Mobile Communications Fundamental Networking Manuel P. Ricardo - - PowerPoint PPT Presentation

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

Tabela de translação de portas / canais virtuais 1 M a t 1 N 2 t Entrada M a b c y z c 1 N 2 2 1 N k h m n n g 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 k n 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

PPP

Bit stuffing – 5 1s seguidos Ł Ł Ł Ł 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 port

Ł 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 frame forwarded to that port – If not 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 x w 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 4 8 16 19 31 Version

Traffic Class

Flow Label Payload Lengtht Next Header Hop Limit SourceAddr (4 words) 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 adaptive Rate 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

• uter IP header inner IP header

data

DA= 2nd IP address of R2 SA= 2nd IP address of H1 TTL IP identification IP-in-IP IP checksum flags fragment offset length TOS ver. IHL DA= Server SA=H1 TTL IP identification

• lay. 4 prot.

IP checksum flags fragment offset length TOS ver. 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 GRE GRE 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

IPv6 IPv6

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

• 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

• network prefix = 40 bits

Networking 27

Reserved Addresses

Allocation Prefix Fraction of (binary) Address Space

• Unassigned

0000 0000 1/256 Unassigned 0000 0001 1/256 Reserved for NSAP Allocation 0000 001 1/128 Unassigned 0000 01 1/64 Unassigned 0000 1 1/32 Unassigned 0001 1/16 Unassigned 0001 1/16 Global Unicast 001 1/8 Unassigned 010 1/8 Unassigned 011 1/8 Unassigned 100 1/8 Unassigned 101 1/8 Unassigned 110 1/8 Unassigned 1110 1/16 Unassigned 1111 0 1/32 Unassigned 1111 10 1/64 Unassigned 1111 110 1/128 Unassigned 1111 1110 0 1/512 Link-Local Unicast Addresses 1111 1110 10 1/1024 Site-Local Unicast Addresses 1111 1110 11 1/1024 Multicast 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 | interface ID | +------------------------+-----------+----------------------------+ | 10 | | bits | 54 bits | 64 bits | Link-Local Unicast address +----------+-------------------------+----------------------------+ (fe80::/10) |1111111010| 0 | interface ID | +----------+-------------------------+----------------------------+ | 10 | | bits | 54 bits | 64 bits | Site-Local Unicast address +----------+-------------------------+----------------------------+ (fec0::/10) |1111111011| subnet ID | interface ID | +----------+-------------------------+----------------------------+ | n bits | 128-n bits | Anycast address +------------------------------------------------+----------------+ | subnet prefix | 00000000000000 | +------------------------------------------------+----------------+ | 8 | 4 | 4 | 112 bits | +------ -+----+----+---------------------------------------------+ |11111111|flgs|scop| group ID | +--------+----+----+---------------------------------------------+

Multicast address Scope – link, site, global, ... (ff::/8)

Networking 30

Headers IPv4 and IPv6

Version HLen TOS Length Ident Flags Offset TTL Protocol Checksum SourceAddr 4 8 16 19 31 Version

Traffic Class

Flow Label Payload Lengtht Next Header Hop Limit SourceAddr (4 words) 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 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) 4 8 16 24 31

♦ Payload length

» Header not included

♦ Hop limit = TTL (v4) ♦ Next header

» Identifies next header/extension

♦ Options included as extension headers

DestinationAddr (4 words) Options (variable number) Data

Networking 32

Extension Headers

IPv6 Header

Next Header = TCP

TCP header + data Routing Header

Next Header = TCP

TCP header + data IPv6 Header

Next Header = Routing

IPv6 Header

Next Header = Routing

Routing Header

Next Header = Fragment

Fragment Header

Next Header = TCP

Fragment of TCP header + data IPv6 Hop-by-hop TCP Destination 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, I3

As the packet travels from S to I1: Source Address = S Hdr Ext Len = 6 Destination Address = I1 Segments Left = 3 Address[1] = I2 Address[2] = I3 Address[3] = D As the packet travels from I1 to I2: Source Address = S Hdr Ext Len = 6 Destination Address = I2 Segments Left = 2 Destination Address = I2 Segments Left = 2 Address[1] = I1 Address[2] = I3 Address[3] = D As the packet travels from I2 to I3: Source Address = S Hdr Ext Len = 6 Destination Address = I3 Segments Left = 1 Address[1] = I1 Address[2] = I2 Address[3] = D As the packet travels from I3 to D: Source Address = S Hdr Ext Len = 6 Destination Address = D Segments Left = 0 Address[1] = I1 Address[2] = I2 Address[3] = I3

List of visited nodes

Networking 35

Example of Lab Network

quadro porta banc_3 banc_6 pc3---[HUB]---pc2----+ +----pc2---[HUB]---pc3 2000:0:0:3::/64 | | 2000:0:0:6::/64 | | banc_2 | | banc_5 banc_2 | | banc_5 pc3---[HUB]---pc2--[HUB]-+ +-[HUB]--pc2---[HUB]---pc3 2000:0:0:2::/64 | | | | 2000:0:0:5::/64 | | | | banc_1 | | | | banc_4 pc3---[HUB]---pc2----+ | | +----pc2---[HUB]---pc3 2000:0:0:1::/64 | | 2000:0:0:4::/64 | | 2000:0:0:e::/64| |2000:0:0:d::/64 | | [routerv6] 2000:0:0:1::1 2000:0:0:1::aa 2000:0:0:e::1

Networking 36

Configuration examples in Linux

tux13:~# /sbin/ifconfig eth0 inet6 add 2000:0:0:1::1/64 tux13:~# ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:C0:DF:08:D5:99 inet addr:172.16.1.13 Bcast:172.16.1.255 Mask:255.255.255.0 inet6 addr: 2000:0:0:1::1/64 Scope:Global inet6 addr: fe80::2c0:dfff:fe08:d599/10 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:81403 errors:0 dropped:0 overruns:0 frame:0 TX packets:2429 errors:0 dropped:0 overruns:0 carrier:0 TX packets:2429 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX 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::aa tux13:~# route -A inet6 Kernel IPv6 routing table Destination NextHop Flags Metric Ref Use Iface ::1/128 :: U 0 0 0 lo 2000:0:0:1::1/128 :: U 0 0 0 lo 2000:0:0:1::/64 :: UA 256 0 0 eth0 2000::/3 2000:0:0:1::aa UG 1 0 0 eth0 fe80::2c0:dfff:fe08:d599/128 :: U 0 0 0 lo fe80::/10 :: UA 256 0 0 eth0 ff00::/8 :: UA 256 0 0 eth0 ::/0 :: UDA 256 0 0 eth0

Networking 37

Identifier IEEE EUI-64

Method to create a IEEE EUI-64 identifier from an IEEE 48bit MAC identifier. This is to insert two octets, with hexadecimal values of 0xFF and 0xFE, in the middle of the 48 bit MAC (between the company_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" is individual/group bit, and "m" are the bits of the manufacturer-selected extension 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