Transcript Document 7515947

‫תזכורת‬
‫‪ ‬שיעור השלמה יום שישי הקרוב‬
‫‪ ‬שעות ‪9-12‬‬
‫‪ ‬מקום‪ :‬אורנשטיין ‪111‬‬
Last Week
 Basic Routing Schemes

Link State:
• broadcast link information
• Local computation on global topology

Distance vector:
• Exchange distance information with neighbors
• Local updates based on neighbors information
 Hierarchical Routing
 Broadcast and multicast
 Using a tree topology
This week
 Hierarchical routing
 IP addresses
 Definition of network
 Network Address Translation (NAT)
 Routing algorithms implementations
The Internet Network layer
Host, router network layer functions:
Transport layer: TCP, UDP
Network
layer
IP protocol
•addressing conventions
•datagram format
•packet handling conventions
Routing protocols
•path selection
•RIP, OSPF, BGP
routing
table
ICMP protocol
•error reporting
•router “signaling”
Link layer
physical layer
Lecture 6: Network Layer
#4
Hierarchical Routing
Our routing study thus far - idealization
 all routers identical
 network “flat”
… not true in practice
scale: with 50 million
destinations:
 can’t store all dest’s in
routing tables!
 routing table exchange
would swamp links!
administrative autonomy
 internet = network of
networks
 each network admin may
want to control routing in its
own network
Lecture 6: Network Layer
#5
Hierarchical Routing
 aggregate routers into
regions, “autonomous
systems” (AS)
 routers in same AS run
same routing protocol


“intra-AS” routing
protocol
routers in different AS
can run different intraAS routing protocol
gateway routers
 special routers in AS
 run intra-AS routing
protocol with all other
routers in AS
 also responsible for
routing to destinations
outside AS
 run inter-AS routing
protocol with other
gateway routers
Lecture 6: Network Layer
#6
Intra-AS and Inter-AS routing
C.b
a
C
Gateways:
B.a
A.a
b
A.c
d
A
a
b
c
a
c
B
b
•perform inter-AS
routing amongst
themselves
•perform intra-AS
routers with other
routers in their
AS
network layer
inter-AS, intra-AS
routing in
gateway A.c
link layer
physical layer
Lecture 6: Network Layer
#7
Intra-AS and Inter-AS routing
C.b
a
Host
h1
C
b
A.a
Inter-AS
routing
between
A and B
A.c
a
d
c
b
A
Intra-AS routing
within AS A
B.a
a
c
B
Host
h2
b
Intra-AS routing
within AS B
 We’ll examine specific inter-AS and intra-AS
Internet routing protocols shortly
Lecture 6: Network Layer
#8
AS D
Routing: Example
E
d
AS A
(OSPF)
a2
F
No Export
to F
a1
i
AS C
AS B
i2
(OSPF intra
routing)
b
AS I
Lecture 6: Network Layer
#9
AS D
Routing: Example
E
d1
d
d2
AS A
(OSPF)
a2
F
i
AS C
a1
How to specify?
AS B
(OSPF intra
routing)
b
AS I
Lecture 6: Network Layer
#10
IP Addressing Scheme
 We need an address to uniquely identify
each destination
 Routing scalability needs flexibility in
aggregation of destination addresses
 we
should be able to aggregate a set of
destinations as a single routing unit
 Preview: the unit of routing in the Internet
is a network---the destinations in the routing
protocols are networks
Lecture 6: Network Layer
#11
IP Addressing: introduction
 IP address: 32-bit
identifier for host,
router interface
 interface: connection
between host, router
and physical link



router’s typically have
multiple interfaces
host may have multiple
interfaces
IP addresses
associated with
interface, not host, or
router
223.1.1.1
223.1.2.1
223.1.1.2
223.1.1.4
223.1.1.3
223.1.2.9
223.1.3.27
223.1.2.2
223.1.3.2
223.1.3.1
223.1.1.1 = 11011111 00000001 00000001 00000001
223
1
1
Lecture 6: Network Layer
1
#12
IP Addressing
 IP address:
 network part
• high order bits

