Mobile Communications. Fundamental Networking

Transcription

1 Networking 1 Mobile Communications Fundamental Networking Manuel P. Ricardo Faculdade de Engenharia da Universidade do Porto

2 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 are the differences between IPv6 and IPv4?

3 Networking 3 Switching: Circuits, Virtual Circuits, Datagram

4 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

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

6 Networking 6 Packet Switching Technologies: Ethernet, IP Path defined by packet destination address

7 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?

8 Networking 8 L2 Networking Frame Formats 7x Protocolo=IP Ethernet Bit stuffing 5 1s seguidos Ł emissor introduz 0 PPP

9 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» 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

10 Networking 10 L2 Networking - Single Tree Required Ethernet frame No hop-count Could loop forever in a L2 misconfigured 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

11 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

12 Networking 12 Virtual LANs One bridge simulates multiple LANs / broadcast domains One LAN may be extended to other bridges w x [da=w; sa=x; data] [da=w; sa=x; data] VLAN 100 VLAN 100 VLAN 200 B 1 B 2 VLAN 200 y z [da=w; sa=x; vlanid=100; data]

13 Networking 13 L3 Networking Packet Formats Version HLen TOS Length Version Traffic Class Flow Label Ident Flags Offset Payload Lengtht Next Header Hop Limit TTL Protocol Checksum SourceAddr SourceAddr (4 words) DestinationAddr Options (variable) Data Pad (variable) DestinationAddr (4 words) Options (variable number) Data IPv4 IPv6

14 Networking 14 L3 Networking Router 3ª generation router

15 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» Helps routers build their SPT» RIP, OSPF, BGP A F B E C G D B s routing view Destination Cost NextHop A 1 A C 1 C D 2 C E 2 A F 2 A G 3 A

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

17 Networking 17 Multimedia Traffic - Taxonomy Applications Elastic Real time (variation of the packet end-to-end delay) Intolerant Tolerant (packet loss) Nonadaptive Adaptive (application reaction to packet loss) Rate adaptive Delay adaptive (type of reaction)

18 Networking 18 RTP+RTCP/UDP Multimedia traffic Application-Level Framing Data Packets (RTP)» sequence number» 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

19 Networking 19 Traditional TCP/IP Communications Stack IETF IP address based switching APP TCP IP T1 T1 T2 IP T2 T3 IP T3 T4 T4 T5 APP TCP IP T5 host bridge router router bridge host IEEE MAC address based switching

20 Networking 20 Tunnel IP-in-IP APP TCP IP IP T1 T1 T2 IP T2 T3 IP IP T3 T4 T4 T5 APP TCP IP T5 H1 bridge R1 R2 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

21 Networking 21 Tunnel PPP over IP (E.g PPTP) APP TCP IP PPP GRE IP T1 T1 T2 IP T2 T3 IP PPP GRE IP T3 T4 T4 T5 APP TCP IP T5 H1 bridge R1 R2 bridge Server» GRE virtual point-to-point link routers at remote points over an IP network» PPP adequate for Authentication Transporting IP packets

22 PPP over Ethernet Networking 22

23 IPv6 Networking 23

24 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

25 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

26 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: or :: Loopback address: ::1 Network prefix described by /, same as IPv4» FEDC:BA98:7600::/40 network prefix = 40 bits

27 Networking 27 Reserved Addresses Allocation Prefix Fraction of (binary) Address Space Unassigned /256 Unassigned /256 Reserved for NSAP Allocation /128 Unassigned /64 Unassigned /32 Unassigned /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 /16 Unassigned /32 Unassigned /64 Unassigned /128 Unassigned /512 Link-Local Unicast Addresses /1024 Site-Local Unicast Addresses /1024 Multicast Addresses /256

28 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» Global Unicast Global addresses Address: network prefix + computer identifier Structured prefixes» Anycast Network aggregation; less entries in the forwarding tables 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

29 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 bits 54 bits 64 bits Link-Local Unicast address (fe80::/10) interface ID bits 54 bits 64 bits Site-Local Unicast address (fec0::/10) subnet ID interface ID n bits 128-n bits Anycast address subnet prefix bits flgs scop group ID Multicast address Scope link, site, global,... (ff::/8)

30 Networking 30 Headers IPv4 and IPv Version HLen TOS Length Version Traffic Class Flow Label Ident Flags Offset Payload Lengtht Next Header Hop Limit TTL Protocol Checksum SourceAddr SourceAddr (4 words) DestinationAddr Options (variable) Data Pad (variable) DestinationAddr (4 words) Options (variable number) Data IPv4 IPv6

31 Networking 31 IPv6 Header Flow label identifies packet flow» QoS, resource reservation» Packets receive same service Version Traffic Class Flow Label Payload Lengtht Next Header Hop Limit Payload length» Header not included Hop limit = TTL (v4) SourceAddr (4 words) DestinationAddr (4 words) Options (variable number) Data Next header» Identifies next header/extension Options included as extension headers

32 Networking 32 Extension Headers IPv6 Header Next Header = TCP TCP header + data IPv6 Header Next Header = Routing Routing Header Next Header = TCP TCP header + data IPv6 Header Next Header = Routing Routing Header Fragment Header Next Header = Fragment Next Header = TCP Fragment of TCP header + data IPv6 Hop-by-hop Destination Routing Fragment Authenticate. ESP TCP

33 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» 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

34 Routing Header - Pacote sent from S to D, through I1, I2, I3 Networking 34 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 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

35 Networking 35 Example of Lab Network quadro porta banc_3 banc_6 pc3---[hub]---pc pc2---[hub]---pc3 2000:0:0:3::/ :0:0:6::/64 banc_2 banc_5 pc3---[hub]---pc2--[hub]-+ +-[HUB]--pc2---[HUB]---pc3 2000:0:0:2::/ :0:0:5::/64 banc_1 banc_4 pc3---[hub]---pc pc2---[hub]---pc3 2000:0:0:1::/ :0:0:4::/ :0:0:e::/ :0:0:d::/64 [routerv6] 2000:0:0:1::1 2000:0:0:1::aa 2000:0:0:e::1

36 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: Bcast: Mask: 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 collisions:0 txqueuelen:100 RX bytes: (4.7 MiB) TX bytes: (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 lo 2000:0:0:1::1/128 :: U lo 2000:0:0:1::/64 :: UA eth0 2000::/3 2000:0:0:1::aa UG eth0 fe80::2c0:dfff:fe08:d599/128 :: U lo fe80::/10 :: UA eth0 ff00::/8 :: UA eth0 ::/0 :: UDA eth0

37 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: cccccc0gcccccccc ccccccccmmmmmmmm mmmmmmmmmmmmmmmm :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: cccccc1gcccccccc cccccccc mmmmmmmm mmmmmmmmmmmmmmmm fe80::2c0:dfff:fe08:d599

38 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

39 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» 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

40 IPv6 Address Configuration Networking 40

41 Packet Transmission Networking 41