Networking 1

Mobile Communications

Fundamental Networking

Manuel P. Ricardo

Faculdade de Engenharia da Universidade do Porto

Networking 2

♦ What networking concepts shall I have present from previous courses?

♦ What are the differences between L2 and L3 networks?

♦ What is a tunnel? What is a virtual network? Why are they relevant?♦ What is a tunnel? What is a virtual network? Why are they relevant?

♦ What are the differences between IPv6 and IPv4?

Networking 3

Switching: Circuits, Virtual Circuits, Datagram

Networking 4

Circuit Switching

♦ Technologies: ISDN: Basic Rate Access, E1 Ł time slots for 64 kbit/s channels

♦ Path defined during call establishment, based on the called number

♦ Switching

» Exchange of time slots

» In time and in space

» Inputs required to be synchronised

Networking 5

Virtual Circuit Switching

♦ Technologies: ATM, MPLS

♦ Path

» defined during the virtual circuit establishment

» Defined as a set of nodes, ports, labels

♦ Switching

» Cells, packets

» Exchange of labels» Exchange of labels

Tabela de translação de

portas / canais virtuais

1

M

a

t

1

N

2

t

Entrada

M

abc

yzc

1N2

21N

kh

m

nng

Saída

1

Porta CV Porta CV

comutação

espacial

comutação

de etiqueta

b c c

y c z y

controlo de

comutação

g h

n

k kn

m

g

cabeçalho

dados

a, b, c, ... indicador de canal virtual

b a

Networking 6

Packet Switching

♦ Technologies: Ethernet, IP

♦ Path defined by packet destination address

Networking 7

To Think About

♦ Suppose terminal a moves from port 2 to port 1

» What needs to be done so that terminal a can continue receiving packets?

Networking 8

L2 Networking – Frame Formats

Ethernet

7x 10101010 10101011

Protocolo=IP

PPPBit stuffing – 5 1s seguidos ŁŁŁŁ emissor introduz 0

Networking 9

L2 Networking - Bridges

♦ Bridge builds forwarding tables automatically

♦ Address learning

» Source Address of received frame is associated to a bridge input portŁ station reachable through that port

♦ Frame forwarding♦ Frame forwarding

» When a frame is received, its Destination Address is analysed– If address is associated to a port à frame forwarded to that port

– If not à frame transmitted through all the ports but the input port

Networking 10

L2 Networking - Single Tree Required

• Ethernet frame

– No hop-count

– Could loop forever in a L2 mis-configured network

– Same for broadcast packet

• Layer 2 network

– Required to have tree topology

– Single path between

every pair of stations

• Spanning Tree (ST) Protocol

– Running in bridges

– Helps building the spanning tree

– Blocks ports

Networking 11

Ethernet Switch

The computer attached to a port gets the illusion to have

» its own LAN segment

» its LAN segment bridged to all the other segments

Networking 12

Virtual LANs

♦ One bridge simulates multiple LANs / broadcast domains

♦ One LAN may be extended to other bridges

w xw

y

VLAN 100

VLAN 200

B1

x

z

VLAN 100

VLAN 200

B2

[da=w; sa=x; data]

[da=w; sa=x; vlanid=100; data]

[da=w; sa=x; data]

Networking 13

L3 Networking – Packet Formats

Version HLen TOS Length

Ident Flags Offset

TTL Protocol Checksum

SourceAddr

0 4 8 16 19 31

Version Traffic Class Flow Label

Payload Lengtht Next Header Hop Limit

SourceAddr (4 words)

0 4 8 16 24 31

SourceAddr

DestinationAddr

Options (variable)Pad

(variable)

Data

DestinationAddr (4 words)

Options (variable number)

Data

IPv4 IPv6

Networking 14

L3 Networking – Router

3ª generation router

Networking 15

L3 Networking – Multiple Trees …

♦ Every router

» finds the shortest path to the other routers and their attached networks

» Calculates its Shortest Path Tree (SPT)

♦ Routing protocol

» Run in routers» Run in routers

» Helps routers build their SPT

» RIP, OSPF, BGP

Destination Cost NextHop

A 1 A

C 1 C

D 2 C

E 2 A

F 2 A

G 3 A

B’s routing view

D

G

A

F

E

B

C

Networking 16

TCP

♦ Point to connection between a client and a server; port-to-port

♦ Reliable, flow control Sender

Data (SequenceNum)