host part
• low order bits
 What’s a network ?
(from IP address
perspective)
 device interfaces with
same network part of
IP address
 can physically reach
each other without
intervening router
223.1.1.1
223.1.2.1
223.1.1.2
223.1.1.4
223.1.1.3
223.1.2.9
223.1.3.27
223.1.2.2
LAN
223.1.3.1
223.1.3.2
network consisting of 3 IP networks
(for IP addresses starting with 223,
first 24 bits are network address)
Lecture 6: Network Layer
#13
IP Addressing
How to find the
networks?
 Detach each
interface from
router, host
 create “islands of
isolated networks
223.1.1.2
223.1.1.1
223.1.1.4
223.1.1.3
223.1.9.2
223.1.7.0
223.1.9.1
223.1.7.1
223.1.8.1
223.1.8.0
223.1.2.6
Interconnected
system consisting
of six networks
223.1.2.1
223.1.3.27
223.1.2.2
223.1.3.1
223.1.3.2
Lecture 6: Network Layer
#14
IP Addresses
given notion of “network”, let’s re-examine IP addresses:
“class-full” addressing:
class
A
0 network
B
10
C
110
D
1110
1.0.0.0 to
127.255.255.255
host
network
128.0.0.0 to
191.255.255.255
host
network
multicast address
host
192.0.0.0 to
223.255.255.255
224.0.0.0 to
239.255.255.255
32 bits
Lecture 6: Network Layer
#15
IP addressing: CIDR
 classful addressing:


inefficient use of address space, address space exhaustion
e.g., class B net allocated enough addresses for 65K hosts,
even if only 2K hosts in that network
 CIDR: Classless InterDomain Routing


network portion of address of arbitrary length
address format: a.b.c.d/x, where x is # bits in network
portion of address
network
part
host
part
11001000 00010111 00010000 00000000
200.23.16.0/23
Lecture 6: Network Layer
#16
CIDR Address Aggregation
AS D
d
d1
AS A
(OSPF)
130.132.1/24
i
i->a1: I can reach
130.132/16; my
path: I
a2
a1
130.132.2/24
AS I
intradomain
routing uses /24
130.132.3/24
Lecture 6: Network Layer
#17
CIDR Address Aggregation
B
x00/24: B
A
x01/24: C
C
x10/24: E
G
E
x11/24: F
F
Lecture 6: Network Layer
#18
IP addresses: how to get one?
Hosts (host portion):
 hard-coded by system admin in a file
 DHCP: Dynamic Host Configuration Protocol:
dynamically get address: “plug-and-play”
 host broadcasts “DHCP discover” msg
 DHCP server responds with “DHCP offer” msg
 host requests IP address: “DHCP request” msg
 DHCP server sends address: “DHCP ack” msg
 The common practice in LAN and home access
(why?)
Lecture 6: Network Layer
#19
IP addresses: how to get one?
Network (network portion):
 get allocated portion of ISP’s address space:
ISP's block
11001000 00010111 00010000 00000000
200.23.16.0/20
Organization 0
11001000 00010111 00010000 00000000
200.23.16.0/23
Organization 1
11001000 00010111 00010010 00000000
200.23.18.0/23
Organization 2
...
11001000 00010111 00010100 00000000
…..
….
200.23.20.0/23
….
Organization 7
11001000 00010111 00011110 00000000
200.23.30.0/23
Lecture 6: Network Layer
#20
Hierarchical addressing: route aggregation
Hierarchical addressing allows efficient advertisement of routing
information:
Organization 0
200.23.16.0/23
Organization 1
200.23.18.0/23
Organization 2
200.23.20.0/23
Organization 7
.
.
.
.
.
.
Fly-By-Night-ISP
“Send me anything
with addresses
beginning
200.23.16.0/20”
Internet
200.23.30.0/23
ISPs-R-Us
“Send me anything
with addresses
beginning
199.31.0.0/16”
Lecture 6: Network Layer
#21
Hierarchical addressing: more specific
routes
ISPs-R-Us has a more specific route to Organization 1
Organization 0
200.23.16.0/23
Organization 2
200.23.20.0/23
Organization 7
.
.
.
.
.
.
Fly-By-Night-ISP
“Send me anything
with addresses
beginning
200.23.16.0/20”
Internet
200.23.30.0/23
ISPs-R-Us
Organization 1
200.23.18.0/23
“Send me anything
with addresses
beginning 199.31.0.0/16
or 200.23.18.0/23”
Lecture 6: Network Layer
#22
Network Address Translation: Motivation
 A local network uses just one public IP address as far as outside
world is concerned
 Each device on the local network is assigned a private IP address
rest of
Internet
local network
(e.g., home network)
192.168.1.0/24
192.168.1.2
192.168.1.1
192.168.1.3
138.76.29.7
192.168.1.4
All datagrams leaving local
network have same single source
NAT IP address: 138.76.29.7,
different source port numbers
Datagrams with source or
destination in this network
have 192.168.1/24 address for
source, destination (as usual)
Lecture 6: Network Layer
#23
NAT: Network Address Translation
Implementation: NAT router must:



outgoing datagrams: replace (source IP address, port
#) of every outgoing datagram to (NAT IP address,
new port #)
. . . remote clients/servers will respond using (NAT
IP address, new port #) as destination addr.
remember (in NAT translation table) every (source
IP address, port #) to (NAT IP address, new port #)
translation pair
incoming datagrams: replace (NAT IP address, new
port #) in dest fields of every incoming datagram
with corresponding (source IP address, port #)
stored in NAT table
Lecture 6: Network Layer
#24
NAT: Network Address Translation
NAT translation table
WAN side addr
LAN side addr
1: host 192.168.1.2
2: NAT router
sends datagram to
changes datagram
138.76.29.7, 5001 192.168.1.2, 3345
128.119.40.186, 80
source addr from
……
……
192.168.1.2, 3345 to
138.76.29.7, 5001,
S: 192.168.1.2, 3345
updates table
D: 128.119.40.186, 80
2
S: 138.76.29.7, 5001
D: 128.119.40.186, 80
138.76.29.7
S: 128.119.40.186, 80
D: 138.76.29.7, 5001
3: Reply arrives
dest. address:
138.76.29.7, 5001
3
192.168.1.2
1
192.168.1.1
192.168.1.3
S: 128.119.40.186, 80
D: 192.168.1.2, 3345
4
192.168.1.4
4: NAT router
changes datagram
dest addr from
138.76.29.7, 5001 to 192.168.1.2, 3345
Lecture 6: Network Layer
#25
Network Address Translation: Advantages
 No need to be allocated range of addresses
from ISP: - just one public IP address is
used for all devices
16-bit port-number field allows 60,000
simultaneous connections with a single LAN-side
address !
 can change ISP without changing addresses of
devices in local network
 can change addresses of devices in local network
without notifying outside world

 Devices inside local net not explicitly
addressable, visible by outside world (a
security plus)
Lecture 6: Network Layer
#26
NAT: Network Address Translation
 If both hosts are behind different NAT,
they will have difficulty establishing
connection
 NAT is controversial:
 routers should process up to only layer 3
 violates end-to-end argument
• NAT possibility must be taken into account by app
designers, e.g., P2P applications

address shortage should instead be solved by
having more addresses --- IPv6 !
Lecture 6: Network Layer
#27
IP addressing: the last word...
Q: How does an ISP get block of addresses?
A: ICANN: Internet Corporation for Assigned
Names and Numbers
 allocates addresses
 manages DNS
 assigns domain names, resolves disputes
Lecture 6: Network Layer
#28
Getting a datagram from source to dest.
routing table in A
Dest. Net. next router Nhops
223.1.1
223.1.2
223.1.3
IP datagram:
misc source dest
fields IP addr IP addr
data
A
 datagram remains
unchanged, as it travels
source to destination
 addr fields of interest
here
 mainly dest. IP addr
223.1.1.4
223.1.1.4
1
2
2
223.1.1.1
223.1.2.1
B
223.1.1.2
223.1.1.4
223.1.2.9
223.1.3.27
223.1.1.3
223.1.3.1
223.1.2.2
E
223.1.3.2
Lecture 6: Network Layer
#29
Getting a datagram from source to dest.
misc
data
fields 223.1.1.1 223.1.1.3
Dest. Net. next router Nhops
223.1.1
223.1.2
223.1.3
Starting at A, given IP
datagram addressed to B:
 look up net. address of B
 find B is on same net. as A
A
223.1.1.1
223.1.2.1
 link layer will send datagram
directly to B inside link-layer
frame
 B and A are directly
connected
223.1.1.4
223.1.1.4
1
2
2
B
223.1.1.2
223.1.1.4
223.1.2.9
223.1.3.27
223.1.1.3
223.1.3.1
223.1.2.2
E
223.1.3.2
Lecture 6: Network Layer
#30
Getting a datagram from source to dest.
misc
data
fields 223.1.1.1 223.1.2.2
Dest. Net. next router Nhops
223.1.1
223.1.2
223.1.3
Starting at A, dest. E:
 look up network address of E
 E on different network
A, E not directly attached
routing table: next hop
router to E is 223.1.1.4
link layer sends datagram to
router 223.1.1.4 inside linklayer frame
datagram arrives at 223.1.1.4
continued…..
A
223.1.1.4
223.1.1.4
1
2
2
223.1.1.1





