Towards an Accurate AS-level Traceroute Tool

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Transcript Towards an Accurate AS-level Traceroute Tool 

Inter-domain Routing:
Today and Tomorrow
Dr. Jia Wang
[email protected]
AT&T Labs Research
Florham Park, NJ 07932, USA
http://www.research.att.com/~jiawang/
Prof. Zhuoqing Morley Mao
[email protected]
Department of EECS
University of Michigan
Ann Arbor, MI 48109, USA
http://www.eecs.umich.edu/~zmao/
IEEE INFOCOM 2004 Tutorial
March 8, 2004
Outline
1.
2.
3.
4.
5.
6.
7.
Overview of Inter-domain routing
Routing policies
Measuring inter-domain paths
Routing instability
BGP Beacon - measurement infrastructure
Implication on network engineering
Security issues
Our opinions should not be taken to represent AT&T policies
March 8, 2004
2
Part I: Overview of Interdomain Routing
Internet
 Loose cooperative effort of Internet
Service Providers (ISPs)
 E.g., AT&T, Sprint, UUNet, AOL
 Best effort service
 Connectedness
 Anyone connected to the Internet can
exchange traffic with anyone else
connected to the Internet
March 8, 2004
4
Internet routing
routes
Control plane:
exchange routes
Internet
: Routing session
Data plane:
forward traffic
IP traffic
rusty.cs.berkeley.edu
IP=169.229.62.116
Prefix=169.229.0.0/16
March 8, 2004
www.cnn.com
IP=64.236.16.52
Prefix=64.236.16.0/20
5
Internet routing dictates
application performance
routes
Control plane:
exchange routes
: Routing session
Internet
Data plane:
forward traffic
IP traffic
rusty.cs.berkeley.edu
IP=169.229.62.116
Prefix=169.229.0.0/16
March 8, 2004
Fail over to alternate route
www.cnn.com
IP=64.236.16.52
Prefix=64.236.16.0/20
6
Internet routing domain
 Network devices under same technical
and administrative control
 Common routing policy
 E.g., ISPs, enterprise networks
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7
Autonomous System (AS)
 Autonomous routing domain with an AS
number (ASN)
 AS numbers




16 bits integer
Public AS number: 1 – 64511
Private AS number: 64512 – 65535
Examples
 AT&T: 7018, 6431, …
 Sprint: 1239, 1240, …
 MIT: 3
March 8, 2004
8
More than 14,000 ASes today
Internet
Autonomous
System
ISP
Level3
Calren
Berkeley
March 8, 2004
ISP
ISP
Qwest
ISP
Business
business
ISP
ISP
AT&T
Sprint UUnet
ISP
ISP
IP traffic
University
Company
company
GNN
CNN
9
Internet Initiative Japan (IIJ)
March 8, 2004
10
IIJ, Tokyo
March 8, 2004
11
Telstra international
March 8, 2004
12
WorldCom (UUNet)
March 8, 2004
13
UUNet, Europe
March 8, 2004
14
Sprint, USA
March 8, 2004
15
AT&T IP Backbone, USA
Anchorage,
AK
Year end 2001
Seattle Spokane
Portland
Portland Worcester
Manchester
Minneapolis
R
St. Paul
Milwaukee
Madison
Des
Moines
Sacramento
R
San
Las
Vegas
San
Francisco
Francisco
Oakland
Redwood
City
LAAirport
Blvd
Kansas
City
Colorado
Springs
Angeles
Albuquerque
San
Bernardino
Garden
a
St Louis
Oklaho
ma
City
R R
Buffalo
Harrisbu
rg
Detroit
Plymouth
Wash Phil
.DC
Louisville
Nashville
Tulsa
NY
C
R
BaltimoreNewark
Bohemia
White
Brunswick
Plains
Cedar
Knolls
Rochelle Pk
Hamilton
Square
Freehold
R
NYC-
R
Norfolk Camden,
NJ
Richmond
Bdwy
Raleigh
Greensboro
Charlotte
Little Rock
Memphis
Backbone Node
Remote GSR Access Router
Remote Access Router
March 8, 2004
Cambridge
Hartford
Framingham
Wayn
StamfordProvidence
Providence
Bridgepo
e
rt New
Florissant
Phoenix
Gateway Node
N X DS3
N X OC3
N X OC12
N X OC48
NX OC192
Grand
RapidsBirmingham
Pittsburgh
South Bend ClevelandAkron
Chicago
DaytoColumbus Silver
Springs
n
Indianapolis
Arlington
Cincinnati
R
Anaheim
San Diego
R
R
Albany
Syracuse
Rochester
Rolling
Meadows
Oak
Davenport Brook
Chicag
o
Omaha
Denver
R San Jose
Los
Sherman Oaks
Honolulu
R
Salt Lake
City
Glenvie
w
Ft. Worth
Birmingham
Norcross
Columbia
Dunwoody
Atlanta
Dallas
Jacksonville
New Orleans
Austin
Orlando
Houston
San Antonio
R
Note: Connectivity
and nodes shown are
targeted for
deployment; actual
deployment
may vary. Maps
should not be used to
predict service
availability.
Tampa
R
Ft.
Lauderdale
W. Palm Beach
Ft.
Ojus
Lauderdale
Miami
San Juan PR
Rev. 6-4-01
16
GARR-B
March 8, 2004
17
Gigabit research network
March 8, 2004
18
wiscnet.net
UW-Superior
Rice Lake
Rhinelander
UW-Stout
Marshfield
UW-River Falls
Stiles
Jct.
Wausau
UW-Eau Claire
Qwest
and Other
Provider(s)
Clintonville
er '02)
(Summ
UW-Stevens Point
UW-Green Bay
(Summer
'02)
Fox Valley TC
(Summer '03)
um
(S
UW-Oshkosh
m
'
er
)
02
UW-La Crosse
La Crosse
Portage
Dodgeville
GO BUCKY!
Genuity
UW-Madison
(Summer '03)
UW-Milwaukee
UW-Whitewater
UW-Parkside
)
(Winter '02
UW-Platteville
Gigabit Ethernet
OC-12 (622Mbps)
OC-3 (155Mbps)
DS-3 (45Mbps)
T1 (1.5Mbps)
March 8, 2004
Chicago






