CS Networks and Distributed Systems. Lecture 8: Inter Domain Routing

Save this PDF as:
 WORD  PNG  TXT  JPG

Size: px
Start display at page:

Download "CS Networks and Distributed Systems. Lecture 8: Inter Domain Routing"

Transcription

1 CS 3700 Networks and Distributed Systems Lecture 8: Inter Domain Routing Revised 2/4/2014

2 Network Layer, Control Plane 2 Data Plane Application Presentation Session Transport Network Data Link Physical Function:! Set up routes between networks Key challenges:! Implementing provider policies! Creating stable paths RIP OSPF BGP Control Plane

3 3 Outline BGP Basics Stable Paths Problem BGP in the Real World

4 ASs, Revisited 4 AS-1 AS-3 Interior Routers AS-2 BGP Routers

5 AS Numbers 5 Each AS identified by an ASN number! 16-bit values (latest protocol supports 32-bit ones)! are reserved Currently, there are > ASNs! AT&T: 5074, 6341, 7018,! Sprint: 1239, 1240, 6211, 6242,! Northeastern: 156! North America ASs! ftp://ftp.arin.net/info/asn.txt

6 Inter-Domain Routing 6 Global connectivity is at stake!! Thus, all ASs must use the same protocol! Contrast with intra-domain routing

7 Inter-Domain Routing 6 Global connectivity is at stake!! Thus, all ASs must use the same protocol! Contrast with intra-domain routing What are the requirements?! Scalability! Flexibility in choosing routes Cost Routing around failures

8 Inter-Domain Routing 6 Global connectivity is at stake!! Thus, all ASs must use the same protocol! Contrast with intra-domain routing What are the requirements?! Scalability! Flexibility in choosing routes Cost Routing around failures Question: link state or distance vector?

9 Inter-Domain Routing 6 Global connectivity is at stake!! Thus, all ASs must use the same protocol! Contrast with intra-domain routing What are the requirements?! Scalability! Flexibility in choosing routes Cost Routing around failures Question: link state or distance vector?! Trick question: BGP is a path vector protocol

10 BGP 7 Border Gateway Protocol! De facto inter-domain protocol of the Internet! Policy based routing protocol! Uses a Bellman-Ford path vector protocol

11 BGP 7 Border Gateway Protocol! De facto inter-domain protocol of the Internet! Policy based routing protocol! Uses a Bellman-Ford path vector protocol Relatively simple protocol, but! Complex, manual configuration

12 BGP 7 Border Gateway Protocol! De facto inter-domain protocol of the Internet! Policy based routing protocol! Uses a Bellman-Ford path vector protocol Relatively simple protocol, but! Complex, manual configuration! Entire world sees advertisements Errors can screw up traffic globally

13 BGP 7 Border Gateway Protocol! De facto inter-domain protocol of the Internet! Policy based routing protocol! Uses a Bellman-Ford path vector protocol Relatively simple protocol, but! Complex, manual configuration! Entire world sees advertisements Errors can screw up traffic globally! Policies driven by economics How much $$$ does it cost to route along a given path? Not by performance (e.g. shortest paths)

14 BGP Relationships 8

15 BGP Relationships 8 Provider Customer pays provider Customer

16 BGP Relationships 8 Provider Customer pays provider Customer

17 BGP Relationships 8

18 BGP Relationships 8 Peers do not pay each other Peer 1 Peer 2 Peer 3

19 BGP Relationships 8 Peer 1 Peer 2 Peer 3

20 BGP Relationships 8 Peer 1 Peer 2 Peer 3

21 BGP Relationships 8 Peer 2 has no incentive to route 1! 3 Peer 1 Peer 2 Peer 3

22 BGP Relationships 8 Provider Customer Customer

23 BGP Relationships 8 Provider Customer Customer

24 Tier-1 ISP Peering 9 Inteliquent Centurylink AT&T Verizon Business Level 3 Sprint XO Communications

25

26 Peering Wars 11 Peer Reduce upstream costs Improve end-to-end performance May be the only way to connect to parts of the Internet Don t Peer You would rather have customers Peers are often competitors Peering agreements require periodic renegotiation

27 Peering Wars 11 Peer Reduce upstream costs Improve end-to-end performance May be the only way to connect to parts of the Internet Don t Peer You would rather have customers Peers are often competitors Peering agreements require periodic renegotiation Peering struggles in the ISP world are extremely contentions, agreements are usually confidential

28 Two Types of BGP Neighbors 12

29 Two Types of BGP Neighbors 12 IGP Exterior routers also speak IGP

30 Two Types of BGP Neighbors 12 ebgp ebgp

31 Two Types of BGP Neighbors 12 ebgp ibgp ibgp ebgp

32 Full ibgp Meshes 13

33 Full ibgp Meshes 13 ibgp ebgp

34 Full ibgp Meshes 13 ibgp ebgp Question: why do we need ibgp?! OSPF does not include BGP policy info! Prevents routing loops within the AS

35 Full ibgp Meshes 13 ibgp ebgp Question: why do we need ibgp?! OSPF does not include BGP policy info! Prevents routing loops within the AS ibgp updates do not trigger announcements

36 Path Vector Protocol 14 AS-path: sequence of ASs a route traverses! Like distance vector, plus additional information Used for loop detection and to apply policy Default choice: route with fewest # of ASs AS /16 AS 2 AS /16 AS /16 AS /16: AS 2! AS 3! AS /16: AS 2! AS /16: AS 2! AS 5

37 BGP Operations (Simplified) 15 Establish session on TCP port 179 AS-1 Exchange active routes Exchange incremental updates BGP Session AS-2

38 Four Types of BGP Messages 16 Open: Establish a peering session. Keep Alive: Handshake at regular intervals. Notification: Shuts down a peering session. Update: Announce new routes or withdraw previously announced routes.

39 Four Types of BGP Messages 16 Open: Establish a peering session. Keep Alive: Handshake at regular intervals. Notification: Shuts down a peering session. Update: Announce new routes or withdraw previously announced routes. announcement = IP prefix + attributes values

40 BGP Attributes 17 Attributes used to select best path! LocalPref Local preference policy to choose most preferred route Overrides default fewest AS behavior

41 BGP Attributes 17 Attributes used to select best path! LocalPref Local preference policy to choose most preferred route Overrides default fewest AS behavior! Multi-exit Discriminator (MED) Specifies path for external traffic destined for an internal network Chooses peering point for your network

42 BGP Attributes 17 Attributes used to select best path! LocalPref Local preference policy to choose most preferred route Overrides default fewest AS behavior! Multi-exit Discriminator (MED) Specifies path for external traffic destined for an internal network Chooses peering point for your network! Import Rules What route advertisements do I accept?! Export Rules Which routes do I forward to whom?

