Rou$ng. Rou$ng: Mapping Link to Path. Data and Control Planes. Rou$ng vs. Forwarding. Rou$ng Protocols. What Does the Protocol Compute?

Transcription

1 Ro$ng: Mapping Link o Pah Ro$ng Jennifer Reford COS : Comper Nework Lecre: MW 0-0:0am in Archiecre N0 hgp:// link eion pah name addre Daa and Conrol Plane daa plane Proceor Swiching Fabric conrol plane Ro$ng. Forwarding Ro$ng: conrol plane Comp$ng pah he packe will follow Roer alking among hemele Crea$ng he forwarding able Forwarding: daa plane Direc$ng a daa packe o an ogoing link Uing he forwarding able Ro$ng Proocol Wha doe he proocol compe? E.g., hore pah Wha algorihm doe he proocol rn? E.g., link- ae ro$ng How do roer learn end- ho loca$on? E.g., injec$ng ino he ro$ng proocol Wha Doe he Proocol Compe?

2 Differen Wa o Repreen Pah Sa$c model Wha i comped, i.e., wha i he ocome No how he compa$on i performed Trade- off Sae o repreen he pah Efficienc of he pah Abili o ppor ml$ple pah Complei of pah compa$on Spanning Tree One ree ha reache eer node Single pah beween each pair of node No loop, o can ppor broadca eail B, pah are long, and ome link no ed 7 8 Shore Pah Shore pah() beween pair of node A hore- pah ree rooed a each node Min hop con or min m of edge weigh Ml$pah ro$ng i limied o Eqal Co Ml$Pah Locall Polic a Each Hop Locall be pah Local polic: each node pick he pah i like be among he pah choen b i neighbor d d d d d d d d d d d d d d d d d d d d d d End- o- End Pah Selec$on End- o- end pah elec$on Each node pick i own end o end pah independen of wha oher pah oher node e More ae and complei in he node How o Compe Pah?

3 Spanning Tree Algorihm Elec a roo The wich wih he malle iden$fier And form a ree from here Algorihm Repeaedl alk o neighbor I hink node Y i he roo M diance from Y i d Updae baed on neighbor Smaller id a he roo Smaller diance d+ One hop roo Three hop Ued in Eherne LAN Spanning Tree Eample: Swich # Swich # hink i i he roo Send (, 0, ) meage o and 7 Swich # hear from # Receie (, 0, ) meage from and hink ha # i he roo And realie i i j one hop awa Swich # hear from #7 Receie (,, 7) from 7 B, hi i a longer pah, o prefer - oer - 7- And remoe - 7 link from he ree 7 Shore- Pah Problem Compe: pah co o all node From a gien orce o all oher node Co of he pah hrogh each ogoing link Ne hop along he lea- co pah o Link Sae: Dijkra Algorihm Flood he opolog informa$on o all node Each node compe hore pah o oher node Iniialiaion S = {} for all node if ( i adjacen o ) D() = c(,) ele D() = Loop add w wih malle D(w) o S pdae D() for all adjacen : D() = min{d(), D(w) + c(w,)} n-l all node are in S Ued in OSPF and IS-IS Link- Sae Ro$ng Eample Link- Sae Ro$ng Eample (con.) 7 8

4 Link Sae: Shore- Pah Tree Shore- pah ree from Forwarding able a link (,) w (,w) (,w) w (,) (,) (,w) (,w) Diance Vecor: Bellman- Ford Algo Define diance a each node d () = co of lea- co pah from o Updae diance baed on neighbor d () = min {c(,) + d ()} oer all neighbor w d () = min{c(,) + d (), c(,w) + d w ()} Ued in RIP and EIGRP 9 0 Diance Vecor Eample Diance Vecor Eample (Con.) w d ()= d ()= w d ()= min{+d (), +d ()} = w d w ()= min{+d (), +d (), +d ()} = w d ()= min{+d (), +d w ()} = Pah- Vecor Ro$ng Eenion of diance- ecor ro$ng Sppor fleible ro$ng policie Ke idea: ader$e he en$re pah Diance ecor: end diance meric per de d Pah ecor: end he en-re pah for each de d Pah- Vecor: Fleible Policie Each node can appl local policie Pah elec$on: Which pah o e? Pah epor: Which pah o ader$e? Node prefer,, oer, Node doen le hear he pah, d: pah (,) d: pah () daa raffic Ued in BGP daa raffic d

5 End- o- End Signaling Eablih end- o- end pah in adance Learn he opolog (a in link- ae ro$ng) End ho or roer compe and ignal a pah Signaling: inall enr for each circi a each hop Forwarding: look p he circi id in he able : 7 : 7 link 7 : : 8 Ued in MPLS wih RSVP link link 8 Sorce Ro$ng Similar o end- o- end ignaling B he daa packe carrie he hop in he pah End- ho conrol Tell he end ho he opolog Le he end ho elec he end- o- end pah Varia$on of orce ro$ng Sric: pecif eer hop Looe: pecif inermediae poin Ued in IP orce roing (b almo alwa diabled) 7 Learning Where he Ho Are Finding he Ho Bilding a forwarding able Comp$ng pah beween nework elemen and figring o where he end- ho are How o find he ho? Learning/flooding Injec$ng ino he ro$ng proocol Diemina$on ing a differen proocol Direcor erice 8 Learning and Flooding When a frame arrie Inpec he orce addre Aociae addre wih he incoming inerface A Swich learn how o reach A. 9 B D C When he frame ha an nfamiliar de-na-on Forward o all inerface ecep incoming inerface A When in dob, ho! Ued in Eherne LAN B D C Injec ino Ro$ng Proocol Trea he end ho (or bne) a a node And dieminae in he ro$ng proocol E.g., flood informa$on abo where addree agach 0... Ued in OSPF and IS-IS, epeciall in enerprie nework

6 Dieminae Wih Anoher Proocol Diribe ing anoher proocol One roer learn he roe and hare he informa$on wih oher roer learn a roe o d (e.g., ia BGP) dieminae roe o oher roer Direcor Serice Conac a erice o learn he loca$on Look p he end- ho or bne addre o deermine he label o p on he packe direcor Ho d i a egre e e Inernal BGP (ibgp) ed in backbone nework Ued in ome daa cener. i Encaplae packe o end o egre e. d Conclion: Man Differen Sol$on Eherne LAN and home nework Spanning ree, MAC learning, flooding Enerprie Link- ae ro$ng, injec$ng bne addree Backbone Link- ae ro$ng inide, pah- ecor ro$ng wih neighboring domain, and ibgp diemina$on Daa cener Man differen ol$on, $ll in fl Frida precep Ho configra$on Coming Ne Monda lecre Ge lecre on conge$on conrol Profeor Michael Freedman Wedneda lecre Qali of erice