipv6spread2013.phtml

– IPv6 over NGN http://v6pc.jp/jp/spread/ipv6spread2013_03.phtml

2. Government institutes in Japan

– http://www.attn.jp/ipv6status/jp/go/

11

Copyright (c) 2013 Internet Initiative Japan

Inc.

13 2013/6/13

Number of source node for Queries

Source; Mr,Y.Matsuzaki of IIJ

A

AAAA

Copyright (c) 2013 Internet Initiative

Japan Inc.

14 2013/6/13

AAAA(IPv6) vs A(IPv4)

Source; Mr,Y.Matsuzaki of IIJ

50 % of

DNS Query has

already been

Dual Stack !!!

15

TLV(Type, Length and Value) format

Option Type Option Len Option Data

00- read the next header 01- drop the packet 10- drop packet to send ICMP error message 11- drop packet to send ICMP error message, if it is not multicast packet

0 – do not change option, until destination 1 – can change option, if needed

Option code point

Option Len octet

16

IP address design; good or bad ? • Two meanings by one instance

1. Identifier to identify the destination interface

2. Routing hint to forward the IP packet to the

destination interface

• Address structure for “effective” routing

– Hierarchy by recursive and aggregative configuration

• Address structure for “flexible” routing

– Provider independent address space

– Best-match policy, e.g., super-netting or punching-

hole

17

IP経路(ルーティング)制御 - 金太郎飴的(recursive)ネットワーク -

Webサーバ

202.249.10.122

メールサーバ

133.196.16.10

OSPF Backbone Network

(Area0)

AS=1210

AS=1391

AS=2913

AS=2014

AS=1998

AS=1018 IX

Area1 Area2 AreaN

Campus Net.

Campus Net. Backbone Network

POP

: Boarder Router

Dial-up access

POP

18

Aggregating routing prefixes,

to reduce the number of routing entries

• Contiguous routing prefixes can be aggregated.

Host ID 00 Network prefix

24

Host ID

01 Network prefix

Host ID

10 Network prefix

Host ID

11 Network prefix

C

C

C

C

Network prefix

22

４C

- Address Aggregation

- 4x(/24 address) → 1x(/22 adress)

Host ID

19

Aggregating Routing Prefixes

to reduce the number of routing entries

192.24.0.0 - 192.24.7.0 = 192.24.0.0/21

192.24.16.0 - 192.24.31.0 = 192.24.16.0/20

192.24.8.0 - 192.24.11.0 = 192.24.8.0/22

192.24.34.0 - 192.24.35.0 = 192.24.34.0/23

192.32.0.0 - 192.32.15.0 = 192.32.0.0/20

192.24.12.0 - 192.24.15.0 = 192.24.12.0/22

192.24.32.0 - 192.24.33.0 = 192.24.32.0/23

192.24.32.0/22 192.24.0.0/19 192.32.0.0/20

192.24.32.0/22 192.24.0.0/19 192.32.0.0/20

RA RB

20

0 1 2 3 12345678 90123456 78901234 56789012 [1] 192.32. 0.0/20 : 11000000.00100000.0000---- -------- [2] 192.24.34.0/23 : 11000000.00011000.0010001- -------- [3] 192.24.32.0/23 : 11000000.00011000.0010000- -------- [4] 192.24.16.0/20 : 11000000.00011000.0001---- -------- [5] 192.24. 0.0/21 : 11000000.00011000.00000--- -------- [6] 192.24. 8.0/22 : 11000000.00011000.000010-- -------- [7] 192.24.12.0/22 : 11000000.00011000.000011-- --------

0 1 2 3 12345678 90123456 78901234 56789012 [1] 192.32. 0.0/20 : 11000000.00100000.0000---- -------- [8] 192.24.32.0/22 : 11000000.00011000.001000-- -------- [4] 192.24.16.0/20 : 11000000.00011000.0001---- -------- [5] 192.24. 0.0/21 : 11000000.00011000.00000--- -------- [9] 192.24. 8.0/21 : 11000000.00011000.00001--- --------

Aggregate; [2] + [3] = [8] (.34/23 + .32/23) [6] + [7] = [9] (.8/22 + .12/22)

Aggregate; [5] + [9] = [10] (.0/21 + .8/21)

21

0 1 2 3 12345678 90123456 78901234 56789012 [1] 192.32. 0.0/20 : 11000000.00100000.0000---- -------- [8] 192.24.32.0/22 : 11000000.00011000.000110-- -------- [4] 192.24.16.0/20 : 11000000.00011000.0001---- -------- [10] 192.24. 0.0/20 : 11000000.00011000.0000---- --------

