COMPUTER NETWORK DESIGN Network layer protocols

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1 OMPUTER NETWORK ESIGN Network lyer protools Network lyer (lyer 3) Gruppo Reti TL OMPUTER NETWORK ESIGN Review of network lyer protools - opyright This work is liensed under the retive ommons Noerivs-Nonommeril Liense. To view opy of this liense, visit: or send letter to retive ommons, 559 Nthn ott Wy, Stnford, liforni 9435, US. knowledgements Some pitures/slides tken from Kurose Ross omputer Networking OMPUTER NETWORK ESIGN Review of network lyer protools - Network lyer funtions Routing Exeuted looking t routing tles For every PU in pket swithing with dtgrm servie (IP) For every virtul iruit opening request (signlling) Routing tle ontin For every destintion the next-hop router Three elements Routing protools Routing lgorithms Forwrding rules ddressing Uniqueness ddress trnsltion ongestion ontrol (disussed lter) OMPUTER NETWORK ESIGN Review of network lyer protools - 3 Network lyer In the Internet Pket swithing with dtgrm servie IP protool (RF 79) defines Pket formt ddresses Forwrding proedures IP provide est effort servie onnetionless Stteless pproh Unrelile No QoS gurntees lthough some priority its in the pket heder re defined OMPUTER NETWORK ESIGN Review of network lyer protools - 4 IP pket heder Version HLEN Servie Type Totl Length Identifition Flgs Frgment Offset Time To Live Protool Heder heksum Soure IP ddress estintion IP ddress Options P Frgmenttion MTU (Mximum Trnsfer Unit): mximum dtgrms zie (inluding heder) on link epends on lyer protool If the MTU on link does not permit the pket trnsmission Frgmenttion needed Frgments eome independent dtgrms, with similr heder to the originl dtgrm Frgmenttion fields, length, heder heksum re modified Stndrd size: yte OMPUTER NETWORK ESIGN Review of network lyer protools - 5 OMPUTER NETWORK ESIGN Review of network lyer protools - 6 Pg.

2 OMPUTER NETWORK ESIGN Network lyer protools Frgmenttion The re-ssemly of the originl dtgrm from the frgments is done only t the reeiving host (never in routers) Frgmenttion must e trnsprent to lyer 4 Frgmenttion is hrmful More overhed One frgment lost implies the whole pket dropped Higher loss proility Timer needed t the reeiver for re-ssemly purposes OMPUTER NETWORK ESIGN Review of network lyer protools - 7 IP ddressing: introdution IP ddress: 3-it identifier for host, router interfe Interfe onnetion etween host/router nd physil link router s typilly hve multiple interfes host typilly hs one interfe IP ddresses ssoited with eh interfe = OMPUTER NETWORK ESIGN Review of network lyer protools - 8 Sunets Sunets IP ddress: sunet prt (high order its) host prt (low order its) Wht s sunet? devie interfes with sme sunet prt of IP ddress n physilly reh eh other without intervening router sunet network onsisting of 3 sunets OMPUTER NETWORK ESIGN Review of network lyer protools - 9 OMPUTER NETWORK ESIGN Review of network lyer protools - IP ddressing: IR IR: lssless Interomin Routing sunet portion of ddress of ritrry length ddress formt:...d/x, where x is # its in sunet portion of ddress sunet prt.3.6./3 host prt IP ddresses ssignments host gets n IP ddress By onfigurtion Stti ssignment Vi server through the HP: ynmi Host onfigurtion Protool Stti or dynmi ssignment Potentil to re-use ddresses network gets the sunet prt By n lloted portion of its provider ISP s ddress spe ISP's lok.3.6./ Orgniztion.3.6./3 Orgniztion.3.8./3 Orgniztion.3../ Orgniztion /3 OMPUTER NETWORK ESIGN Review of network lyer protools - OMPUTER NETWORK ESIGN Review of network lyer protools - Pg.