223.1.2.1
B
223.1.1.2
223.1.1.4
223.1.2.9
223.1.3.27
223.1.1.3
223.1.3.1
223.1.2.2
E
223.1.3.2
Lecture 6: Network Layer
#31
Getting a datagram from source to dest.
misc
data
fields 223.1.1.1 223.1.2.2
Arriving at 223.1.4,
destined for 223.1.2.2
 look up network address of E
 E on same network as router’s
interface 223.1.2.9
 router, E directly attached
 link layer sends datagram to
223.1.2.2 inside link-layer
frame via interface 223.1.2.9
 datagram arrives at
223.1.2.2!!! (hooray!)
Dest.
next
network router Nhops interface
223.1.1
223.1.2
223.1.3
A
-
1
1
1
223.1.1.4
223.1.2.9
223.1.3.27
223.1.1.1
223.1.2.1
B
223.1.1.2
223.1.1.4
223.1.2.9
223.1.3.27
223.1.1.3
223.1.3.1
223.1.2.2
E
223.1.3.2
Lecture 6: Network Layer
#32
IP datagram format
IP protocol version
number
header length
(bytes)
“type” of data
max number
remaining hops
(decremented at
each router)
upper layer protocol
to deliver payload to
32 bits
head. type of
length
len service
fragment
16-bit identifier flgs
offset
time to upper
Internet
layer
live
checksum
ver
total datagram
length (bytes)
for
fragmentation/
reassembly
32 bit source IP address
32 bit destination IP address
Options (if any)
data
(variable length,
typically a TCP
or UDP segment)
E.g. timestamp,
record route
taken, specify
list of routers
to visit.
Lecture 6: Network Layer
#33
IP Fragmentation & Reassembly
 network links have MTU
(max.transfer size) - largest
possible link-level frame.
 different link types,
different MTUs
 large IP datagram divided
(“fragmented”) within net
 one datagram becomes
several datagrams
 “reassembled” only at final
destination
 IP header bits used to
identify, order related
fragments
fragmentation:
in: one large datagram
out: 3 smaller datagrams
reassembly
Network Layer
4-34
IP Fragmentation and Reassembly
Example
 4000 byte
datagram
 MTU = 1500 bytes
1480 bytes in
data field
offset =
1480/8
length ID fragflag offset
=4000 =x
=0
=0
One large datagram becomes
several smaller datagrams
length ID fragflag offset
=1500 =x
=1
=0
length ID fragflag offset
=1500 =x
=1
=185
length ID fragflag offset
=1060 =x
=0
=370
Network Layer
4-35
Routing in the Internet
 The Global Internet consists of Autonomous Systems
(AS) interconnected with each other:



Stub AS: small corporation
Multihomed AS: large corporation (no transit)
Transit AS: provider
 Two-level routing:
 Intra-AS: administrator is responsible for choice
 Inter-AS: unique standard
Lecture 6: Network Layer
#36
Internet AS Hierarchy
Inter-AS border (exterior gateway) routers
Intra-AS interior (gateway) routers
Lecture 6: Network Layer
#37
Intra-AS Routing
 Also known as Interior Gateway Protocols (IGP)
 Most common IGPs:

RIP: Routing Information Protocol

OSPF: Open Shortest Path First

IGRP: Interior Gateway Routing Protocol (Cisco
propr.)
Lecture 6: Network Layer
#38
RIP ( Routing Information Protocol)
 Distance vector algorithm
 Included in BSD-UNIX Distribution in 1982
 Distance metric: # of hops (max = 15 hops)
 why?
 Distance vectors: exchanged every 30 sec via
Response Message (also called advertisement)
 Each advertisement: route to up to 25 destination
nets
Lecture 6: Network Layer
#39
RIP (Routing Information Protocol)
z
w
A
x
D
y
B
C
Destination Network
w
y
z
x
….
Next Router
Num. of hops to dest.
….
....
A
B
B
--
2
2
7
1
Routing table in D
Lecture 6: Network Layer
#40
RIP: Link Failure and Recovery
If no advertisement heard after 180 sec -->
neighbor/link declared dead
 routes via neighbor invalidated
 new advertisements sent to neighbors
 neighbors in turn send out new advertisements (if
tables changed)
 link failure info quickly propagates to entire net
 poison reverse used to prevent ping-pong loops
(infinite distance = 16 hops)
Lecture 6: Network Layer
#41
OSPF (Open Shortest Path First)
 “open”: publicly available
 Uses Link State algorithm
 LS packet dissemination
 Topology map at each node
 Route computation using Dijkstra’s algorithm
 OSPF advertisement carries one entry per neighbor
router
 Advertisements disseminated to entire AS (via
flooding)
Lecture 6: Network Layer
#42
OSPF “advanced” features (not in RIP)
 Security: all OSPF messages authenticated (to
prevent malicious intrusion); TCP connections used
 Multiple same-cost paths allowed

only one path in RIP
 For each link, multiple cost metrics for different
ToS (eg, satellite link cost set “low” for best effort;
high for real time)
 Integrated uni- and multicast support:

Multicast OSPF (MOSPF) uses same topology data base as
OSPF
 Hierarchical OSPF in large domains.
Lecture 6: Network Layer
#43
Hierarchical OSPF
Lecture 6: Network Layer
#44
Hierarchical OSPF
 Two-level hierarchy: local area, backbone.
Link-state advertisements only in area
 each nodes has detailed area topology; only know
direction (shortest path) to nets in other areas.
 Area border routers: “summarize” distances to nets
in own area, advertise to other Area Border routers.
 Backbone routers: run OSPF routing limited to
backbone.
 Boundary routers: connect to other ASs.

Lecture 6: Network Layer
#45
IGRP (Interior Gateway Routing Protocol)
 CISCO proprietary; successor of RIP (mid 80s)
 Distance Vector, like RIP
 several cost metrics (delay, bandwidth, reliability,
load etc)
 uses TCP to exchange routing updates
 Loop-free routing via Distributed Updating Alg.
(DUAL) based on diffused computation
Lecture 6: Network Layer
#46
Inter-AS routing
Lecture 6: Network Layer
#47
Internet inter-AS routing: BGP
 BGP (Border Gateway Protocol): the de facto
standard
 Path Vector protocol:
 similar to Distance Vector protocol
 each Border Gateway broadcast to neighbors
(peers) entire path (I.e, sequence of ASs) to
destination
 E.g., Gateway X may send its path to dest. Z:
Path (X,Z) = X,Y1,Y2,Y3,…,Z
Lecture 6: Network Layer
#48
Internet inter-AS routing: BGP
Suppose: gateway X send its path to peer gateway W
 W may or may not select path offered by X
 cost, policy (don’t route via competitors AS), loop
prevention reasons.
 If W selects path advertised by X, then:
Path (W,Z) = W, Path (X,Z)
 Note: X can control incoming traffic by controlling its
route advertisements to peers:
 e.g., don’t want to route traffic to Z -> don’t
advertise any routes to Z
Lecture 6: Network Layer
#49
Internet inter-AS routing: BGP
 BGP messages exchanged using TCP.
 BGP messages:
OPEN: opens TCP connection to peer and
authenticates sender
 UPDATE: advertises new path (or withdraws old)
 KEEPALIVE keeps connection alive in absence of
UPDATES; also ACKs OPEN request
 NOTIFICATION: reports errors in previous msg;
also used to close connection

Lecture 6: Network Layer
#50
Why different Intra- and Inter-AS routing ?
Policy:
 Inter-AS: admin wants control over how its traffic
routed, who routes through its net.
 Intra-AS: single admin, so no policy decisions needed
Scale:
 hierarchical routing saves table size, reduced update
traffic
Performance:
 Intra-AS: can focus on performance
 Inter-AS: policy may dominate over performance
Lecture 6: Network Layer
#51
Extra
Lecture 6: Network Layer
#52
ICMP: Internet Control Message Protocol
 used by hosts & routers to
communicate network-level
information
 error reporting:
unreachable host, network,
port, protocol
 echo request/reply (used
by ping)
 network-layer “above” IP:
 ICMP msgs carried in IP
datagrams
 ICMP message: type, code plus
first 8 bytes of IP datagram
causing error
Type
0
3
3
3
3
3
3
4
Code
0
0
1
2
3
6
7
0
8
9
10
11
12
0
0
0
0
0
description
echo reply (ping)
dest. network unreachable
dest host unreachable
dest protocol unreachable
dest port unreachable
dest network unknown
dest host unknown
source quench (congestion
control - not used)
echo request (ping)
route advertisement
router discovery
TTL expired
bad IP header
Network Layer
4-53
Traceroute and ICMP
 Source sends series of
UDP segments to dest