43 Route Selection Summary 18 18

44 Route Selection Summary Highest Local Preference Enforce relationships

45 Route Selection Summary Highest Local Preference Enforce relationships Shortest AS Path Lowest MED Lowest IGP Cost to BGP Egress Traffic engineering

46 Route Selection Summary Highest Local Preference Enforce relationships Shortest AS Path Lowest MED Lowest IGP Cost to BGP Egress Lowest Router ID Traffic engineering When all else fails, break ties

47 Shortest AS Path!= Shortest Path 19 Source Destination

48 Shortest AS Path!= Shortest Path 19 Source?? Destination

49 Shortest AS Path!= Shortest Path 19 4 hops 4 ASs? Source? Destination

50 Shortest AS Path!= Shortest Path 19 4 hops 4 ASs? Source? 9 hops 2 ASs Destination

51 Shortest AS Path!= Shortest Path 19 4 hops 4 ASs? Source? 9 hops 2 ASs Destination

52 Hot Potato Routing 20 Source Destination

53 Hot Potato Routing 20 Source?? Destination

54 Hot Potato Routing 20? Source? 3 hops total, 3 hops cost Destination

55 Hot Potato Routing 20 5 hops total, 2 hops cost? Source? 3 hops total, 3 hops cost Destination

56 Hot Potato Routing 20 5 hops total, 2 hops cost? Source? 3 hops total, 3 hops cost Destination

57 Importing Routes 21

58 Importing Routes 21 ISP Routes

59 Importing Routes 21 ISP Routes From Customer

60 Importing Routes 21 ISP Routes From Peer From Peer From Customer

61 Importing Routes 21 From Provider ISP Routes From Peer From Peer From Customer

62 Exporting Routes 22

63 Exporting Routes 22 To Customer Customers get all routes

64 Exporting Routes 22 Customer and ISP routes only To Peer To Peer To Customer Customers get all routes

65 Exporting Routes 22 To Provider Customer and ISP routes only To Peer To Peer To Customer Customers get all routes

66 Exporting Routes 22 $$$ generating routes To Provider Customer and ISP routes only To Peer To Peer To Customer Customers get all routes

67 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used)

68 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used) C-P P-P

69 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used) C-P P-P

70 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used) C-P P-P P-P P-C

71 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used) C-P P-P P-P P-C

72 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used) P-P P-P C-P P-C P-C P-P

73 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used) P-P P-P C-P P-C P-C P-P

74 Modeling BGP 23 AS relationships! Customer/provider! Peer! Sibling, IXP Gao-Rexford model! AS prefers to use customer path, then peer, then provider Follow the money!! Valley-free routing! Hierarchical view of routing (incorrect but frequently used) P-P P-P C-P P-C P-C P-P

75 AS Relationships: It s Complicated 24 GR Model is strictly hierarchical! Each AS pair has exactly one relationship! Each relationship is the same for all prefixes

76 AS Relationships: It s Complicated 24 GR Model is strictly hierarchical! Each AS pair has exactly one relationship! Each relationship is the same for all prefixes In practice it s much more complicated! Rise of widespread peering! Regional, per-prefix peerings! Tier-1 s being shoved out by hypergiants! IXPs dominating traffic volume

77 AS Relationships: It s Complicated 24 GR Model is strictly hierarchical! Each AS pair has exactly one relationship! Each relationship is the same for all prefixes In practice it s much more complicated! Rise of widespread peering! Regional, per-prefix peerings! Tier-1 s being shoved out by hypergiants! IXPs dominating traffic volume Modeling is very hard, very prone to error! Huge potential impact for understanding Internet behavior

78 Other BGP Attributes 25 AS_SET! Instead of a single AS appearing at a slot, it s a set of Ases! Why?

79 Other BGP Attributes 25 AS_SET! Instead of a single AS appearing at a slot, it s a set of Ases! Why? Communities! Arbitrary number that is used by neighbors for routing decisions Export this route only in Europe Do not export to your peers! Usually stripped after first interdomain hop! Why?

80 Other BGP Attributes 25 AS_SET! Instead of a single AS appearing at a slot, it s a set of Ases! Why? Communities! Arbitrary number that is used by neighbors for routing decisions Export this route only in Europe Do not export to your peers! Usually stripped after first interdomain hop! Why? Prepending! Lengthening the route by adding multiple instances of ASN! Why?

81 26 Outline BGP Basics Stable Paths Problem BGP in the Real World

82 What Problem is BGP Solving? Underlying Problem Distributed Solution Shortest Paths RIP, OSPF, IS-IS, etc.??? BGP

83 What Problem is BGP Solving? Underlying Problem Distributed Solution Shortest Paths RIP, OSPF, IS-IS, etc.??? BGP Knowing??? can:! Aid in the analysis of BGP policy! Aid in the design of BGP extensions! Help explain BGP routing anomalies! Give us a deeper understanding of the protocol

84 The Stable Paths Problem 28 An instance of the SPP:! Graph of nodes and edges! Node 0, called the origin

85 The Stable Paths Problem 28 An instance of the SPP:! Graph of nodes and edges! Node 0, called the origin! A set of permitted paths from each node to the origin Each set contains the null path

86 The Stable Paths Problem 28 An instance of the SPP:! Graph of nodes and edges! Node 0, called the origin! A set of permitted paths from each node to the origin Each set contains the null path! Each set of paths is ranked Null path is always least preferred

87 A Solution to the SPP 29 A solution is an assignment of permitted paths to each node such that:! Node u s path is either null or uwp, where path uw is assigned to node w and edge u! w exists! Each node is assigned the higest ranked path that is consistent with their neighbors

88 A Solution to the SPP 29 A solution is an assignment of permitted paths to each node such that:! Node u s path is either null or uwp, where path uw is assigned to node w and edge u! w exists! Each node is assigned the higest ranked path that is consistent with their neighbors

89 A Solution to the SPP 29 A solution is an assignment of permitted paths to each node such that:! Node u s path is either null or uwp, where path uw is assigned to node w and edge u! w exists! Each node is assigned the higest ranked path that is consistent with their neighbors

90 A Solution to the SPP 29 A solution is an assignment of permitted paths to each node such that:! Node u s path is either null or uwp, where path uw is assigned to node w and edge u! w exists! Each node is assigned the higest ranked path that is consistent with their neighbors

91 A Solution to the SPP 29 A solution is an assignment of permitted paths to each node such that:! Node u s path is either null or uwp, where path uw is assigned to node w and edge u! w exists! Each node is assigned the higest ranked path that is consistent with their neighbors

92 A Solution to the SPP 29 A solution is an assignment of permitted paths to each node such that:! Solutions Node u s path need is either not use null or uwp, where path uw is assigned to the node shortest w and edge paths, u! or w exists form! Each node a spanning is assigned tree the higest ranked path that is consistent with their neighbors

93 Simple SPP Example

94 Simple SPP Example

95 Simple SPP Example

96 Simple SPP Example

97 Simple SPP Example

98 Simple SPP Example

99 Simple SPP Example Each node gets its preferred route 0 Totally stable topology

100 Good Gadget

101 Good Gadget

102 Good Gadget

103 Good Gadget

104 Good Gadget

105 Good Gadget Not every node gets preferred route Topology is still stable Only one stable configuration 0 No matter which router chooses first!

