Ad-Ho c On-Demand Distance V ector Routing Charles E. P erkins Adv anced Net w ork Dev elopmen t Sun Microsystems Menlo P ark, CA cp erkins@eng.sun.com Elizab eth Ro y er Dept of Electrical & Computer Engineering Univ ersit y of California San ta Barbara, Univ ersit y of California ero y er@alpha.ece.uscb.edu P erkins, Ro y er 1 Sun, UCSB
What an ad-ho c routing proto col needs Multi-hop paths � Self-starting � Dynamic top ology main tenance � Lo op-free � Lo w consumption of memory , bandwidth � Scalable to large no de p opulations � Lo calized e�ect of link break age � Minimal o v erhead for data transmission � Rapid con v ergence � and ... Multicast � P erkins, Ro y er 2 Sun, UCSB
A OD V: Ad-Ho c On-Demand Distance V ector Routing Quic k lo op-free con v ergence � Route creation , lo calizing the e�ect of top ology c hanges, and mini- on demand � mizing con trol tra�c. Distance V ector, using Destination Sequence n um b ers for route up dates (on b oth � forw ard and rev erse paths) T riggered up dates and minimal latency for route replies � Reduced bandwidth utilization � t w o-dim'l metric: < seq#, hop-coun t > � Enables future aggregation computations � P erkins, Ro y er 3 Sun, UCSB
A OD V Unicast Route Disco v ery RREQ ( r oute r e que st ) is broadcast Rev erse path is set up along the w a y � RREQ message con tains < bcast id; dest ip; dest seq no; � sr c ip; sr c seq no; hop count > RREP ( r eply ) is unicast bac k oute r F rom destination if necessary � F rom in termediate no de if that no de has a recen t route � P erkins, Ro y er 4 Sun, UCSB
Route Request (RREQ) Message F ormat 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type Reserved Hop Count Broadcast ID Destination IP address Destination Sequence Number Source IP Address Source Sequence Number Source sequence n um b er helps set up rev erse route short-live d Destination sequence # is the for the requested destination (or, zero) last known Hop Coun t incremen ted b y ev ery in termediate no de P erkins, Ro y er 5 Sun, UCSB
Route Reply (RREP) Message F ormat 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type L Reserved Hop Count Destination IP address Destination Sequence Number Lifetime Lifetime con trols ho w long the remains v alid at an in termediate no de after it is no longer active Hop Coun t incremen ted b y ev ery in termediate no de If broadcast with TTL=1, serv es as a message hel lo P erkins, Ro y er 6 Sun, UCSB
Link Break age No des remem b er activ e routes � Next hop breaks neigh b ors using that route are noti�ed � ! Noti�cation is a RREP with: � metric = 1 { dest seqno = previous + 1 { and is sen t to eac h activ e neigh b or P erkins, Ro y er 7 Sun, UCSB
A OD V Multicast Route Disco v ery Message t yp es: RREQ, with new �ags `J' ( Join ) and `R' ( R ep air ) � RREP � MINV � Multicast routes ha v e a destination sequence n um b er and m ultiple next hops Multicast Group Leader extension for RREQ, RREP � P erkins, Ro y er 8 Sun, UCSB
Multicast In v alidate Message F ormat 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 Type Reserved Hop Count Destination IP address Destination Sequence Number Source IP Address Source Sequence Number A prosp ectiv e m ulticast group mem b er only needs one link to the m ulticast distri- bution tree, but it ma y receiv e m ultiple RREP messages. The MINV message prunes all the extra branc hes from the m ulticast tree. In terme- diate no des that are not part of the m ulticast group, that receiv e MINV on their only outgoing link, prune themselv es from the tree. P erkins, Ro y er 9 Sun, UCSB
T ree Main tenance Multicast group leader main tains group sequence n um b er � Pruning (if no de lea v es tree) � leaf no des send MINV { in termediate no des remain { Multicast group leader broadcasts GR OUP HELLO p erio dically , con taining the m ul- ticast group address, sequence n um b er, and group leader's address. P erkins, Ro y er 10 Sun, UCSB
Link Break age No des remem b er m ulticast tree branc hes No de further from m ulticast group leader initiates link repair Only no des whic h are closer to group leader can send RREP No de initiating repair selects new branc h, sends MINV No resp onse after RREQ RETRIES means tree is partitioned Initiating no de b ecomes new group leader, issues Group Hello P erkins, Ro y er 11 Sun, UCSB
Merging Disconnected T rees If a no de hears Group Hello from t w o group leaders, it can repair the m ulticast tree Sends RREQ with `R' ( r ep air ) �ag set to group leader of its partition � Only group leader can resp ond to RREQ with R �ag set � Group leader sends RREQ with `J' ( Join ) �ag set to other group leader � Other group leader sends RREP to no de � Group Leader with smaller IP address b ecomes new group leader � New Group Leader broadcasts Group Hello with new group leader information � P erkins, Ro y er 12 Sun, UCSB
Ad-ho c Net w orking Example MH MH MH MH 3 4 MH MH 5 MH MH MH MH 8 2 MH MH 6 MH MH MH MH 7 1 MH MH 1 Supp ose mo v es a w a y from to w ards , and has activ e sessions with M H M H M H 1 2 7 and . The follo wing actions o ccur: M H M H 3 6 notices that its link to is brok en M H M H � 2 1 M H c hec ks its routing table, and �nds that its link to M H w as activ ely in � 2 1 use b y and . M H M H 3 4 P erkins, Ro y er 13 Sun, UCSB
unicasts an 1 -metric route up date, with an incremen ted destination se- M H � 2 quence n um b er, to and . ma y subsequen tly issue a new route M H M H M H 3 4 3 request for . M H 1 also notes that its route to w as activ ely in use, and forw ards the M H M H � 4 1 1 -metric route up date to . M H 6 The 1 -metric route up date for M H ma y also b e included in the next hel lo � 1 message issued b y M H 2 ma y subsequen tly issue a new route request for M H M H � 6 1 An y subsequen t route request for whic h is satis�ed b y a route reply through M H � 1 ma y cause to up date its route table M H M H 2 2 Destination sequencing main tains nice prop erties of lo op-freeness, and eliminates Bellman-F ord "coun ting to in�nit y" problem. P erkins, Ro y er 14 Sun, UCSB
Repairing Multicast T ree Breaks 7 4 3 9 6 2 8 1 Group 10 Leader 5 No de 4 detects link break age, initiates group repair Only no des in subtree con taining group leader can issue RREP After RREQ RETRIES, no de 4 broadcasts GR OUP HELLO message as a new leader P erkins, Ro y er 15 Sun, UCSB
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