0 1 2 3 12345678 90123456 78901234 56789012 [1] 192.32. 0.0/20 : 11000000.00100000.0000---- -------- [8] 192.24.32.0/22 : 11000000.00011000.000110-- -------- [11] 192.24. 0.0/19 : 11000000.00011000.000----- --------

Aggregate; [5] + [9] = [10] (.0/21 + .8/21)

0 1 2 3 12345678 90123456 78901234 56789012 [1] 192.32. 0.0/20 : 11000000.00100000.0000---- -------- [8] 192.24.32.0/22 : 11000000.00011000.001000-- -------- [4] 192.24.16.0/20 : 11000000.00011000.0001---- -------- [5] 192.24. 0.0/21 : 11000000.00011000.00000--- -------- [9] 192.24. 8.0/21 : 11000000.00011000.00001--- --------

Aggregate; [4] + [10] = [11] (.16/20 + .0/20)

22

IP address design; good or bad ? • Two meanings by one instance

1. Identifier to identify the destination interface

2. Routing hint to forward the IP packet to the

destination interface

• Address structure for “effective” routing

– Hierarchy by recursive and aggregative configuration

• Address structure for “flexible” routing

– Provider independent address space

– Best-match policy, e.g., super-netting or punching-

hole

23

Super-netting Needs Best-Matching

192.24.0.0/20

192.24.0.0/23

0 1 2 3 Next-hop 12345678 90123456 78901234 56789012 192.24.0.0/20 : 11000000.00011000.0000---- -------- R1 192.24.0.0/23 : 11000000.00011000.0000000- -------- R2 : : : : : : : :

R1

R2 R3

<< Routing table in R3 >>

Destination next-hop

(1) 192.24.1.122 : R2

(2) 192.24.8.36 : R1

24

Routing

[Types of Routing] (a) Static (static_routing, default_routing) (b) Dynamic

[Jobs of Routing Process(Dynamic Routing)] (i) Advertisement of Routing information to all the neighbor nodes (ii) Calculate and establish the routing table (iii) IP packet reception and forwarding

[Procedure when receives IP packet] (1) Retrieve host_address (2) Retrieve network_address (3) Retrieve default_entry

25

Implication of routing

protocol/algorithm

• Mathematical definition

– Create an unique tree, whose root is the destination tree. There are multiple trees, in general, but, among multiple trees, the unique tree is defined by some defined cost function.

– The tree must be created for all the possible destination, including “default destination”, as a last resort.

– Creation of the complete global tree is impossible, so that recursive structure and default routing are applied to.

26

Implication of routing

protocol/algorithm

• Engineering observation

– Fully distributed path calculation, aka, no fate-share, no single-point-of-failure

– State management is independent from application data flow, aka, do not care “end-to-end”

end-to-end principle on transparency, but on path management.

27

Dynamic Routing Protocols

[calculation algorithms] (1) Distance Vector ; DV型

(2) Link State ； LS型 (3) Path Vector ； PV型 (4) Source Routing)

Routing Type DV型 LS型 PV型 Object IPv6 RIP Yes routed RIPng OSPF Yes gated OSPFv6 BGP4 Yes gated BGP4＋ DVMRP Yes mrouted － MOSPF Yes － － PIM n/a n/a n/a － － MBGP Yes － －

28

Distance Vector Routing Protocol

・ Bellman-Ford Algorithm (or Bellman-Fullkerson) - Deployed around 1969 in ARPANET - Developed by Xerox-PARC as XNS-RIP - Maintain and exchange the distance vector, indicating distance from own node to reachable destination nodes. Pick up the neighbor node, that is the shortest path to the destination node, for every possible destination nodes. - Does not have network topology information - Order of calculation and routing information is O(n), rather than O(n2) - Distance Vector ： {dst_net, distance, next_hop_node}

29

Routing Information Protocol (RIP)

・ RIP for IPv4 ; RFC 1058/1721/1722/1723/1724

RIP for IPv6 ; RFC 2080

・ routed in BSD, SunOS

- Maximum hops ; 15

- Exchange distance vector every 30sec.