106 SPP May Have Multiple Solutions

107 SPP May Have Multiple Solutions

108 SPP May Have Multiple Solutions

109 SPP May Have Multiple Solutions

110 SPP May Have Multiple Solutions

111 SPP May Have Multiple Solutions

112 SPP May Have Multiple Solutions

113 Bad Gadget

114 Bad Gadget

115 Bad Gadget

116 Bad Gadget

117 Bad Gadget

118 Bad Gadget

119 Bad Gadget

120 Bad Gadget

121 Bad Gadget

122 Bad Gadget

123 Bad Gadget

124 Bad Gadget

125 Bad Gadget

126 Bad Gadget That was only one round of oscillation! This keeps going, infinitely Problem stems from: Local (not global) decisions Ability of one node to improve its path selection

127 SPP Explains BGP Divergence 34 BGP is not guaranteed to converge to stable routing! Policy inconsistencies may lead to livelock! Protocol oscillation Solvable Can Diverge Must Converge Must Diverge

128 SPP Explains BGP Divergence 34 BGP is not guaranteed to converge to stable routing! Policy inconsistencies may lead to livelock! Protocol oscillation Good Gadgets Solvable Can Diverge Bad Gadgets Must Converge Must Diverge Naughty Gadgets

129 Beware of Backup Policies

130 Beware of Backup Policies

131 Beware of Backup Policies BGP is not robust 0 It may not recover from link failure

132 BGP is Precarious

133 BGP is Precarious If node 1 uses path 1! 0, this is solvable

134 BGP is Precarious No longer stable

135 Can BGP Be Fixed? 37 Unfortunately, SPP is NP-complete

136 Can BGP Be Fixed? 37 Unfortunately, SPP is NP-complete Possible Solutions Dynamic Approach Extend BGP to detect and suppress policy-based oscillations?

137 Can BGP Be Fixed? 37 Unfortunately, SPP is NP-complete Possible Solutions Static Approach Dynamic Approach Automated Analysis of Routing Policies (This is very hard) Inter-AS coordination Extend BGP to detect and suppress policy-based oscillations?

138 Can BGP Be Fixed? 37 Unfortunately, SPP is NP-complete Possible Solutions Static Approach Dynamic Approach Automated Analysis of Routing Policies (This is very hard) Inter-AS coordination Extend BGP to detect and suppress policy-based oscillations? These approaches are complementary

139 38 Outline BGP Basics Stable Paths Problem BGP in the Real World

140 Motivation 39 Routing reliability/fault-tolerance on small time scales (minutes) not previously a priority Transaction oriented and interactive applications (e.g. Internet Telephony) will require higher levels of end-toend network reliability How well does the Internet routing infrastructure tolerate faults?

141 Conventional Wisdom 40 Internet routing is robust under faults! Supports path re-routing! Path restoration on the order of seconds BGP has good convergence properties! Does not exhibit looping/bouncing problems of RIP Internet fail-over will improve with faster routers and faster links More redundant connections (multi-homing) will always improve fault-tolerance

142 Delayed Routing Convergence 41 Conventional wisdom about routing convergence is not accurate! Measurement of BGP convergence in the Internet! Analysis/intuition behind delayed BGP routing convergence! Modifications to BGP implementations which would improve convergence times

143 Open Question 42 After a fault in a path to multi-homed site, how long does it take for majority of Internet routers to fail-over to secondary path? Customer Primary ISP Backup ISP

144 Open Question 42 After a fault in a path to multi-homed site, how long does it take for majority of Internet routers to fail-over to secondary path? Route Withdrawn Routing table convergence Primary ISP Customer Backup ISP

145 Open Question 42 After a fault in a path to multi-homed site, how long does it take for majority of Internet routers to fail-over to secondary path? Customer Primary ISP Route Withdrawn Routing table convergence Stable end-to-end paths Backup ISP Traffic

146 Bad News 43 With unconstrained policies:! Divergence! Possible create unsatisfiable policies! NP-complete to identify these policies! Happening today?

147 Bad News 43 With unconstrained policies:! Divergence! Possible create unsatisfiable policies! NP-complete to identify these policies! Happening today? With constrained policies (e.g. shortest path first)! Transient oscillations! BGP usually converges! It may take a very long time

148 Bad News 43 With unconstrained policies:! Divergence! Possible create unsatisfiable policies! NP-complete to identify these policies! Happening today? With constrained policies (e.g. shortest path first)! Transient oscillations! BGP usually converges! It may take a very long time BGP Beacons: focuses on constrained policies

149 16 Month Study of Convergence 44 Instrument the Internet! Inject BGP faults (announcements/withdrawals) of varied prefix and AS path length into topologically and geographically diverse ISP peering sessions! Monitor impact faults through Recording BGP peering sessions with 20 tier1/tier2 ISPs Active ICMP measurements (512 byte/second to 100 random web sites)! Wait two years (and 250,000 faults)

150 Measurement Architecture 45

151 Measurement Architecture 45 Researchers pretending to be an AS Researchers pretending to be an AS

152 Measurement Architecture 45

153 Measurement Architecture 45

154 Announcement Scenarios 46 Tup a new route is advertised Tdown A route is withdrawn! i.e. single-homed failure Tshort Advertise a shorter/better AS path! i.e. primary path repaired Tlong Advertise a longer/worse AS path! i.e. primary path fails

155 Major Convergence Results 47 Routing convergence requires an order of magnitude longer than expected! 10s of minutes Routes converge more quickly following Tup/Repair than Tdown/Failure events! Bad news travels more slowly Withdrawals (Tdown) generate several more announcements than new routes (Tup)

156 Example 48 BGP log of updates from AS2117 for route via AS2129 One withdrawal triggers 6 announcements and one withdrawal from 2117 Increasing AS path length until final withdrawal

157 Why So Many Announcements? 49 Events from AS 2177 AS 2041 AS 3508 AS 1 AS 5696 AS 2129 AS 2117

158 Why So Many Announcements? 49 Events from AS 2177 AS 2041 AS 3508 AS 1 AS 5696 AS 2129 AS 2117

159 Why So Many Announcements? 49 Events from AS Route Fails: AS 2129 AS 2041 AS 3508 AS 1 AS 5696 AS 2129 AS 2117

160 Why So Many Announcements? 49 Events from AS Route Fails: AS Announce: AS 2041 AS 3508 AS 1 AS 5696 AS 2129 AS 2117

161 Why So Many Announcements? 49 Events from AS Route Fails: AS Announce: Announce: AS 2041 AS 3508 AS 1 AS 5696 AS 2129 AS 2117

162 Why So Many Announcements? 49 Events from AS Route Fails: AS Announce: Announce: Announce: AS 2041 AS 3508 AS 1 AS 5696 AS 2129 AS 2117

163 Why So Many Announcements? 49 Events from AS Route Fails: AS Announce: Announce: Announce: Announce: Route Withdrawn: 2129 AS 2041 AS 3508 AS 1 AS 5696 AS 2129 AS 2117

164 How Many Announcements Does it Take For an AS to Withdraw a Route? 50

165 How Many Announcements Does it Take For an AS to Withdraw a Route? 50 Answer: up to 19

166 BGP Routing Table Convergence Times 100 Cumulative Percentage of Events New Route Long->Short Fail-over Short->Long Fail-Over Failure Tup Tshort Tlong Tdown Seconds Until Convergence Less than half of Tdown events converge within two minutes Tup/Tshort and Tdown/Tlong form equivalence classes Long tailed distribution (up to 15 minutes)

