Chapter 6 Delivery and Routing of IP Packets. PDF created with FinePrint pdffactory Pro trial version

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1 Chapter 6 Delivery and Ruting f IP Packets PDF created with FinePrint pdffactry Pr trial versin

2 Outline Cnnectin Delivery Ruting methds Static and dynamic ruting Ruting table and mdule Classless addressing PDF created with FinePrint pdffactry Pr trial versin

3 6.1 CONNECTION-ORIENTED VERSUS CONNECTIONLESS SERVICES PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

4 Intrductin Delivery The physical frwarding f the packets Ruting Cnnectinless v.s. cnnectin-riented service Direct v.s. indirect delivery Finding the rute (next hp) fr a datagram Ruting methds Types f ruting, ruting tables and ruting mdule PDF created with FinePrint pdffactry Pr trial versin

5 Cnnectin-Oriented Versus Cnnectinless Services Delivery f a packet in the netwrk layer Cnnectin-riented Cnnectinless Cnnectin-riented the netwrk layer prtcl first makes a cnnectin between surce and destinatin befre sending a packet The decisin abut the rute f a sequence f packets is made nly ne When the cnnectin is established PDF created with FinePrint pdffactry Pr trial versin

6 6.1 Cnnectin-Oriented Versus Cnnectinless Services (Cnt.) Cnnectinless The netwrk layer treat each packet independently Each packet having n relatinship t any ther packet IP prtcl is a cnnectinless prtcl IP is an internetwrkprtcl and the packets may be delivered thrugh several hetergeneus netwrks Sme f the netwrk may nt be cnnectin-riented PDF created with FinePrint pdffactry Pr trial versin

7 6.2 DIRECT VERSUS INDIRECT DELIVERY The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

8 Direct Versus Indirect Delivery The delivery f a packet may be direct r indirect PDF created with FinePrint pdffactry Pr trial versin

9 Direct Delivery The final destinatin is a hst in the same physical netwrk as the deliverer When the surce and destinatin are lcated n the same physical netwrk Or the delivery is between the last ruter and the destinatin hst PDF created with FinePrint pdffactry Pr trial versin

10 Figure 6-1 Direct Delivery The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

11 Direct Delivery (Cnt.) Hw t determine if the delivery is direct Cmpare the netwrk addresses between the destinatin and the current netwrk Fr direct delivery, the sender uses the destinatin IP address t find the destinatin physical address Static methd: finding a table Dynamic methd: use the address reslutin prtcl (ARP) PDF created with FinePrint pdffactry Pr trial versin

12 Indirect Delivery The destinatin hst and the deliverer are nt n the same netwrk Packet ges frm ruters t ruters Fr indirect delivery The sender uses thedestinatin IP address and a ruting table t find the next ruter s IP address Then, the sender uses ARP prtcl t find the next ruter s physical address PDF created with FinePrint pdffactry Pr trial versin

13 Figure 6-2 Indirect Delivery The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

14 Indirect Delivery (Cnt.) A delivery always invlves ne direct delivery but zer r mre indirect deliveries Besides, the last delivery is always a direct delivery PDF created with FinePrint pdffactry Pr trial versin

15 6.3 ROUTING METHODS The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

16 Ruting Methds Ruting requires a hst/ruter t have a ruting table Hwever, with the increase f hsts, The number f entries in the ruting table als increase Lk fr ways t decrease the table size r handle issues such as security Next-hp ruting Netwrk-specific ruting Hst-specific ruting Default ruting PDF created with FinePrint pdffactry Pr trial versin

17 Next-Hp Ruting Hld nly the address f the next hp Instead f hlding infrmatin abut the cmplete rute PDF created with FinePrint pdffactry Pr trial versin

18 Figure 6-3 Next-Hp Ruting The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

19 Netwrk-Specific Ruting Use nly ne entry t define the address f the netwrk itself, i.e., netwrk address Instead f having an entry fr every hst cnnected t the same physical netwrk PDF created with FinePrint pdffactry Pr trial versin

20 Figure 6-4 Netwrk-Specific Ruting PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

21 Hst-Specific Ruting The destinatin hst address is given in the ruting table The inverse f netwrk-specific ruting Nt efficient fr perfrmance But, in sme ccasins, the administratr wants t have mre cntrl ver ruting Checking the rute Prviding security PDF created with FinePrint pdffactry Pr trial versin

22 Figure 6-5 Hst-SpecificRuting PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

23 Default Ruting Instead f listing all netwrks in the ruting table Just use ne entry called default Netwrk address is PDF created with FinePrint pdffactry Pr trial versin