3 OMPUTER NETWORK ESIGN Network lyer protools Hierrhil ddressing for route ggregtion Hierrhil ddressing llows effiient dvertisement of routing informtion Redue routing tle size Orgniztion.3.6./3 Orgniztion.3.8./3 Orgniztion.3../3 Orgniztion /3. Fly-By-Night-ISP ISPs-R-Us Send me nything with ddresses eginning.3.6./ Send me nything with ddresses eginning /6 Internet Hierrhil ddressing: more speifi routes ISPs-R-Us hs more speifi route to Orgniztion Orgniztion.3.6./3 Orgniztion.3../3 Orgniztion /3 Orgniztion.3.8./3. Fly-By-Night-ISP ISPs-R-Us Send me nything with ddresses eginning.3.6./ Send me nything with ddresses eginning /6 or.3.8./3 Internet OMPUTER NETWORK ESIGN Review of network lyer protools - 3 OMPUTER NETWORK ESIGN Review of network lyer protools - 4 Routing protools nd lgorithms Gruppo Reti TL nome.ognome@polito.it Routing Routing protool How info on network sttus re exhnged mong routers to uild routing tles Routing lgorithm Rules to follow to define the est pths(s) towrd speifi destintion retes routing tles Forwrding proedure tions needed to move pkets from input to the proper output port Exploits routing tle OMPUTER NETWORK ESIGN Review of network lyer protools - 5 OMPUTER NETWORK ESIGN Review of network lyer protools - 6 Routing lgorithms Gol: efine good pth (sequene of link/nodes) from the soure to the destintion Every node () represents ll the soure/destintion onneted to it On the grph representing the network topology ost re ssoited to edges 5 Good pth 3 B 5 Minimum ost pth 3 E F ost Unitry ost, distne, dely, ongestion level, lod Stti or dynmi (network stte dependent) Influenes updte poliies Risk of osilltions Exmple: ost relted to link lod +e B e e Initil sitution +e +e B +e B +e pth reomputtion reomputtion +e +e B reomputtion OMPUTER NETWORK ESIGN Review of network lyer protools - 7 OMPUTER NETWORK ESIGN Review of network lyer protools - 8 Pg. 3

OMPUTER NETWORK ESIGN Network lyer protools Routing lgorithms: exmples No oordintion mong nodes needed Rndom Rndomly selet one output port Flooding Mke opy nd forwrd to ll output ports efletion or

4 OMPUTER NETWORK ESIGN Network lyer protools Routing lgorithms: exmples No oordintion mong nodes needed Rndom Rndomly selet one output port Flooding Mke opy nd forwrd to ll output ports efletion or hot potto Normlly used on regulr topologies Mny good pths towrd the destintion If proper output port ville, rooute. Otherwise hoose nother port None requires uffering (uffering on the link) Esy ut performne degrdtion istriuted routing protools Tody more used thn entrlized lthough entrlized routing is gining inresing interest (SN pprohes) Two fmilies, relying on : Glol info: Known topology to eh node through info exhnge mong ll nodes Run grph trversl lgorithm to define routing tle Link stte lgorithms Prtil info: Eh node is wre of its neighours nd of its link ost Rehility info exhnged mong djent nodes istne vetor lgorithm OMPUTER NETWORK ESIGN Review of network lyer protools - 9 OMPUTER NETWORK ESIGN Review of network lyer protools - Need for hierrhil routing Idel se ll routers identil Flt, non hierrhil network Unprtil Slility: with million destintions ll in one routing tle? Info exhnge to uild routing tles would require huge mount of ndwidth dministrtive utonomy Internet is network of networks (mnged independently) Eh network dministrtor is willing to devise its own routing poliies OMPUTER NETWORK ESIGN Review of network lyer protools - Hierrhil routing Router ggregted in res, nmed utonomous System (S) Set of routers, possily of omplex struture (mny sunets nd routers) under the sme dministrtive ontrol Protools run in S re nmed IGP: Interior Gtewy Protool Router in the sme S use the sme IGP routing protool Router in different S my use different IGP protools OMPUTER NETWORK ESIGN Review of network lyer protools - Hierrhil routing In every S gtewy routers re identified Responsile to route towrds destintions externl to the S Protools run mong S re nmed IGP protools Run IGP protools with other routers in the sme S Run inter-s (EGP: Exterior Gtewy Protool) with other gtewy router ddress ggregtion eomes key issue Routing tles reted y oth EGP nd IGP protools Routing Intr-S nd Inter-S. d. inter-s, intr-s routing in gtewy.. B. B Gtewys: Run inter-s protools mong tem Run intr-s protools with other routers within the sme S network lyer link lyer physil lyer OMPUTER NETWORK ESIGN Review of network lyer protools - 3 OMPUTER NETWORK ESIGN Review of network lyer protools - 4 Pg. 4

5 OMPUTER NETWORK ESIGN Network lyer protools Routing Intr-S nd Inter-S Host h.. d Intr-S routing Within S Inter-S routing Between S e B B.. B Intr-S routing In S B Host h Routing protools Internl Link ost often set equl to to route on the sis of hop ount RIP (distne vetor) RF 73 OSPF (link stte) RF 583 IS-IS (link stte) RF 4 Externl Poliy sed routing EGP (Exterior Gtewy Protool) RF 94 BGP (Border Gtewy Protool) RF 67 OMPUTER NETWORK ESIGN Review of network lyer protools - 5 OMPUTER NETWORK ESIGN Review of network lyer protools - 6 Pg. 5

Detection of Denial of Service attacks using AGURI

Detection of Denial of Service attacks using AGURI Detetion of Denil of Servie ttks using AGURI Ryo Kizki Keio Univ. kizki@sf.wide.d.jp Kenjiro Cho SonyCSL kj@sl.sony.o.jp Osmu Nkmur Keio Univ. osmu@wide.d.jp Astrt Denil of Servie ttks is divided into