167 Failures, Fail-overs and Repairs 52 Bad news does not travel fast Repairs (Tup) exhibit similar convergence as long-short AS path fail-over Failures (Tdown) and short-long fail-overs (e.g. primary to secondary path) also similar! Slower than Tup (e.g. a repair)! 80% take longer than two minutes! Fail-over times degrade the greater the degree of multihoming

168 Intuition for Delayed Convergence 53 There exists possible ordering of messages such that BGP will explore ALL possible AS paths of ALL possible lengths BGP is O(N!), where N number of default-free BGP routers in a complete graph with default policy

169 Impact of Delayed Convergence 54 Why do we care about routing table convergence?! It impacts end-to-end connectivity for Internet paths ICMP experiment results! Loss of connectivity, packet loss, latency, and packet reordering for an average of 3-5 minutes after a fault Why?! Routers drop packets when next hop is unknown! Path switching spikes latency/delay! Multi-pathing causes reordering

170 In real life 55 Discussed worst case BGP behavior In practice, BGP policy prevents worst case from happening BGP timers also provide synchronization and limits possible orderings of messages

171 Inter-Domain Routing Summary 56 BGP4 is the only inter-domain routing protocol currently in use world-wide Issues?! Lack of security! Ease of misconfiguration! Poorly understood interaction between local policies! Poor convergence! Lack of appropriate information hiding! Non-determinism! Poor overload behavior

172 Lots of research into how to fix this 57 Security! BGPSEC, RPKI Misconfigurations, inflexible policy! SDN Policy Interactions! PoiRoot (root cause analysis) Convergence! Consensus Routing Inconsistent behavior! LIFEGUARD, among others

173 Why are these still issues? 58 Backward compatibility Buy-in / incentives for operators Stubbornness

174 Why are these still issues? 58 Backward compatibility Buy-in / incentives for operators Stubbornness Very similar issues to IPv6 deployment

Next Lecture: Interdomain Routing : Computer Networking. Outline. Routing Hierarchies BGP

Next Lecture: Interdomain Routing : Computer Networking. Outline. Routing Hierarchies BGP Next Lecture: Interdomain Routing BGP 15-744: Computer Networking L-3 BGP Assigned Reading MIT BGP Class Notes [Gao00] On Inferring Autonomous System Relationships in the Internet Ooops 2 Outline Need

More information

CS 268: Computer Networking. Next Lecture: Interdomain Routing

CS 268: Computer Networking. Next Lecture: Interdomain Routing CS 268: Computer Networking L-3 BGP Next Lecture: Interdomain Routing BGP Assigned Reading MIT BGP Class Notes [Gao00] On Inferring Autonomous System Relationships in the Internet 2 Outline Need for hierarchical

More information

CS 640: Introduction to Computer Networks. Intra-domain routing. Inter-domain Routing: Hierarchy. Aditya Akella

CS 640: Introduction to Computer Networks. Intra-domain routing. Inter-domain Routing: Hierarchy. Aditya Akella CS 640: Introduction to Computer Networks Aditya Akella Lecture 11 - Inter-Domain Routing - BGP (Border Gateway Protocol) Intra-domain routing The Story So Far Routing protocols generate the forwarding

More information

Interdomain Routing Reading: Sections P&D 4.3.{3,4}

Interdomain Routing Reading: Sections P&D 4.3.{3,4} Interdomain Routing Reading: Sections P&D 4.3.{3,4} EE122: Intro to Communication Networks Fall 2006 (MW 4:00-5:30 in Donner 155) Vern Paxson TAs: Dilip Antony Joseph and Sukun Kim http://inst.eecs.berkeley.edu/~ee122/

More information

COMP/ELEC 429 Introduction to Computer Networks

COMP/ELEC 429 Introduction to Computer Networks COMP/ELEC 429 Introduction to Computer Networks Lecture 11: Inter-domain routing Slides used with permissions from Edward W. Knightly, T. S. Eugene Ng, Ion Stoica, Hui Zhang T. S. Eugene Ng eugeneng at

More information

Lecture 17: Border Gateway Protocol

Lecture 17: Border Gateway Protocol Lecture 17: Border Gateway Protocol CSE 123: Computer Networks Alex C. Snoeren Some figures courtesy Mike Freedman Lecture 18 Overview Border Gateway Protocol (BGP) The canonical path vector protocol How

More information

Internet inter-as routing: BGP

Internet inter-as routing: BGP Internet inter-as routing: BGP BGP (Border Gateway Protocol): the de facto standard BGP provides each AS a means to: 1. Obtain subnet reachability information from neighboring ASs. 2. Propagate the reachability

More information

Dynamics of Hot-Potato Routing in IP Networks

Dynamics of Hot-Potato Routing in IP Networks Dynamics of Hot-Potato Routing in IP Networks Jennifer Rexford AT&T Labs Research http://www.research.att.com/~jrex Joint work with Renata Teixeira (UCSD), Aman Shaikh (AT&T), and Timothy Griffin (Intel)

More information

Inter-Domain Routing: BGP

Inter-Domain Routing: BGP Inter-Domain Routing: BGP Richard T. B. Ma School of Computing National University of Singapore CS 3103: Compute Networks and Protocols Inter-Domain Routing Internet is a network of networks Hierarchy

More information

Internet Routing Protocols Lecture 03 Inter-domain Routing

Internet Routing Protocols Lecture 03 Inter-domain Routing Internet Routing Protocols Lecture 03 Inter-domain Routing Advanced Systems Topics Lent Term, 2008 Timothy G. Griffin Computer Lab Cambridge UK Autonomous Routing Domains A collection of physical networks

More information

Lecture 16: Border Gateway Protocol

Lecture 16: Border Gateway Protocol Lecture 16: Border Gateway Protocol CSE 123: Computer Networks Alex C. Snoeren Some figures courtesy Mike Freedman Lecture 16 Overview Border Gateway Protocol (BGP) The canonical path vector protocol How

More information

BGP. Autonomous system (AS) BGP version 4

BGP. Autonomous system (AS) BGP version 4 BGP Border Gateway Protocol (an introduction) dr. C. P. J. Koymans Informatics Institute University of Amsterdam March 11, 2008 General ideas behind BGP Background Providers, Customers and Peers External

More information

How does a router know where to send a packet next?