Acknowledgment +AdvertisedWindow

Receiver

♦ Congestion control

AdvertisedWindow

Networking 17

Multimedia Traffic - Taxonomy

Applications

Elastic Real time (variation of the packet end-to-end delay)

Intolerant Tolerant

Nonadaptive Adaptive

Delay adaptiveRate adaptive

(packet loss)

(application reaction to packet loss)

(type of reaction)

Networking 18

RTP+RTCP/UDP

♦ Multimedia traffic

♦ Application-Level Framing

♦ Data Packets (RTP)

» sequence number

» timestamp (app defines “tick”)» timestamp (app defines “tick”)

» transported as UDP packets

♦ Control Packets (RTCP)

» sent periodically

» report loss rate (fraction of packets received since last report)

» report measured jitter

Networking 19

Traditional TCP/IP Communications Stack

IETF IP address

based

switching

T1

IP

TCP

APP

T1 | T2 T2 | T3

IP

T3 | T4

IP

T5

IP

TCP

APP

host bridge router router host

T4 | T5

bridge

IEEE MAC address

based

switching

Networking 20

Tunnel IP-in-IP

T1

IP

TCP

APP

T1 | T2 T2 | T3

IP

T3 | T4 T5

IP

TCP

APP

H1 bridge R1 R2 Server

T4 | T5

bridge

IP IP

IP

outer IP header inner IP header data

DA= 2nd IP address of R2SA= 2nd IP address of H1

TTLIP identification

IP-in-IP IP checksumflags fragment offset

lengthTOSver. IHL

DA= ServerSA=H1

TTLIP identification

lay. 4 prot. IP checksumflags fragment offset

lengthTOSver. IHL

TCP/UDP/ ... payload

Networking 21

Tunnel PPP over IP (E.g PPTP)

T1

IP

TCP

APP

T1 | T2 T2 | T3

IP

T3 | T4 T5

IP

TCP

APP

H1 bridge R1 R2 Server

T4 | T5

bridge

IP IP

IP

PPP

GREGRE

PPP

» GRE

– virtual point-to-point link

– routers at remote points

– over an IP network

» PPP adequate for

– Authentication

– Transporting IP packets

Networking 22

PPP over Ethernet

Networking 23

IPv6IPv6

Networking 24

A New IP Required

♦ IPv4– Small addressing space (32 bits)

– Non-continuous usage

– Some solutions used to overcome these problems

private networks (NAT), classless networks (CDIR)

♦ IETF developed new IP version: IPv6– Same principles of IPv4

– Many improvements

– Header re-defined

♦ IPv6 may be relevant for mobile communications

Networking 25

IPv6 – Improvements

» 128 bit addresses (16 octets, 8 shorts ). No classes

» Better QoS support (flow label)

» Native security functions (peer authentication, data encryption)

» Autoconfiguration (Plug-n-play)

» Routing

» Multicast

Networking 26

♦ 8 x 16 bit, hexadecimal. Separated by :

47CD : 1234 : 3200 : 0000 : 0000 : 4325 : B792 : 0428

♦ Compressed format: FF01:0:0:0:0:0:0:43 àààà FF01::43

Address Representation

♦ Compatibility with IPv4: 0:0:0:0:0:0:13.1.68.3 or ::13.1.68.3

♦ Loopback address: ::1

♦ Network prefix described by / , same as IPv4

» FEDC:BA98:7600::/40 àààà network prefix = 40 bits

Networking 27

Reserved Addresses

Allocation Prefix Fraction of(binary) Address Space

----------------------------------- -------- -------- -----Unassigned 0000 0000 1/256Unassigned 0000 0001 1/256Reserved for NSAP Allocation 0000 001 1/128Unassigned 0000 01 1/64Unassigned 0000 1 1/32Unassigned 0001 1/16Unassigned 0001 1/16Global Unicast 001 1/8 Unassigned 010 1/8Unassigned 011 1/8Unassigned 100 1/8Unassigned 101 1/8Unassigned 110 1/8Unassigned 1110 1/16Unassigned 1111 0 1/32Unassigned 1111 10 1/64Unassigned 1111 110 1/128Unassigned 1111 1110 0 1/512Link-Local Unicast Addresses 1111 1110 10 1/1024Site-Local Unicast Addresses 1111 1110 11 1/1024Multicast Addresses 1111 1111 1/256