- Cold-Start; max.450 sec.(=15x30sec.) for synch tables

- use the UDP(port=520)

- Keep-alive algorithm;

identify in failure without 180 sec. keep-alive message

- Calculation algorithm；

- D(i,j) ; distance vector

- d(i,j) ; distance between node_i and node_j

D(i,j) = min [d(i,k) + D(k,j)] (for all k)

30

Routing Information Protocol (RIP)

A

D

B

E

C

(3)

(1)

(6)

(4)

(2)

(5)

From A to Link Cost

A local 0

From A to Link Cost

A local 0

B (1) 1

D (3) 1

From B to Link Cost

B local 0

From D to Link Cost

D local 0

B → A

D → A

(1) 0 sec

(2) 30 sec

31

Routing Information Protocol (RIP)

A

D

B

E

C

(3)

(1)

(6)

(4)

(2)

(5)

From A to Link Cost

A local 0

B (1) 1

C (1) 2

D (3) 1

E (1) 2

B → A

D → A

(2) 30 sec

(3) 60 sec

From A to Link Cost

A local 0

B (1) 1

D (3) 1

From B to Link Cost

A (1) 1

B local 0

C (2) 1

E (4) 1

From D to Link Cost

A (3) 1

D local 0

E (6) 1

Select one from even two path

→ {(1),2} vs {(3), 2}

32

Routing Information Protocol (RIP)

A

D

B

E

C

(3)

(1)

(6)

(4)

(2)

(5)

From A to Link Cost

A local 0

B (1) 1

C (1) 2

D (3) 1

E (1) 2

B → A

D → A

(3) 60 sec

(4) 90 sec

From B to Link Cost

A (1) 1

B local 0

C (2) 1

D (1) 2

E (4) 1

From D to Link Cost

A (3) 1

B (3) 2

C (6) 2

D local 0

E (6) 1

From A to Link Cost

A local 0

B (1) 1

C (1) 2

D (3) 1

E (1) 2

33

Link State Routing Protocol

・ SFP (Shortest Path First) as OSPF and as IS-IS - Deployed around 1970 in ARPANET

→ Come up with the scaling issue of Distance Vector - Each nodes in the routing domain have the topology information and the Attribute value of all the links connecting nodes. ) - The link-state database in the nodes are synchronized and are identical. - Every node calculates the next hop nodes for every destination, using the identical routing information, with identical calculation algorithm. - The shortest path, having the minimum cost value, is defined as the appropriate path to reach to the destination nodes/networks. → calculate the best path for each destination nodes/networks, i.e., creating the Spanning_Tree

34

Open Shortest Path First (OSPF)

A

D

B

E

C

(3)

(1)

(6)

(4)

(2)

(5)

[ Link State Data-Base ]

From To Link-id Distance

A B 1 1

A D 3 1

B A 1 1

B C 2 1

B E 4 1

C B 2 1

C E 5 1

D A 3 1

D E 6 1

E B 4 1

E C 5 1

E D 6 1

Exchange

LS information

between neighbor

node

At Node “A”

To Next-Hop Link-id

B B 1

C B 1

D D 3

E B 1

A

D

B

E

C

(3)

(1)

(4)

(2)

Calculate spanning tree

Build routing

table

35

OSPF Area Configuration Example

RT1

RT2

N3

RT4

RT3

RT5

RT6

N12 N13 N14

RT10 RT17

N12

N15

N3 N9

RT9

RT12

RT11

RT8

N10

N11

N1

N2

N4

N8

N7

H1

Area 1

Area 3 Area 2

Area 0

: ASｅｓ

(3)

(3)

(1)

(1) (1)

(1)

(8) (8)

(8) (6)

(7)

(6)

(6)

(8) (8) (8)

(2)

(9)

(1) (1)

(1)

(4)

(3)

(2) (1)

(1)

(1)

(2)

(10)

(3)

(2) Ia

Ib

(7)

(6)

(5)

36

OSPF Link State DB Example

- routers in Area 1 - ** From **

RT1 RT2 RT3 RT4 RT5 RT7 N3

RT1 0

RT2 0

RT3 0

RT4 0

RT5 14 8

RT7 20 14

N1

N2

N3

N4

Ia, Ib

N6

N7

N8

N9-N11,H1

N12

N13

N14

N15

** T

O *

* 3

3 1 1 1 1

2 15 22 16 15 20 19 18 18

19 16 8 2 8 8

9

Network RT3 RT4

N1 4 4

N2 4 4

N3 1 1

N4 2 3

RT3/RT5がArea_0のRouters

(RT5/RT6)へ広告する情報

RT: Router

N : Network

I : p2p link

H : Host

Example:

RT3 → RT7 ： 20 = 8 + 8 + 6

(RT3,RT6,RT5,RT7)

37

Path Vector Routing Protocol - Defined in RFC827 (EGP; Exterior Gateway Protocol), deployed since 1982 → Designed as the routing protocol to interconnect NSFNET backbone and regional networks (RFC1093) → Designed so as to able to implement and reflect the different routing policies applied at the regional networks, i.e., policy routing. - Routing among AS (Autonomous System) AS is represented by 16 bits (now it is 32 bits). The path to reach to the destination AS is represented by the “path-vector”, that is consisted by the set of AS numbers. Each AS Boarder Router advertises all the reachable path vector information to all neighbor nodes. All the border routers in the Internet advertise and exchange AS path information, so as to create global AS Path entries for the spanning-trees covering globe.

