Linux Networks

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Linux Networks IPv6
Welcome to...

• Presentation by Carmen Buschmann
• for the MANETS project group
• University of Paderborn

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Overview
Linux Networks IPv6
Overview

• Linux Networks
• IP Addresses
• Network Interfaces
• Domain Name Server
• Routing
• Configuring Network Servers And Services

• IPv6
• IPv6 Addresses
• Header Format
• Extension Headers
• ICMP
• Upper-Layer Protocol Issues
• Converting IPv4 To IPv6

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ISO-OSI-Model TCP-Model Protocols
FTP-File Transfer Protocol HTTP-Hypertext
Transfer Protocol SMTP-Simple Mail Transfer
Protocol DNS-Domain Name Service TFTP-Trivial
File Transfer Protocol
Application
Transport
TCP-Transmission Control Protocol UDP-User
Datagram Protocol
Internet
IP-Internet Protocol
Network Access
LAN WAN Technologies
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Linux Networks IPv6
A short explanation about IPv4

• most common internet protocol
• 32-Bit format of source and destination address
• 20-Byte header for packets
• special IP-addresses Loopback 127.0.0.1,
  undefined 0.0.0.0, network address x.x.x.0,
  broadcast address x.x.x.255 (both class C)
• private networks (without routing)
• 192.168.x.x, 172.16.x.x 172.31.x.x, 10.x.x.x
• netmask (network octet set to 255, host octets
  set to 0 for A,B,C class networks)

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IP-Classes
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Linux Networks IPv6
A short explanation about IPv4
Picture of IPv4 Header
-----------------------
--------- Version IHL Type of
Service Total Length
-------------------------
------- Identification
Flags Fragment Offset
-------------------------
------- Time to Live Protocol
Header Checksum
-------------------------
-------
Source Address
-------------------------
-------
Destination Address
-------------------------
------- TCP header, then your data
......


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Network Interfaces

• Network devices created dynamically by Software
• Dont require device files to be present
• Ethernet device driver creates eth0..n
  interfaces sequentially as it locates your
  ethernet hardware during each time you boot.
• Wlan driver creates interfaces like wlan0,
  wlan1,...
• Loopback device creates lo0
• To configure a network interface
• The program most commonly used is ifconfig.
• It is found in the /dev directory
• Command root ifconfig eth0 192.168.0.1 netmask
  255.255.255.0 up
• Command ifconfig eth0 down

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Domain Name Server (DNS)

• Different collections of names have to be
  managed in large networks
• This includes the names and network addresses
  for computers
• Logging these information in each computer is
  inefficient
• Storing on central computers is more efficient
  -gt name servers
• Configuration of name resolver code
• /etc/resolv.conf
• domain subnet.upb.de
• search subnet.upb.de upb.de
• name server 131.234.22.30
• name server 131.234.137.23

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Routing in Linux
To permit machines internal to the network to be
able to send IP packets to the outside world,
enable IP Forwarding echo "1" gt
/proc/sys/net/ipv4/ip_forward  Kernel support for
advanced routing required Config_IP_Advanced_Rout
er (must be activated in Kernel
Configuration) Also to be able to forward all
packets echo 0 gt /proc/sys/net/ipv4/conf/all/rp_f
ilter
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Routing in Linux
Internet
Routingtable root route add net 192.168.1.0
netmask 255.255.255.0 eth0 root route add net
192.168.2.0 netmask 255.255.255.0 ppp0 root
route add net 192.168.3.0 netmask 255.255.255.0
ppp1 root route add default gw 192.168.3.1 dev
ppp1
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Routing in Linux
route n show numerical addresses instead of
trying to determine symbolic host names. This
is useful if you are trying to determine why
the route to your nameserver has
vanished. root_at_localhost route Kernel IP
routing table Destination Gateway
Genmask Flags Metric Ref Use
Iface 131.234.72.0
255.255.248.0 U 0 0 0
eth0 loopback 255.0.0.0
U 0 0 0 lo default
catnetz72.uni-p 0.0.0.0 UG 0 0
0 eth0 root_at_localhost route -n Kernel IP
routing table Destination Gateway
Genmask Flags Metric Ref Use
Iface 131.234.72.0 0.0.0.0
255.255.248.0 U 0 0 0
eth0 127.0.0.0 0.0.0.0 255.0.0.0
U 0 0 0 lo 0.0.0.0
131.234.72.1 0.0.0.0 UG 0 0
0 eth0
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Packet processing and forwarding
Processing takes datagram from queue from
interface - Is Target address loopback
(127.0.0.1) or own address? - Time to life lt
0? Routing receives datagram that needs to be
forwarded - consults routing table and
determines IP address and interface Fragmentation
receives datagram and forwarding information -
checks MTU (Maximum Transfer Unit) table and
compares with datagram size - MTU lt size and do
not fragment bit is set? - else divide datagram
into fragments - add header and options to each
fragment Send packets to interface for delivery
to next hop router or final destination
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Network Servers and Services