How does a router know where to send a packet next? How does a router know where to send a packet next? The Problem Which path should packets take from A to B? A B R2 R R4 R3 C D 2 The Internet forwards packets hop-by-hop Data IP Address Next-hop A R B

More information

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System)

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System) BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 310, 2014/03/11 10:50:06) Monday, March 10, 2014 General ideas behind BGP Background Providers,

More information

This appendix contains supplementary Border Gateway Protocol (BGP) information and covers the following topics:

This appendix contains supplementary Border Gateway Protocol (BGP) information and covers the following topics: Appendix C BGP Supplement This appendix contains supplementary Border Gateway Protocol (BGP) information and covers the following topics: BGP Route Summarization Redistribution with IGPs Communities Route

More information

An overview of how packets are routed in the Internet

An overview of how packets are routed in the Internet An overview of how packets are routed in the Internet 1 Dijkstra s shortest path first algorithm (example of a Link State Algorithm ) 1. Exchange link state: A router floods to every other router the state

More information

Computer Networking Introduction

Computer Networking Introduction Computer Networking Introduction Halgurd S. Maghdid Software Engineering Department Koya University-Koya, Kurdistan-Iraq Lecture No.15 Chapter 4: outline 4.1 introduction 4.2 virtual circuit and datagram

More information

Last time. Transitioning to IPv6. Routing. Tunneling. Gateways. Graph abstraction. Link-state routing. Distance-vector routing. Dijkstra's Algorithm

Last time. Transitioning to IPv6. Routing. Tunneling. Gateways. Graph abstraction. Link-state routing. Distance-vector routing. Dijkstra's Algorithm Last time Transitioning to IPv6 Tunneling Gateways Routing Graph abstraction Link-state routing Dijkstra's Algorithm Distance-vector routing Bellman-Ford Equation 10-1 This time Distance vector link cost

More information

CS321: Computer Networks Unicast Routing

CS321: Computer Networks Unicast Routing CS321: Computer Networks Unicast Routing Dr. Manas Khatua Assistant Professor Dept. of CSE IIT Jodhpur E-mail: manaskhatua@iitj.ac.in Introduction The goal of the network layer is deliver a datagram from

More information

CS 204: BGP. Jiasi Chen Lectures: MWF 12:10-1pm Humanities and Social Sciences

CS 204: BGP. Jiasi Chen Lectures: MWF 12:10-1pm Humanities and Social Sciences CS 204: BGP Jiasi Chen Lectures: MWF 12:10-1pm Humanities and Social Sciences 1403 http://www.cs.ucr.edu/~jiasi/teaching/cs204_spring17/ 1 Overview AS relationships Inter-AS routing BGP Example Paper discussion

More information

BGP. Border Gateway Protocol (an introduction) Karst Koymans. Informatics Institute University of Amsterdam. (version 17.3, 2017/12/04 13:20:08)

BGP. Border Gateway Protocol (an introduction) Karst Koymans. Informatics Institute University of Amsterdam. (version 17.3, 2017/12/04 13:20:08) BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 17.3, 2017/12/04 13:20:08) Tuesday, December 5, 2017 Karst Koymans (UvA) BGP Tuesday,

More information

Routing(2) Inter-domain Routing

Routing(2) Inter-domain Routing Routing(2) Inter-domain Routing Information Network I Youki Kadobayashi 1 Outline! Distance vector routing! Link state routing! IGP and EGP Intra-domain routing protocol, inter-domain routing protocol!

More information

CS 43: Computer Networks Internet Routing. Kevin Webb Swarthmore College November 16, 2017

CS 43: Computer Networks Internet Routing. Kevin Webb Swarthmore College November 16, 2017 CS 43: Computer Networks Internet Routing Kevin Webb Swarthmore College November 16, 2017 1 Hierarchical routing Our routing study thus far - idealization all routers identical network flat not true in

More information

Inter-domain Routing. Outline. Border Gateway Protocol

Inter-domain Routing. Outline. Border Gateway Protocol Inter-domain Routing Outline Border Gateway Protocol Internet Structure Original idea CS 640 2 Internet Structure Today CS 640 3 Route Propagation in the Internet Autonomous System (AS) corresponds to

More information

Backbone Networks. Networking Case Studies. Backbone Networks. Backbone Topology. Mike Freedman COS 461: Computer Networks.

Backbone Networks. Networking Case Studies. Backbone Networks. Backbone Topology. Mike Freedman COS 461: Computer Networks. Networking Case Studies Datacenter Backbone Networks Enterprise Backbone Mike Freedman COS 6: Computer Networks Cellular h>p://www.cs.princeton.edu/courses/archive/spr/cos6/ Wireless Backbone Networks

More information

Module 6 Implementing BGP

Module 6 Implementing BGP Module 6 Implementing BGP Lesson 1 Explaining BGP Concepts and Terminology BGP Border Gateway Protocol Using BGP to Connect to the Internet If only one ISP, do not need BGP. If multiple ISPs, use BGP,

More information

Inter-Autonomous-System Routing: Border Gateway Protocol

Inter-Autonomous-System Routing: Border Gateway Protocol Inter-Autonomous-System Routing: Border Gateway Protocol Antonio Carzaniga Faculty of Informatics University of Lugano June 14, 2005 Outline Hierarchical routing BGP Routing Routing Goal: each router u

More information

CS 457 Networking and the Internet. The Global Internet (Then) The Global Internet (And Now) 10/4/16. Fall 2016

CS 457 Networking and the Internet. The Global Internet (Then) The Global Internet (And Now) 10/4/16. Fall 2016 CS 457 Networking and the Internet Fall 2016 The Global Internet (Then) The tree structure of the Internet in 1990 The Global Internet (And Now) A simple multi-provider Internet 1 The Global Internet Some

More information

BGP Protocol & Configuration. Scalable Infrastructure Workshop AfNOG2008

BGP Protocol & Configuration. Scalable Infrastructure Workshop AfNOG2008 BGP Protocol & Configuration Scalable Infrastructure Workshop AfNOG2008 Border Gateway Protocol (BGP4) Case Study 1, Exercise 1: Single upstream Part 6: BGP Protocol Basics Part 7: BGP Protocol - more

More information

Border Gateway Protocol

Border Gateway Protocol 39 CHAPTER Chapter Goals Understand the purpose of the. Explain BGP attributes and their use in route selection. Examine the BGP route selection process. Introduction The (BGP) is an interautonomous system

More information

Connecting to a Service Provider Using External BGP

Connecting to a Service Provider Using External BGP Connecting to a Service Provider Using External BGP First Published: May 2, 2005 Last Updated: August 21, 2007 This module describes configuration tasks that will enable your Border Gateway Protocol (BGP)

More information

Inter-AS routing and BGP. Network Layer 4-1

Inter-AS routing and BGP. Network Layer 4-1 Inter-AS routing and BGP Network Layer 4-1 Review: intra-as routing v Also known as interior gateway protocols (IGP) v Most common intra-as routing protocols: RIP: Routing Information Protocol, distance

More information

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355 BGP Commands Use the commands in this chapter to configure and monitor Border Gateway Protocol (BGP). For BGP configuration information and examples, refer to the Configuring BGP chapter of the Network

More information

Routing on the Internet. Routing on the Internet. Hierarchical Routing. Computer Networks. Lecture 17: Inter-domain Routing and BGP

Routing on the Internet. Routing on the Internet. Hierarchical Routing. Computer Networks. Lecture 17: Inter-domain Routing and BGP Routing on the Internet Computer Networks Lecture 17: Inter-domain Routing and BGP In the beginning there was the ARPANET: route using GGP (Gateway-to-Gateway Protocol), a distance vector routing protocol

More information

CS519: Computer Networks. Lecture 4, Part 5: Mar 1, 2004 Internet Routing:

CS519: Computer Networks. Lecture 4, Part 5: Mar 1, 2004 Internet Routing: : Computer Networks Lecture 4, Part 5: Mar 1, 2004 Internet Routing: AS s, igp, and BGP As we said earlier, the Internet is composed of Autonomous Systems (ASs) Where each AS is a set of routers, links,