First has TTL =1
Second has TTL=2, etc.
Unlikely port number
 When nth datagram arrives
to nth router:



Router discards datagram
And sends to source an
ICMP message (type 11,
code 0)
Message includes name of
router& IP address
 When ICMP message
arrives, source calculates
RTT
 Traceroute does this 3
times
Stopping criterion
 UDP segment eventually
arrives at destination host
 Destination returns ICMP
“dest port unreachable”
packet (type 3, code 3)
 When source gets this
ICMP, stops.
Network Layer
4-54
Example: tracert www.yahoo.com
Tracing route to www-real.wa1.b.yahoo.com [69.147.76.15]
over a maximum of 30 hops:
1
2
3
4
5
6
7
8
9
10
11
<1 ms
<1 ms
<1 ms
1 ms
1 ms
87 ms
87 ms
177 ms
180 ms
177 ms
177 ms
<1 ms <1 ms 132.67.250.1
1 ms <1 ms dmz-cc-gw.math.tau.ac.il [132.67.252.2]
<1 ms <1 ms tel-aviv.tau.ac.il [132.66.4.1]
<1 ms <1 ms gp1-tau-ge.ilan.net.il [128.139.191.70]
*
1 ms gp0-gp1-te.ilan.net.il [128.139.188.2]
86 ms 87 ms iucc.rt1.fra.de.geant2.net [62.40.125.121]
87 ms 87 ms TenGigabitEthernet7-3.ar1.FRA4.gblx.net [207.138.144.45]
177 ms 177 ms 204.245.39.226
177 ms 265 ms ae1-p151.msr2.re1.yahoo.com [216.115.108.23]
177 ms 177 ms te-9-4.bas-a2.re1.yahoo.com [66.196.112.203]
177 ms 177 ms f1.www.vip.re1.yahoo.com [69.147.76.15]
Trace complete.
IPv6
 Initial motivation: 32-bit address space soon
to be completely allocated.
 Additional motivation:
header format helps speed processing/forwarding
 header changes to facilitate QoS
IPv6 datagram format:
 fixed-length 40 byte header
 no fragmentation allowed

Network Layer
4-56
IPv6 Header (Cont)
Priority: identify priority among datagrams in flow
Flow Label: identify datagrams in same “flow.”
(concept of“flow” not well defined).
Next header: identify upper layer protocol for data
Network Layer
4-57
Other Changes from IPv4
 Checksum: removed entirely to reduce
processing time at each hop
 Options: allowed, but outside of header,
indicated by “Next Header” field
 ICMPv6: new version of ICMP
additional message types, e.g. “Packet Too Big”
 multicast group management functions

Network Layer
4-58
Transition From IPv4 To IPv6
 Not all routers can be upgraded simultaneous
no “flag days”
 How will the network operate with mixed IPv4 and
IPv6 routers?

 Tunneling: IPv6 carried as payload in IPv4
datagram among IPv4 routers
Network Layer
4-59
Tunneling
Logical view:
Physical view:
A
B
IPv6
IPv6
A
B
C
IPv6
IPv6
IPv4
Flow: X
Src: A
Dest: F
data
A-to-B:
IPv6
E
F
IPv6
IPv6
D
E
F
IPv4
IPv6
IPv6
tunnel
Src:B
Dest: E
Src:B
Dest: E
Flow: X
Src: A
Dest: F
Flow: X
Src: A
Dest: F
data
data
B-to-C:
IPv6 inside
IPv4
B-to-C:
IPv6 inside
IPv4
Flow: X
Src: A
Dest: F
data
E-to-F:
IPv6
Network Layer
4-60
IPv6 status report
 Operating systems –
 wide
support – early 2000
 Windows (2000, XP, Vista), BSD, Linux, Apple
 Networking infrastructure
 Cisco
 Deployment
 Slow
 Penetration
Host - minor (less than 1%)
 Used in 2008 in China Olympic games

 Motivation: CIDR & NAT
Lecture 7: Network Layer II
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