38

PV Routing Protocol ; BGP4+

・ BGP (Border Gateway Protocol) ; RFC1771

(gated daemon in UNIX system)

(1) IBGP & EBGP

- IBGP(Internal BGP) ; Intra-AS

- EBGP(External BGP) ; Inter-AS

(2) Multiple Layer-3 Protocols by BGP4+

(3) Policy routing

(4) Full Mesh or Reflector for IBGP

(5) Route-Server operation for EBGP

→ Avoiding the Full-Mesh Peering (Start-Peering)

(6) Route Aggregation

(7) Running over TCP （port=179）

(8) Multi-Accessability

- IBGP； MED (Multiple Exit Discriminator)

- EBGP; Local Preference

39

A1,A2 B1,B2

D1 E1,E2

C1,C2

Path Vector Routing

A

D

B

E

C

(AS=5)

(AS=1) (AS=3) (AS=2)

(AS=4)

[ Path Vector Data-Base in node A]

From To Path Next-Router

A B1 A,B B

A B2 A,B B

A C1 A,B,C B

A C2 A,B,C B

A D1 A,D D

A E1 A,D,E D

A E2 A,B,E B

[ Path Vector Data-Base in node C]

From To Path Next-Router

C B1 C,B B

C B2 C,B B

C A1 C,B,A B

C A2 C,E,D,A B

C D1 A,E,D E

C E1 A,E E

C E2 A,B,E B

40

A1,A2 B1,B2

D1 E1,E2

C1,C2

Path Vector Routing

A

D

B

E

C

(AS=5)

(AS=1) (AS=3) (AS=2)

(AS=4)

(1) Step 1

From To Path Next-Router

A B1 A,B B

A B2 A,B B

A D1 A,D D

(2) Step 2

From To Path Next-Router

A B1 A,B B

A B2 A,B B

A C1 A,B,C B

A C2 A,B,C B

A D1 A,D D

A E1 A,D,E D

A E2 A,B,E B

［ From B］

From To Path Next-Router

B E1 B,E E

B E2 B,E E

B C1 B,C C

B C2 B,C C

［ From D］

From To Path Next-Router

D A1 D,A A

D A2 D,A A

D E1 D,E E

D E2 D,E E

41

B1,B2 C1,C2

Path Vector Routing ; IBGP

A

D

B

E

C

(AS=1) (AS=3)

(AS=2)

(AS=4)

Network；

A1,A2,D1

; Inter-AS （EBGP)

; Intra-AS （IBGP）

From B1 to E2 ； ｛AS=2,AS=1,AS=4｝

Path; B → （A → D） → E

From C2 to B2 ； ｛AS=3, AS=4, AS=1, AS=2｝

Path; C → （F → E） → （D → A） → B

F

Network;

E1,E2,F1

（*） IBGP； （A,D） & （E,F）

42

Avoiding Full Mesh Peering

E

D

A

C

B

E

D

A

C

B RS Full-Mesh Peering

Route

Server

E

D

A

C

B RR

Route

Reflector

“EBGP”

“IBGP”

43

NAT

(Network Address Translation)

44

IP Address for Private Use

• Reserved by IANA (RFC1918)

– This is not global unique address space.

– There are {many} nodes, that have the same IP

address.

10.0.0.0 - 10.255.255.255

172.16.0.0 - 172.31.255.255

192.168.0.0 - 192.168.255.255

45

NAT(Network Address Translation)

・ Private IP address and related port number is translated at the

NAT router, located at the edge of network segment using the

private IP addresses.

(1) Private segment → Global

- DNS; as it is (resolved global IP address of destination)

- Source IP address IP address of NAT router’s global interface

- Source Port number pick up one and register into translation table

(2) Global → Private

- DNS; NAT router’s global interface

- Destination IP address; translated into private IP address

by destination port number

[Note] Can not initiate the session from global space to private space.