More information

Chapter 4: Network Layer

Chapter 4: Network Layer Chapter 4: Network Layer 4. 1 Introduction 4.2 Virtual circuit and datagram networks 4.3 What s inside a router 4.4 IP: Internet Protocol Datagram format IPv4 addressing ICMP IPv6 4.5 Routing algorithms

More information

Connecting to a Service Provider Using External BGP

Connecting to a Service Provider Using External BGP Connecting to a Service Provider Using External BGP This module describes configuration tasks that will enable your Border Gateway Protocol (BGP) network to access peer devices in external networks such

More information

Cisco Performance Routing

Cisco Performance Routing Cisco Performance Routing As enterprise organizations grow their businesses, the demand for real-time application performance and a better application experience for users increases. For example, voice

More information

COMP211 Chapter 5 Network Layer: The Control Plane

COMP211 Chapter 5 Network Layer: The Control Plane COMP211 Chapter 5 Network Layer: The Control Plane All material copyright 1996-2016 J.F Kurose and K.W. Ross, All Rights Reserved Computer Networking: A Top Down Approach 7 th edition Jim Kurose, Keith

More information

Department of Computer and IT Engineering University of Kurdistan. Computer Networks II Border Gateway protocol (BGP) By: Dr. Alireza Abdollahpouri

Department of Computer and IT Engineering University of Kurdistan. Computer Networks II Border Gateway protocol (BGP) By: Dr. Alireza Abdollahpouri Department of Computer and IT Engineering University of Kurdistan Computer Networks II Border Gateway protocol (BGP) By: Dr. Alireza Abdollahpouri Internet structure: network of networks local ISP Tier

More information

Chapter 4: Network Layer, partb

Chapter 4: Network Layer, partb Chapter 4: Network Layer, partb The slides are adaptations of the slides available by the main textbook authors, Kurose&Ross Network Layer 4-1 Interplay between routing, forwarding routing algorithm local

More information

Internet Interconnection Structure

Internet Interconnection Structure Internet Interconnection Structure Basic Concepts (1) Internet Service Provider (ISP) Provider who connects an end user customer with the Internet in one or few geographic regions. National & Regional

More information

CSCE 463/612 Networks and Distributed Processing Spring 2018

CSCE 463/612 Networks and Distributed Processing Spring 2018 CSCE 463/612 Networks and Distributed Processing Spring 2018 Network Layer V Dmitri Loguinov Texas A&M University April 17, 2018 Original slides copyright 1996-2004 J.F Kurose and K.W. Ross Chapter 4:

More information

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355 BGP Commands Use the commands in this chapter to configure and monitor Border Gateway Protocol (BGP). For BGP configuration information and examples, refer to the Configuring BGP chapter of the Network

More information

Routing on the Internet! Hierarchical Routing! The NSFNet 1989! Aggregate routers into regions of autonomous systems (AS)!

Routing on the Internet! Hierarchical Routing! The NSFNet 1989! Aggregate routers into regions of autonomous systems (AS)! Routing on the Internet! Hierarchical Routing! Aggregate routers into regions of autonomous systems (AS)! In the beginning there was the ARPANET:! route using GGP (Gateway-to-Gateway Protocol)," a distance

More information

BGP made easy. John van Oppen Spectrum Networks / AS11404

BGP made easy. John van Oppen Spectrum Networks / AS11404 1 BGP made easy John van Oppen Spectrum Networks / AS11404 2 What is BGP? Snarky answer: RFC-4271 BGP is an Exterior gateway protocol, the only one used on the public Internet and is used for inter-autonomous

More information

CSCE 463/612 Networks and Distributed Processing Spring 2018

CSCE 463/612 Networks and Distributed Processing Spring 2018 CSCE 463/612 Networks and Distributed Processing Spring 2018 Network Layer IV Dmitri Loguinov Texas A&M University April 12, 2018 Original slides copyright 1996-2004 J.F Kurose and K.W. Ross 1 Chapter

More information

Announcements. CS 5565 Network Architecture and Protocols. Project 2B. Project 2B. Project 2B: Under the hood. Routing Algorithms

Announcements. CS 5565 Network Architecture and Protocols. Project 2B. Project 2B. Project 2B: Under the hood. Routing Algorithms Announcements CS 5565 Network Architecture and Protocols Lecture 20 Godmar Back Project 2B due in 2 parts: Apr 29 and May 6 Extra Credit Opportunities: Expand simulator (and your implementation) to introduce

More information

Other Developments: CIDR

Other Developments: CIDR Other Developments: CIDR CIDR (classless Inter domain routing) Too many small networks requiring multiple class C addresses Running out of class B addresses, not enough nets in class A Assign contiguous

More information

Implementing BGP. BGP Functional Overview. Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create loop-free

Implementing BGP. BGP Functional Overview. Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create loop-free Border Gateway Protocol (BGP) is an Exterior Gateway Protocol (EGP) that allows you to create loop-free interdomain routing between autonomous systems. An autonomous system is a set of routers under a

More information

cs/ee 143 Communication Networks

cs/ee 143 Communication Networks cs/ee 143 Communication Networks Chapter 5 Routing Text: Walrand & Parakh, 2010 Steven Low CMS, EE, Caltech Warning These notes are not self-contained, probably not understandable, unless you also were

More information

Advanced Multihoming. BGP Traffic Engineering

Advanced Multihoming. BGP Traffic Engineering Advanced Multihoming BGP Traffic Engineering 1 Service Provider Multihoming Previous examples dealt with loadsharing inbound traffic Of primary concern at Internet edge What about outbound traffic? Transit

More information

ISP Border Definition. Alexander Azimov

ISP Border Definition. Alexander Azimov ISP Border Definition Alexander Azimov ISP goal (one ASN) BGP Decision Process Step Attribute Transit 1 Highest Local Preference value Non-transit 2 Lowest AS Path length Transit 3 Lowest

More information

THE INTERNET connects thousands of Autonomous

THE INTERNET connects thousands of Autonomous IEEE/ACM TRANSACTIONS ON NETWORKING, VOL. 9, NO. 6, DECEMBER 2001 681 Stable Internet Routing Without Global Coordination Lixin Gao, Member, IEEE, and Jennifer Rexford, Senior Member, IEEE Abstract The

More information

5.1 introduction 5.5 The SDN control 5.2 routing protocols plane. Control Message 5.3 intra-as routing in Protocol the Internet

5.1 introduction 5.5 The SDN control 5.2 routing protocols plane. Control Message 5.3 intra-as routing in Protocol the Internet Chapter 5: outline 5.1 introduction 5.5 The SDN control 5.2 routing protocols plane link state 5.6 ICMP: The Internet distance vector Control Message 5.3 intra-as routing in Protocol the Internet t 5.7

More information

Multihoming Complex Cases & Caveats

Multihoming Complex Cases & Caveats Multihoming Complex Cases & Caveats ISP Workshops Last updated 6 October 2011 Complex Cases & Caveats p Complex Cases n Multiple Transits n Multi-exit backbone n Disconnected Backbone n IDC Multihoming

More information

Inter-Domain Routing: BGP

Inter-Domain Routing: BGP Inter-Domain Routing: BGP Stefano Vissicchio UCL Computer Science CS 3035/GZ01 Agenda We study how to route over the Internet 1. Context The Internet, a network of networks Relationships between ASes 2.