24 Figure 6-6 Default Ruting The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

25 6.4 STATIC VERSUS DYNAMIC ROUTING The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

26 Static Versus Dynamic Ruting Table Static Ruting Table The entries are entered manually Cannt be updated unless manually altered by administratr Dynamic Ruting Table Update peridically using dynamic ruting prtcl RIP, OSPF, r BGP If a ruter shutdwn r a link is brken Update the tables accrdingly PDF created with FinePrint pdffactry Pr trial versin

27 6.5 ROUTING TABLE AND ROUTING MODULE PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

28 Ruting Table and Ruting Mdule When lk fr the rute First check fr direct delivery Then hst-specific delivery Then netwrk-specific delivery Finally default delivery This hierarchical strategy can be implemented in the ruting mdule r in the ruting table PDF created with FinePrint pdffactry Pr trial versin

29 Figure 6-7 Ruting Mdule and Ruting Table PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

30 Ruting Table Ruting table usually has seven fields Mask, destinatin address, next-hp address, flags, reference cunt, use, and interface Mask: applies t the destinatin IP address t find the netwrk/subnetwrk address f the destinatin In hst-specific ruting: mask = In default ruting: mask = In an unsubnettednetwrk: mask = default mask PDF created with FinePrint pdffactry Pr trial versin

31 Ruting Table (Cnt.) Destinatin address: can be either Destinatin hst address (hst-specific address) Destinatin netwrk address (netwrk-specific address) Next-hp address The address f the next-hp ruter PDF created with FinePrint pdffactry Pr trial versin

32 Ruting Table (Cnt.) Flags U (Up): the ruter is up and running. If nt present, cannt frward packet t this ruter G (Gateway): destinatin is in anther netwrk and use indirect delivery If nt present, use direct delivery H (Hst-specific): the entry in the destinatin field is hst-specific address If nt present, destinatin field is netwrk-specific address PDF created with FinePrint pdffactry Pr trial versin

33 Ruting Table (Cnt.) Flags D (Added by redirectin): ruting infrmatin fr this destinatin has been added by a redirectin message frm ICMP. M (Mdified by redirectin): ruting infrmatin fr this destinatin has been mdified by a redirectin message frm ICMP. Discuss in Chapter 9 PDF created with FinePrint pdffactry Pr trial versin

34 Ruting Table (Cnt.) Reference cunt The number f users that are using this rute at any mment Use The number f packets transmitted thrugh this ruter fr the crrespnding destinatin Interface The name f interface PDF created with FinePrint pdffactry Pr trial versin

35 Figure 6-8 Ruting Table Flags U G H D M The ruter is up and running. The destinatin is in anther netwrk. Hst-specific address. Added by redirectin. Mdified by redirectin. PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

36 Ruting Mdule 1. Fr each entry in the ruting table 1. Apply the mask t the packet dest. Address 2. If ( the result match the value in the dest. field) 1. If (the G flag is present) // indirect delivery 1. Use the next-hp entry in the table as next-hp address 2. If (the G flag is missing) 1. Use packet destinatin address (direct delivery) 3. Send packet t fragmentatin mdule with next-hp address 4. Stp 2. If n match is fund, send an ICMP errr message 3. Stp PDF created with FinePrint pdffactry Pr trial versin

37 Figure 6-9 Cnfiguratin fr Ruting Example PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

38 Ruting Table f R1 Used fr Example Mask Dest. Next Hp F I U m U m U m UGH m UG m UG m UG m0 PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

39 Example 1 Ruter R1 receives 500 packets fr destinatin ; the algrithm applies the masks rw by rw t the destinatin address until a match (with the value in the secnd clumn: Destinatin field) is fund: PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

40 Slutin Direct delivery & Ł n match & Ł n match & Ł n match Hst-specific & Ł n match Netwrk-specific & Ł match PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

41 Slutin The ruter send the packet thrugh interface m0 Increment the use field by 500 Increase the reference cunt field by 1 PDF created with FinePrint pdffactry Pr trial versin

42 Example 2 Ruter R1 receives 100 packets fr destinatin ; the algrithm applies the masks rw by rw t the destinatin address until a match is fund: PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

43 Slutin Direct delivery & Ł n match & Ł match The ruter send the packet thrugh interface m2 alng with the next-hp IP address Increment the use field by 100 Increase the reference cunt field by 1 PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