We can not put a server, access from global space, in NAT segment.

46

Traditional Basic NAT

NAT A C

C A C N

A C N C

for NAT segment for global

IP Address Port IP Address Port

Src Dest Src Dest Src Dest src Dest A

-- ー ー ー ー ー Ｎ

Replace Ａ→Ｎ

Replace Ｎ→Ａ

Source address

Destination address

NAT segment Global Internet

47

Traditional NAT

NAT A C

NAT segment Global Internet

Ａ

C

Src IP

Destination IP Ｂａｓｉｃ ＮＡＴ

100

200

Src port number

Destination port Ｃ

Ｎ

100

200

200

100

Ｎ

C

Ｃ

Ａ

200

100

Replace Ａ→Ｎ

Replace Ｎ→Ａ

Ａ

C

Src IP

Destination IP

１００

２００

Src port number

Destination Port

Ｃ

Ｎ

150

200

200

150

Ｎ

C

Ｃ

Ａ

200

100

IP; Ａ→Ｎ、

Port; 100 →150

IP; Ｎ→Ａ

Port; 150→ 100

ＮＡＰＴ

48

Bi-directional NAT

NAT A C

Ａ

C

Src IP address

Dest IP address

１００

２００

Src Port number

Dest Port Number

Ｃ

Ｎ

１００

２００

２００

１００

Ｎ

C

Ｃ

Ａ

２００

１００

Replace Ａ→Ｎ

Replace Ｎ→Ａ

ＤＮＳ Query; IP for host A ?

Replay; it is N.

（３）

（４）

NAT segment Global Internet

49

192.168.3.5

NAT-R1

NAT-R2

192.20.2.24 (bill.whitehouse.gov)

192.168.0.0/16 192.20.0.0/16

192.168.32.1

198.29.10.23 198.30.40.50

192.20.61.1

dst=198.30.40.50

src=192.168.3.5

dst=198.30.40.50

src=198.30.10.23

dst=192.20.2.24

src=198.20.10.23

<Translation Table in NAT-R2>

input output output

source port destination port source port destination port port

198.29.10.23 2012 198.30.40.50 n/a 190.29.10.23 n/a 192.20.2.24 n/a #1

192.20.2.24 n/a 198.29.10.23 n/a 198.30.40.50 2122 198.29.10.23 n/a #2

#2

#1

src=198.29.10.23, port=2012

→ dst=192.20.2.24

(*) DNS Address resolution : bill.whitehouse.gov → 198.30.40.50

However…… • Limitation on the number of session states for

NAT operation

• Each user could use certain number of sessions – How many sessions ?

– Even as the best case, 65,536 is the maximum number of sessions, shared by customers accommodated into a single IPv4 address

When the number of users is 2,000, it will be only

30 sessions This means……..

50

Limitation of NAT Solution

NAT

Host

Host

Host

Host

Host

Host

Maximum # of sessions

51

Limitation of NAT Solution

NAT

Host

Host

Host

Host

Host

Host

Maximum # of sessions

You may have already

experienced !!!!

52

Max 30 Connections

53

Max 20 Connections

54

Max 15 Connections

55

Max 10 Connections

56

Max 5 Connections

57

Yet another, serious problem

1. Security…… with NAT……

2. Operational overhead (OPEX) by NAT….

58

59

Some other routing mechanisms

• Anycast

– You can advertize the same routing information

from multiple routers (or nodes).

– The IP packet is automatically delivered to the

nearest network segment (or node)

– Applied first at Nagano Olympic Game, and

applied in root DNS servers and in CDN.

• MIP(Mobile IP) / NEMO(Network Mobility)

– MIP/NEMO router acts as a rendezvous point to

mobile node/network.

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Some other routing mechanisms

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Mobile IP operational example

Home Agent

move

Mobile Node

tunnel

Mobile Node

Set the home

address as the

destination

Have both home

address and CoA

Only the routing

information for

home address is

advertised

Can select a route

either via Home

Agent or via direct

peer-to-peer path

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When we observes MIP…

• It is a separation of Locator-ID (=MPLS label, CoA address) and Host-Identifier (=MPLS FEC, home address)

It may lead to “future Internet” architecture discussion…

HIP(Host IdentityProtocol) and RISP (Routing and Identifier Separation Protocol)

Yet another approach

• NDN; Named Data Networking

– http://www.named-data.net/

– File/Content based routing

– Back ground architecture

• P2P

• DTN

• OpenFlow

– http://www.openflow.org/

– Special Lecture on June 10th

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