ETSF05 Internetprotokoll. Jens Andersson

Transkript

1 ETSF05 Internetprotokoll PPP, NAT, IPv6, Go Back N Routing och Routingalgoritmer Föreläsning 1 Jens Andersson

2 Nätmodellen applikation transport nät länk fysisk länk applikationsprotokoll transportprotokoll applikation transport nät länk fysisk länk 2

3 Sändarsidan applikation AH S transport TH S AH S data nät NH S TH S AHdata S länk LH S NH S TH S data AH S fysisk länk

4 Datapaket När data skall skickas mellan två datorer delas den (oftast) t)först upp i mindre dl delar, så klld kallade paket. kt Ett paket består av upp till tre delar: huvud, data och svans huvud (header) data (payload) svans (tail) Huvud och svans innehåller kontrollinformation. 4

5 PPP Point to Point Protocol Bygger på HDLC Generellt Kan användas för olika nätprotokoll Olika stödprotokoll Autentisering Länkkontroll (kontroll på länknivån) Nätkontroll (kontroll på nätnivån) 4.5

6 Figure PPP frame format 11.6

7 Figure Multiplexing in PPP 11.7

8 Figure LCP packet encapsulated in a frame 11.8

9 Table 11.2 LCP packets 11.9

10 11.10 Table 11.3 Common options

11 Figure PAP packets encapsulated in a PPP frame 11.11

12 Figure CHAP packets encapsulated in a PPP frame 11.12

13 Figure IPCP packet encapsulated in PPP frame 11.13

14 11.14 Table 11.4 Code value for IPCP packets

15 Figure IP datagram encapsulated in a PPP frame 11.15

16 Figure Multilink PPP 11.16

17 Figure An example 11.17

18 Figure An example (continued) 11.18

19 Figure Transition phases 11.19

20 NAT Network Address Translation Räddar Internet från adressbrist Möjligt återanvända IP adresser Ändrar IP adresser/tcp&udp portar i paket 4.20

21 19.21 Table 19.3 Addresses for private networks

22 Figure A NAT implementation 19.22

23 Figure Addresses in a NAT 19.23

24 Figure NAT address translation Alternative: External Source Address goes here 19.24

25 Table 19.4 Five-column translation table Alternative: External source address goes here Alternative: External source port goes here

26 Figure An ISP and NAT Hemmanätet tilldelas oftast 1 extern adress 19.26

27 IPv4 adresser tar slut IPv6 232 adresser Orättvist fördelade i världen Variabel header IPv adresser Konceptet flöde (både TCP och UDP) Fast theaderstorlek Kolla fragmentering redan vid källan 4.27

28 Figure IPv6 address in binary and hexadecimal colon notation 19.28

29 Figure Abbreviated IPv6 addresses 19.29

30 Table 19.5 Type prefixes for IPv6 addresses 19.30

31 Table 19.5 Type prefixes for IPv6 addresses (continued) 19.31

32 Figure Prefixes for provider-based unicast address 19.32

33 Figure Multicast address in IPv

34 Figure Reserved addresses in IPv

35 Figure Local addresses in IPv

36 Go Back N ARQ Repetion Behövs när vi diskuterar TCP i nästa lp 4.36

37 Figure Design of Go-Back-N ARQ 11.37

38 Figure Send window for Go-Back-N ARQ 11.38

39 Figure Receive window for Go-Back-N ARQ 11.39

40 Figure Flow diagram for Example

41 Figure Flow diagram for Example

42 Figure Window size for Go-Back-N ARQ 11.42

43 Routing och routingalgoritmer Distance Vector Routing Link State Routing 4.43

44 Network protocol operation

45 Task: Choosing an Optimal Path R1 R4 5 R R6 6 5 B R2 15 A R8 R3 5 R5 10

46 Routing Technologies No intelligence Centralized Distributed

47 Flooding Forward packet on all outgoing interfaces Exclude incoming interface Hop count prevents looping B 47

48 Centralized routing technology Database and algorithm centralized Network equipment informs central function Packet forwarding distributed of course!?

49 Distributed routing technology Routing process distributed ib d among all routers Two approaches Distance Vector Each nodes best path information is distributed to its neighbours Best end to end paths result from composition of all next hop choices Simple, low demands on processor and memory Link State Local topology information is flooded to all nodes Best end to endpaths arecomputed locally at eachrouter More complicated, high demands on processor and memory

50 Least hop path Path with least numbor of hops is best A B C D E 50

51 Least cost path Best path is path with least aggregated cost A 2 B 3 C D 3 E 51

52 The Link Metric Possible metrics hop count inverse of the link bandwidth dl delay dynamically calculated administratively assigned combination

53 Distance vector routing

54 Link state routing

55 Figure Example of an Internet

56 Figure The Concept of Distance Vector Routing

57 Figure Distance Vector Routing Tbl Table

58 Figure Routing Table Distribution

59 Figure Updating Routing Table for Router A

60 Figure Final Routing Tables

61 Updating Algorithm (1) if (d (advertised ddestination i not in table) then update table (2) else (2.a) if (advertised next hop = next hop in table) then replace entry (2.b) else (2.b.i) if (advertised hop count < hop count intable) then replace entry (2.b.ii) else do nothing

62 Figure Example 21.1 Net2: Replace (Rule 2.a) Net3: Add (Rule 1) Net6: Replace (Rule 2.b.i) Net8: No change (Rule 2.b.ii) Net9: No change (Rule 2.b.ii)

63 Figure Concept of Link State Routing

64 Figure Cost tin Link State t Routing

65 Figure Link StatePacket

66 Figure Flooding of As A s LSP

67 Figure Link State Database

68 The Dijkstra Algorithm 1. Identify the root (the node itself) 2. Attach all neighbour nodes temporarily 3. Make arc and node with least cumulative cost permanent 4. Choose this node 5. Repeat 2 and 3 until all nodes are permanent

69 Figure Costs in the Dijkstra Algorithm

70 1. Identify the root (the node itself) 2. Attach all neighbour nodes temporarily 3. Mk Make arc and node with ithleast cumulative lti cost permanent 4. Choose this node 5. Repeat 2 and 3 until all nodes are permanent

71 Figure 21 30, Part I Shortest Path Calculation, Part I

72 Figure 21 30, Part II Shortest Path Calculation, Part II

73 Figure 21 31, Part XIII Shortest Path Calculation, Part XIII

74 Figure Routing Table for Router A