44 Example 3 Ruter R1 receives 20 packets fr destinatin ; the algrithm applies the masks rw by rw t the destinatin address until a match is fund: PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

45 Slutin Direct delivery & Ł n match & Ł n match & Ł n match Hst-specific & Ł n match PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

46 Slutin Netwrk-specific & Ł n match & Ł n match Default & Ł match The ruter send the packet thrugh interface m0 alng with the next-hp IP address Increment the use field by 20 Increase the reference cunt field by 1 PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

47 Example 4 Make the ruting table fr ruter R1 in the fllwing Figure PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

48 Example 4 There are three explicit destinatin netwrks and ne default access t the rest f the Internet (default rute) The netwrk is direct ruting G is nt present and Next Hp is blank Anther three netwrks are indirect ruting G = 1 and Next Hp given the IP address f next hp The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

49 Slutin Mask Destinatin Next Hp I m m m m0 PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

50 Example 5 Make the ruting table fr ruter R1 in Figure 6.11 PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

51 Example 5 There are five netwrk, but tw f them are pint-tpint with n hsts and need nt be in the ruting table There is als an entry fr the default rute But we d nt knw the IP address t the default rute. The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

52 Slutin Mask Destinatin Next Hp I m m1 r r m m1 r r m ???????????? m0 PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

53 Example 6 The ruting table fr ruter R1 is given belw. Draw its tplgy Mask Destinatin Next Hp I m m m m m m0 PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

54 Figure 6-12 Example6: Slutin Frm the table: There are three netwrks directly cnnected t R1 There are tw netwrks indirectly cnnected t R1 One default ruter t the rest f netwrk Hwever, we d nt knw whether the netwrk and are Directly cnnected t the ruter R2 Or thrugh a pint-t-pint netwrk and anther ruter The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

55 6.6 CLASSLESS ADDRESSING: CIDR The McGraw-Hill Cmpanies, Inc., 2000 PDF created with FinePrint pdffactry Pr trial versin

56 Classless Addressing Requires changes as cmpared t the classful addressing Ruting Table Size Hierarchical Ruting Gegraphical Ruting Ruting Table Search Algrithms PDF created with FinePrint pdffactry Pr trial versin

57 Ruting Table Size In classfuladdress There is nly ne entry fr each site Even this site is subnetted In classless address The number f entries can either decrease r increase PDF created with FinePrint pdffactry Pr trial versin

58 Ruting Table Size (Cnt.) Decrease In classful addressing Fur entries in the ruting table fr an rganizatin that creates a supernet frm fur class C blcks In classless addressing Only ne entry in the ruting table Increase: mre likely ccur Class A and B blcks are divided int smaller blcks in classless addressing PDF created with FinePrint pdffactry Pr trial versin

59 Hierarchical Ruting T slve the prblem f vast ruting tables Create a sense f hierarchy in the Internet architecture and ruting tables Internet is divided int internatinal and natinal ISP Natinal ISP are divided int reginal ISPs Reginal ISP are divided int lcal ISPs Ruting table decrease its size by this hierarchical structure PDF created with FinePrint pdffactry Pr trial versin

60 Gegraphical Ruting T decrease the size f the ruting table even further, we need t extend hierarchical ruting t include gegraphical ruting Divide the entire address space int a few large blcks A blck t Nrth America A blck t Eurpe A blck t Asia A blck t Africa PDF created with FinePrint pdffactry Pr trial versin

61 Ruting Table Search Algrithm Previus, the ruting table is rganized as a list Hwever, t make search easier, the ruting table can be divided int three buckets (areas) When a packet arrives, applies the default mask t find the crrespnding bucket (class A, B, r C) Ntably, frm a address, we can derive which class it belngs t PDF created with FinePrint pdffactry Pr trial versin

62 Ruting Table Search Algrithm (Cnt.) In classless ruting, we can als use buckets Hwever, 32 buckets are used instead f three Each buckets crrespnding t each prefix length When a packet arrives, try the lngest prefix (/32), then the next prefix (/31) and s n until matched Lngest match methd Hwever, this search methd wuld als take quite a lng time Use ther data structures such as tree r binary tree PDF created with FinePrint pdffactry Pr trial versin

63 In classful addressing, each address has self-cntained infrmatin that facilitates ruting table searching. PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000

64 In classless addressing, there is n self-cntained infrmatin in the destinatin address t facilitate ruting table searching. PDF created with FinePrint pdffactry Pr trial versin The McGraw-Hill Cmpanies, Inc., 2000