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 a b c c k n k b a 1 1 Entrada Saída comutação n m espacial 2 Porta CV Porta CV a 2 n 1 comutação b 1 n y c z y g h g M N c N g de etiqueta t t y 1 k M cabeçalho z N h controlo de c 2 m dados comutação a, b, c, ... indicador de canal virtual Tabela de translação de portas / canais virtuais

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 7x 10101010 10101011 Protocolo=IP Ethernet Bit stuffing – 5 1s seguidos Ł emissor introduz 0 Ł Ł Ł PPP

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 w x x [da=w; sa=x; data] [da=w; sa=x; data] VLAN 100 VLAN 100 B 1 B 2 VLAN 200 VLAN 200 y z [da=w; sa=x; vlanid=100 ; data]

Networking 13 L3 Networking – Packet Formats 0 4 8 16 24 31 0 4 8 16 19 31 Flow Label TOS Length Version Traffic Class Version HLen Ident Flags Offset Payload Lengtht Next Header Hop Limit TTL Protocol Checksum SourceAddr (4 words) SourceAddr SourceAddr DestinationAddr DestinationAddr (4 words) Pad Options (variable) (variable) Options (variable number) Data 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 B’s routing view Destination Cost NextHop B A 1 A C A C 1 C D D 2 C E E 2 A F 2 A G F G 3 A

Networking 16 TCP ♦ Point to connection between a client and a server; port-to-port (SequenceNum) Data ♦ Reliable, flow control Sender Receiver Acknowledgment + AdvertisedWindow AdvertisedWindow ♦ Congestion control

Networking 17 Multimedia Traffic - Taxonomy Applications Real time (variation of the packet end-to-end delay) Elastic (packet loss) Intolerant Tolerant (application reaction to packet loss) Nonadaptive Adaptive Rate adaptive Delay adaptive (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 APP APP TCP TCP IP IP IP IP T1 T1 | T2 T3 | T4 T4 | T5 T5 T2 | T3 host router router bridge bridge host IEEE MAC address based switching

Networking 20 Tunnel IP-in-IP APP TCP APP IP TCP IP IP IP IP IP T4 | T5 T1 T1 | T2 T2 | T3 T3 | T4 T5 H1 R2 bridge R1 bridge Server outer IP header inner IP header data ver. IHL TOS length IP identification flags fragment offset TTL IP-in-IP IP checksum SA= 2nd IP address of H1 DA= 2nd IP address of R2 ver. IHL TOS length IP identification flags fragment offset TTL lay. 4 prot. IP checksum SA=H1 DA= Server TCP/UDP/ ... payload

Networking 21 Tunnel PPP over IP (E.g PPTP) APP TCP IP IP PPP PPP APP GRE GRE TCP IP IP IP IP T1 T3 | T4 T4 | T5 T5 T1 | T2 T2 | T3 H1 R2 R1 bridge bridge Server » 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 Address Representation ♦ 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 � � ♦ 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