Networking 28

Addresses –

Link-Local, Site-Local, Global Unicast, Anycast

» Link-Local

– Used for communication between hosts in the same LAN /link

– Address built from MAC address

– Routers do not foward packets having Link-Local destination addresses

» Site-Local

– Not used anymore– Not used anymore

» Global Unicast

– Global addresses

– Address: network prefix + computer identifier

– Structured prefixes

Network aggregation; less entries in the forwarding tables

» Anycast

– Group address; packet is received by any (only one) member of the group

» Multicast

– Group address; packet received by all the members of the group

Networking 29

Address Format

| n bits | m bits | 128-n- m bits | Global Unicast Address+------------------------+-----------+------------- ---------------+ (2000::/3)|001 global rout prefix | subnet ID | interf ace ID |+------------------------+-----------+------------- ---------------+

| 10 |

| bits | 54 bits | 64 bits | Link-Local Unicast address+----------+-------------------------+------------- ---------------+ (fe80::/10)|1111111010| 0 | interf ace ID | +----------+-------------------------+------------- ---------------+

| 10 |

| bits | 54 bits | 64 b its | Site-Local Unicast address+----------+-------------------------+------------- ---------------+ (fec0::/10) |1111111011| subnet ID | interf ace ID |+----------+-------------------------+------------- ---------------+

| n bits | 128-n bits | Anycast address+------------------------------------------------+- ---------------+| subnet prefix | 00000000000000 |+------------------------------------------------+- ---------------+

| 8 | 4 | 4 | 112 bits |+------ -+----+----+-------------------------------- -------------+|11111111|flgs|scop| group ID |+--------+----+----+------------------------------- --------------+

Multicast addressScope – link, site, global, ...

(ff::/8)

Networking 30

Headers IPv4 and IPv6

Version HLen TOS Length

Ident Flags Offset

TTL Protocol Checksum

SourceAddr

0 4 8 16 19 31

Version Traffic Class Flow Label

Payload Lengtht Next Header Hop Limit

SourceAddr (4 words)

0 4 8 16 24 31

SourceAddr

DestinationAddr

Options (variable)Pad

(variable)

Data

DestinationAddr (4 words)

Options (variable number)

Data

IPv4 IPv6

Networking 31

IPv6 Header

♦ Flow label à identifies packet flow

» QoS, resource reservation

» Packets receive same service

♦ Payload length

Version Traffic Class Flow Label

Payload Lengtht Next Header Hop Limit

SourceAddr (4 words)

0 4 8 16 24 31

♦ Payload length

» Header not included

♦ Hop limit = TTL (v4)

♦ Next header

» Identifies next header/extension

♦ Options à included as extension headers

DestinationAddr (4 words)

Options (variable number)

Data

Networking 32

Extension Headers

IPv6 HeaderNext Header = TCP

TCP header + data

Routing HeaderNext Header = TCP

TCP header + dataIPv6 HeaderNext Header = Routing

IPv6 HeaderNext Header = Routing

Routing HeaderNext Header = Fragment

Fragment HeaderNext Header = TCP

Fragment of

TCP header + data

IPv6 Hop-by-hop TCPDestination Routing Fragment Authenticate. ESP

Networking 33

Extension Headers

» Hop-by-hop

additional information, inspected by every node traversed by the packet

Other header are inspected only at the destination or at pre-defined nodes

» Destination: Information for the destination node» Destination: Information for the destination node

» Routing: List of nodes to be visited by the packet

» Fragmentation: Made by the source; it shall find MPU

» Authentication: Authentication (signature) of packet header

» ESP: Data encryption

Networking 34

Routing Header -

Pacote sent from S to D, through I1, I2, I3As the packet travels from S to I1:

Source Address = S Hdr Ext Len = 6Destination Address = I1 Segments Left = 3

Address[1] = I2Address[2] = I3Address[3] = D

As the packet travels from I1 to I2:

Source Address = S Hdr Ext Len = 6Destination Address = I2 Segments Left = 2Destination Address = I2 Segments Left = 2

Address[1] = I1Address[2] = I3Address[3] = D

As the packet travels from I2 to I3:

Source Address = S Hdr Ext Len = 6Destination Address = I3 Segments Left = 1

Address[1] = I1Address[2] = I2Address[3] = D

As the packet travels from I3 to D:

Source Address = S Hdr Ext Len = 6Destination Address = D Segments Left = 0

Address[1] = I1Address[2] = I2Address[3] = I3

List of visited

nodes

Networking 35

Example of Lab Network

quadroporta

banc_3 b anc_6 pc3---[HUB]---pc2----+ +----pc2---[HUB]- --pc32000:0:0:3::/64 | | 2000:0:0:6 ::/64

| |banc_2 | | b anc_5banc_2 | | b anc_5pc3---[HUB]---pc2--[HUB]-+ +-[HUB]--pc2---[HUB]- --pc32000:0:0:2::/64 | | | | 2000:0:0:5 ::/64

| | | |banc_1 | | | | b anc_4pc3---[HUB]---pc2----+ | | +----pc2---[HUB]- --pc32000:0:0:1::/64 | | 2000:0:0:4 ::/64

| |2000:0:0:e::/64| |2000:0:0:d::/64

| |[routerv6]

2000:0:0:1::12000:0:0:1::aa 2000:0:0:e::1

Networking 36

Configuration examples in Linux

tux13:~# /sbin/ifconfig eth0 inet6 add 2000:0:0:1:: 1/64tux13:~# ifconfig eth0eth0 Link encap:Ethernet HWaddr 00:C0:DF:08:D 5:99

inet addr:172.16.1.13 Bcast:172.16.1.255 Mask:255 .255.255.0inet6 addr: 2000:0:0:1::1/64 Scope:Globalinet6 addr: fe80::2c0:dfff:fe08:d599/10 Scope:LinkUP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1RX packets:81403 errors:0 dropped:0 overruns:0 fram e:0TX packets:2429 errors:0 dropped:0 overruns:0 carri er:0TX packets:2429 errors:0 dropped:0 overruns:0 carri er:0collisions:0 txqueuelen:100RX bytes:4981344 (4.7 MiB) TX bytes:260692 (254.5 KiB)Interrupt:5

tux13:~# /sbin/route -A inet6 add 2000::/3 gw 2000 :0:0:1::aatux13:~# route -A inet6Kernel IPv6 routing tableDestination NextHop Flags M etric Ref Use Iface::1/128 :: U 0 0 0 lo2000:0:0:1::1/128 :: U 0 0 0 lo2000:0:0:1::/64 :: UA 2 56 0 0 eth02000::/3 2000:0:0:1::aa UG 1 0 0 eth0 fe80::2c0:dfff:fe08:d599/128 :: U 0 0 0 lofe80::/10 :: UA 2 56 0 0 eth0ff00::/8 :: UA 2 56 0 0 eth0::/0 :: UDA 2 56 0 0 eth0

Networking 37

Identifier IEEE EUI-64

Method to create a IEEE EUI-64 identifier from an I EEE 48bit MAC identifier. This is to insert two octets, with hexadecimal valu es of 0xFF and 0xFE, in the middle of the 48 bit MAC (between the compan y_id and vendor supplied id). For example, the 48 bit IEEE MAC with global scope:

|0 1|1 3|3 4 ||0 5|6 1|2 7 |+----------------+----------------+---------------- + |cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm||cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|+----------------+----------------+---------------- + 00:C0:DF:08:D5:99

where "c" are the bits of the assigned company_id, "0" is the value of the universal/local bit to indicate global scope, "g" i s individual/group bit, and "m" are the bits of the manufacturer-selected e xtension identifier. The interface identifier would be of the form:

|0 1|1 3|3 4 |4 6||0 5|6 1|2 7 |8 3|+----------------+----------------+---------------- +----------------+|cccccc1gcccccccc|cccccccc11111111|11111110mmmmmmmm |mmmmmmmmmmmmmmmm|+----------------+----------------+---------------- +----------------+

fe80::2c0:dfff:fe08:d599

Networking 38

Protocolo Neighbor Discovery (ND)

♦ IPv6 node uses ND for

» Find other nodes in the same link /LAN

» Find a node MAC address

ND substitutes ARP

» Find router(s) in its network

» Mantaining information about neighbour nodes

♦ ND similar to the IPv4 functions

» ARP IPv4

» ICMP Router Discovery

» ICMP Redirect

Networking 39

ND Messages

» ICMP messages (over IP); using Link Local addresses

» Neighbor Solicitation

Sent by a host to obtain MAC address of a neighbour / to verify its presence

» Neighbor Advertisement: Answer to the request» Neighbor Advertisement: Answer to the request

» Router Advertisement

Information about the network prefix; periodic or under request

Sent by router to IP address Link Local multicast

» Router Solicitation: host solicts from router a Router Advertisment message

» Redirect: Used by a router to inform na host about the best route to a destination

Networking 40

IPv6 Address Configuration

Networking 41

Packet Transmission