More information

Implementation of BGP in a Network Simulator

Implementation of BGP in a Network Simulator Implementation of BGP in a Network Simulator Tony Dongliang Feng Rob Ballantyne Ljiljana Trajković Communication Networks Laboratory http://www.ensc.sfu.ca/cnl Simon Fraser University Road map Introduction

More information

Hierarchical Routing. Our routing study thus far - idealization all routers identical network flat not true in practice

Hierarchical Routing. Our routing study thus far - idealization all routers identical network flat not true in practice Hierarchical Routing Our routing study thus far - idealization all routers identical network flat not true in practice scale: with 200 million destinations: can t store all destinations in routing tables!

More information

Hierarchical Routing. Our routing study thus far - idealization all routers identical network flat not true in practice

Hierarchical Routing. Our routing study thus far - idealization all routers identical network flat not true in practice Hierarchical Routing Our routing study thus far - idealization all routers identical network flat not true in practice scale: with 200 million destinations: can t store all destinations in routing tables!

More information

Architectures and Protocols for Integrated Networks. Intra-domain and Inter-domain Routing Protocols

Architectures and Protocols for Integrated Networks. Intra-domain and Inter-domain Routing Protocols Architectures and Protocols for Integrated Networks Intra-domain and Inter-domain Routing Protocols How is the routing table built? Path finding Paths from a device to any other device. Aggregated according

More information

BGP Routing inside an AS

BGP Routing inside an AS Hot Potatoes Heat Up BGP Routing Renata Teixeira (UC San Diego) http://www-cse.ucsd.edu/~teixeira with Aman Shaikh (AT&T), Tim Griffin(Intel), and Jennifer Rexford(AT&T) 30 th NANOG Miami, Florida BGP

More information

BGP can also be used for carrying routing information for IPv6 prefix over IPv6 networks.

BGP can also be used for carrying routing information for IPv6 prefix over IPv6 networks. This chapter describes how to configure the Cisco ASA to route data, perform authentication, and redistribute routing information using the Border Gateway Protocol (). About, page 1 Guidelines for, page

More information

A Measurement Study on the Impact of Routing Events on End-to-End Internet Path Performance

A Measurement Study on the Impact of Routing Events on End-to-End Internet Path Performance A Measurement Study on the Impact of Routing Events on End-to-End Internet Path Performance Feng Wang University of Mass., Amherst fewang@ecs.umass.edu Zhuoqing Morley Mao University of Michigan zmao@eecs.umich.edu

More information

Introduction to IP Routing. Geoff Huston

Introduction to IP Routing. Geoff Huston Introduction to IP Routing Geoff Huston Routing How do packets get from A to B in the Internet? A Internet B Connectionless Forwarding Each router (switch) makes a LOCAL decision to forward the packet

More information

CSC 4900 Computer Networks: Routing Protocols

CSC 4900 Computer Networks: Routing Protocols CSC 4900 Computer Networks: Routing Protocols Professor Henry Carter Fall 2017 Last Time Link State (LS) versus Distance Vector (DV) algorithms: What are some of the differences? What is an AS? Why do

More information

Network Protocols. Routing. TDC375 Winter 2002 John Kristoff - DePaul University 1

Network Protocols. Routing. TDC375 Winter 2002 John Kristoff - DePaul University 1 Network Protocols Routing TDC375 Winter 2002 John Kristoff - DePaul University 1 IP routing Performed by routers Table (information base) driven Forwarding decision on a hop-by-hop basis Route determined

More information

Network-Wide Prediction of BGP Routes

Network-Wide Prediction of BGP Routes Network-Wide Prediction of BGP Routes Nick Feamster Jennifer Rexford Georgia Tech Princeton University feamster@cc.gatech.edu jrex@cs.princeton.edu Abstract This paper presents provably correct algorithms

More information

Internet rou)ng. V. Arun CS491G: Computer Networking Lab University of MassachuseFs Amherst

Internet rou)ng. V. Arun CS491G: Computer Networking Lab University of MassachuseFs Amherst Internet rou)ng V. Arun CS491G: Computer Networking Lab University of MassachuseFs Amherst Slide material copyright 1996-2013 J.F Kurose and K.W. Ross, All Rights Reserved Graph abstraction 5 graph: G

More information

Interdomain routing with BGP4 Part 4/5

Interdomain routing with BGP4 Part 4/5 Interdomain routing with BGP4 Part 4/5 Olivier Bonaventure Department of Computing Science and Engineering Université catholique de Louvain (UCL) Place Sainte-Barbe, 2, B-1348, Louvain-la-Neuve (Belgium)

More information

Advanced Computer Networks

Advanced Computer Networks Advanced Computer Networks External Routing - BGP protocol Prof. Andrzej Duda duda@imag.fr http://duda.imag.fr Contents Principles of Inter-Domain Routing Autonomous systems Path vector routing Policy

More information

Introduction to BGP. ISP Workshops. Last updated 30 October 2013

Introduction to BGP. ISP Workshops. Last updated 30 October 2013 Introduction to BGP ISP Workshops Last updated 30 October 2013 1 Border Gateway Protocol p A Routing Protocol used to exchange routing information between different networks n Exterior gateway protocol

More information

DATA COMMUNICATOIN NETWORKING

DATA COMMUNICATOIN NETWORKING DATA COMMUNICATOIN NETWORKING Instructor: Ouldooz Baghban Karimi Course Book & Slides: Computer Networking, A Top-Down Approach By: Kurose, Ross Introduction Course Overview Basics of Computer Networks

More information

CSCI-1680 Network Layer: Inter-domain Routing Rodrigo Fonseca

CSCI-1680 Network Layer: Inter-domain Routing Rodrigo Fonseca CSCI-1680 Network Layer: Inter-domain Routing Rodrigo Fonseca Based partly on lecture notes by Rob Sherwood, David Mazières, Phil Levis, John Janno? Today Last time: Intra-Domain Routing (IGP) RIP distance

More information

Introduction to BGP ISP/IXP Workshops

Introduction to BGP ISP/IXP Workshops Introduction to BGP ISP/IXP Workshops 1 Border Gateway Protocol Routing Protocol used to exchange routing information between networks exterior gateway protocol RFC1771 work in progress to update draft-ietf-idr-bgp4-18.txt

More information

Dynamic Routing. The Protocols

Dynamic Routing. The Protocols Dynamic Routing The Protocols Desirable Characteristics of Dynamic Routing Automatically detect and adapt to topology changes Provide optimal routing Scalability Robustness Simplicity Rapid convergence

More information

BGP Diverse Path Using a Diverse-Path Route Reflector

BGP Diverse Path Using a Diverse-Path Route Reflector BGP Diverse Path Using a Diverse-Path Route Reflector The feature allows Border Gateway Protocol (BGP) to distribute an alternative path other than the best path between BGP speakers when route reflectors

More information

BGP Additional Paths. Finding Feature Information. Information About BGP Additional Paths. Problem That Additional Paths Can Solve

BGP Additional Paths. Finding Feature Information. Information About BGP Additional Paths. Problem That Additional Paths Can Solve The feature allows the advertisement of multiple paths through the same peering session for the same prefix without the new paths implicitly replacing any previous paths. This behavior promotes path diversity

More information

BGP Attributes and Policy Control

BGP Attributes and Policy Control BGP Attributes and Policy Control ISP/IXP Workshops 1 Agenda BGP Attributes BGP Path Selection Applying Policy 2 BGP Attributes The tools available for the job 3 What Is an Attribute?... Next Hop......