• Network servers and services are those programs
  that allow other programs (remote or local) to
  make use of your Linux machine.
• /etc/services file with standard services used
  in the network
• Each service is connected with their
  corresponding/assigned port numbers, e.g.
• ftp 21/tcp File Transfer Control
• domain 53/udp name-domain server

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Overview
Linux Networks IPv6
Overview

• IPv6
• IPv6 Addresses
• Header Format
• Extension Headers
• ICMP
• Upper-Layer Protocol Issues
• Converting IPv4 To IPv6

• Linux Networks
• IP addresses
• Network interfaces
• Domain name server
• routing
• configuring network servers and services

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IPv6 Addresses
Just when you thought you were beginning to
understand IP networking, the rules get
changed! Why?
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IPv6 Addresses
Motivation - to overcome address space
restrictions - more features - simplifications
that make IPv6 networks more managable for
example an easier header structure - security
measures And thats just a few of the advantages
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IPv6 Addresses

• - 128 bit addresses
• 8 octets of hexadecimal numbers
• possible address 18A462DEB34200000000000000
  06842C
• DEADF00D0000000000000073FEEDBEAF
• Shortcut 18A462DEB3426842C
• 1 (local host) or (unspecified
  address)
• integrated IPv4 000000000000000000000000
  194.153.11.222
• 194.153.11.222

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drumroll This is an IPv6 address
FP - format prefix (always 001) TLA - Top Level
Aggregator RES - Reserved Save (?), used for
growing TLA and NLANLA - Next Level
Aggregator SLA - Site Level Aggregator
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IPv6 Header Format
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A comparison of the IPv4 and the IPv6 Headers
-------------------------
------- Version IHL Type of Service
Total Length ---------
-----------------------
Identification Flags
Fragment Offset --------------
------------------ Time to
Live Protocol Header Checksum
----------------------
----------
Source Address
------------------------
--------
Destination Address
------------------------
--------
IPv4
IPv6
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Extension Headers

• Optional internet-layer information is encoded in
  seperate headers that may be placed between the
  IPv6 header and the upper-layer header in a
  packet.
• Hop-by-hop Options
• Routing
• Fragment
• Destination Options
• Authentication
• Encapsulating Security Payload

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Extension Headers

• Hop-By-Hop options Specifies delivery parameters
  at each hop on the way to the destination. Some
  of the fields in this type of header are used to
  alert a router to things like multicast listener
  discovery -- i.e., that this packet is part of a
  multicast and requires special processing.
• Routing header Used to supply a loose source
  route, a sort of roadmap for where packets need
  to be sent on their final destination. (IPv4 has
  a similar feature.)
• Fragment header Used similarly as in IPv4, to
  indicate that this packet is part of a fragmented
  stream, but fragmentation is only allowed on the
  part of the sender. Routers are not allowed to
  fragment payloads, which makes for better
  quality-of-service overall.

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Extension Headers

• Destination options Delivery parameters for the
  final destination
• Authentication header Used to provide data
  authentication and integrity checking
  information, but not encryption. For that, you
  need....
• Encapsulating Security and Payload header.

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ICMP
Short for Internet Control Message Protocol, an
extension to the Internet Protocol (IP) defined
by RFC 792 / RFC 2463. ICMP supports packets
containing error, control, and informational
messages. The PING command, for example, uses
ICMP to test an Internet connection.
(webopedia.com)
Short for Internet Control Message Protocol, an
extension to the Internet Protocol (IP) defined
by RFC 792 / RFC 2463. ICMP supports packets
containing error, control, and informational
messages. The PING command, for example, uses
ICMP to test an Internet connection.
(webopedia.com)
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Upper-Layer Protocol

• For use with IPv6, TCP and UDP put pseudo
  header in front of their normal headers (with
  Source and (final) destination address,
  Upper-Layer Packet Length field (header and
  data), Next Header field (value 6 for TCP or 17
  for UDP))
• UDP checksum may not be zero when packet
  orginates from IPv6 node
• ICMPv6 includes pseudo-header in checksum
  computation
• Upper-Layer Protocols that rely on Hop Limit
  or TTL ought to be upgraded to be able to
  handle obsolete packets
• When computing payload size it needs to be taken
  into account that IPv6 header is 20-Byte longer
  than IPv4 header

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Converting from IPv4 to IPv6 and back

• IPv6 has a pretty good backward compatibility
  and interoperability - can embed IPv4 addresses
• Dual capable routers and hosts - IPv6 and IPv4,
  encapsulating IPv6 packets within IPv4 headers to
  carry them over segments of the end-to-end path
  where the routers have not yet been upgraded to
  IPv6
• The header translation technique to allow the
  eventual introduction of routing topologies that
  route only IPv6 traffic, and the deployment of
  hosts that support only IPv6

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Applause!!!
So, this was my presentation. Any Questions?