More information

Introduction to BGP. ISP/IXP Workshops

Introduction to BGP. ISP/IXP Workshops Introduction to BGP ISP/IXP Workshops 1 Border Gateway Protocol A Routing Protocol used to exchange routing information between different networks Exterior gateway protocol Described in RFC4271 RFC4276

More information

Stable Internet Route Selection

Stable Internet Route Selection Stable Internet Route Selection Brighten Godfrey Matthew Caesar Ian Haken Scott Shenker Ion Stoica UC Berkeley pbg@cs.berkeley.edu NANOG 40 June 6, 2007 BGP instability: trouble control plane data plane

More information

BGP. Inter-domain routing with the Border Gateway Protocol. Iljitsch van Beijnum Amsterdam, 13 & 16 March 2007

BGP. Inter-domain routing with the Border Gateway Protocol. Iljitsch van Beijnum Amsterdam, 13 & 16 March 2007 BGP Inter-domain routing with the Border Gateway Protocol Iljitsch van Beijnum Amsterdam, 13 & 16 March 2007 1 Routing Between ISPs Internal routing protocols don't work here: too much information So:

More information

Chapter 4 Network Layer

Chapter 4 Network Layer Chapter 4 Network Layer A note on the use of these ppt slides: We re making these slides freely available to all (faculty, students, readers). They re in PowerPoint form so you see the animations; and

More information

BGP Tutorial. APRICOT 2003, Taipei February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved.

BGP Tutorial. APRICOT 2003, Taipei February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved. BGP Tutorial Philip Smith , Taipei February 2003 1 APRICOT BGP Tutorials Four Tutorials over Two Days Part 1 Introduction Monday morning Part 2 Deployment Monday afternoon Part 3 Multihoming

More information

CS 557 BGP Convergence

CS 557 BGP Convergence CS 557 BGP Convergence Improved BGP Convergence via Ghost Flushing Bremler-Barr, fek, Schwarz, 2003 BGP-RCN: Improving Convergence Through Root Cause Notification Pei, zuma, Massey, Zhang, 2005 Spring

More information

BGP Multihoming ISP/IXP Workshops

BGP Multihoming ISP/IXP Workshops BGP Multihoming ISP/IXP 1 Why Multihome? Redundancy One connection to internet means the network is dependent on: Local router (configuration, software, hardware) WAN media (physical failure, carrier failure)

More information

Multiprotocol BGP (MBGP)

Multiprotocol BGP (MBGP) Multiprotocol BGP (MBGP) Module 5 2000, Cisco Systems, Inc. 1 Copyright 1998-2000, Cisco Systems, Inc. Module5.ppt 1 Module Objectives Understand that MBGP is NOT a replacement for PIM Understand the basic

More information

Introduction to Routing

Introduction to Routing 1 Introduction to Routing Session 2 Presentation_ID.scr 1 Agenda Addressing Concepts Routing Protocols Statics and Defaults 3 ISO OSI Reference Model Routing Information Protocol (RIP and RIPv2) L7 L6

More information

BGP Tutorial. APRICOT 2004, Kuala Lumpur February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved.

BGP Tutorial. APRICOT 2004, Kuala Lumpur February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved. BGP Tutorial Philip Smith , Kuala Lumpur February 2004 1 APRICOT BGP Tutorials Two Tutorials Part 1 Introduction Part 2 Multihoming Morning Afternoon 2 BGP Tutorial Part 1 Introduction Philip

More information

L11 : Inter-domain Routing with BGP Lecture14 Michaelmas, 2016

L11 : Inter-domain Routing with BGP Lecture14 Michaelmas, 2016 7//06 L : Inter-domain Routing with BGP Lecture4 Michaelmas, 06 Timothy G. Griffin Computer Lab Cambridge UK 7//06 How many ASNs today (7 November, 06)? http://bgp.potaroo.net/ 7//06 How many prefixes

More information

BGP Best External. Finding Feature Information

BGP Best External. Finding Feature Information The feature provides the network with a backup external route to avoid loss of connectivity of the primary external route. The feature advertises the most preferred route among those received from external

More information

Introduction to routing

Introduction to routing DD2490 p4 2010 Introduction to routing Olof Hagsand KTH/CSC Network example: KTH Intranet Levels of abstraction The Internet is huge Necessary to divide the routing problem into sub-problems. There are

More information

Network Layer: Control Plane 5-2

Network Layer: Control Plane 5-2 Network Laer: Control Plane EECS34 8-03-05 4- Chapter 5: network laer control plane chapter goals: understand principles behind network control plane traditional routing algorithms SDN controlllers Internet

More information

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 14

CMPE 150/L : Introduction to Computer Networks. Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 14 CMPE 150/L : Introduction to Computer Networks Chen Qian Computer Engineering UCSC Baskin Engineering Lecture 14 1 Two notes on routing algorithm Do not believe ou can understand an routing protocol, e.g.,

More information

Delayed Internet Routing Convergence

Delayed Internet Routing Convergence Delayed Internet Routing Convergence Craig Labovitz Microsoft Research One Microsoft Way Redmond, WA 98052-63999 labovit@microsoft.com Abha Ahuja, Abhijit Bose Farnam Jahanian University of Michigan Department

More information

Routing Protocols of IGP. Koji OKAMURA Kyushu University, Japan

Routing Protocols of IGP. Koji OKAMURA Kyushu University, Japan Routing Protocols of IGP Koji OKAMURA Kyushu University, Japan Routing Protocol AS (Autonomous System) Is operated autonomous in the organization. 6bit IGP (Interior Gateway Protocol) Routing Control inside

More information

Exterior Gateway Protocols: EGP, BGP-4, CIDR

Exterior Gateway Protocols: EGP, BGP-4, CIDR Exterior Gateway Protocols: EGP, BGP-4, CIDR shivkuma@ecse.rpi.edu http://www.ecse.rpi.edu/homepages/shivkuma Based in part upon slides of Tim Griffin (AT&T), Ion Stoica (UCB), J. Kurose (U Mass), Noel

More information

Lecture 4. The Network Layer (cont d)

Lecture 4. The Network Layer (cont d) Lecture 4 The Network Layer (cont d) Agenda Routing Tables Unicast and Multicast Routing Protocols Routing Algorithms Link State and Distance Vector Routing Information and Open Shortest Path First Protocols

More information

Configuring Advanced BGP

Configuring Advanced BGP CHAPTER 6 This chapter describes how to configure advanced features of the Border Gateway Protocol (BGP) on the Cisco NX-OS switch. This chapter includes the following sections: Information About Advanced

More information