Internet 2
& Qwest
Peering - Public and Private
Commodity Internet Transit
Internet2
Merit and Other State Networks
National Education Network
Regional Research Peers
2
ter '0
(Win
)
Chicago - 2
(Winter '02)
Chicago - 1
19
MIT.edu
http://bgp.lcs.mit.edu/
March 8, 2004
20
Internet routing architecture
Intra-domain
routing
Calren
Berkeley
March 8, 2004
Level3
IP traffic
Internet
Inter-domain
routing
GNN
CNN
21
Intra-domain routing
 Run within a certain network infrastructure
 Optimize routes taken between points within
a network
 Internal Gateway Protocols (IGPs)




Metrics based
OSPF (Open Shortest Path First)
RIP (Routing Information Protocol)
IS-IS (Intermediate System to Intermediate
System)
March 8, 2004
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Inter-domain routing
 Run between networks
 Provide full connectivity of entire
Internet
 External Gateway Protocol (EBGP)
 Policy based
 BGP (Border Gateway Protocol)
March 8, 2004
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Inter-domain routing and BGP
 Static routing
 Mainly for stub networks
 Default routing
 Small stub networks
 Dynamic routing
 Via BGP
No need to run BGP in static routing and default routing.
March 8, 2004
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Link state
 Examples: OSPF, IS-IS
 Based on Dijkstra’s shortest path computation
 Each router periodically floods immediate
reachability information to other routers
 Fast convergence
 High communication and computation
overhead
 Not scalable for large networks
 Requires periodic refreshes
March 8, 2004
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Vectoring
 Distance vs. Path Vector
 Distance: hop count (RIP)
 Path: entire path (BGP)
 Helps identify loops
 Supports policy-based routing based on path
 Minimal communication overhead
 Takes longer to converge, i.e., in
proportion to the maximum path length
March 8, 2004
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Link state vs. vectoring
Link state Vectoring
IGP
EGP
OSPF
IS-IS
RIP
BGP
BGP is a path vector protocol
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Classful addressing
 IPv4: 32 bits
 Five classes of networks
Class
Address
Mask
# of networks # of hosts
A
0*
255.0.0.0
128
~1.6M
B
10*
255.255.0.0
16384
65535
C
110*
255.255.255.0
~2.1M
255
D
Used for multicast
E
Reserved and currently unused
Improve scaling factor of routing in the Internet => classless
March 8, 2004
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RFC1519: Classless Inter-domain
Routing (CIDR)
 No implicit mask based on the class of
the network
 Explicit masks passed in the routing
protocol
 Allow aggregation and hierarchical
routing
March 8, 2004
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CIDR addressing
IP address: 12.70.0.0 Mask: 255.255.252.0
Address
Mask
00001100 00100110 00000000 00000000
11111111 11111111 11000000 00000000
Network prefix
Host
identifier
CIDR representation: 12.70.0.0/22
March 8, 2004
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Address aggregation
12.70.0.0/24
12.70.1.0/24
12.70.2.0/24
March 8, 2004
12.70.3.0/24
Internet
ISP A
12.71.0.0/16
ISP B
12.70.0.0/22
12.71.0.0/16
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Routing and forwarding
 Routing
 The decision process of choosing optimal
path that is consistent with the
administrative or technical policy
 Forwarding
 The act of receiving a packet, doing a
lookup, and copying a packet to the next
hop
March 8, 2004
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Classless forwarding
Internet
12.70.0.20
10.20.128.10
10.20.128.1
10.20.0.1
IP traffic
10.20.1.1
135.120.0.1
March 8, 2004
Prefix
12.70.0.0/24
12.70.0.0/16
12.0.0.0/8
0.0.0.0
Next hop
10.20.0.1
10.20.1.1
10.20.128.1
10.20.128.10
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Inter-domain routing with CIDR
support
 BGP-4 [RFC1771]





De facto EGP
Path vector protocol
Run on top of TCP for reliability
Carry routing information between ASes
Policy based routing
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BGP basic operations
 Set up BGP session
 Exchange all candidate routes
 Send incremental updates
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Establish BGP session
Establish neighboring session
between 12.10.0.1 and 12.10.0.2
12.10.0.1
Prefix
135.120.0.0/24
68.35.0.0/16
March 8, 2004
TCP 179
Next hop
10.128.0.1
10.192.1.1
12.10.0.2
Prefix
12.70.0.0/24
12.9.0.0/16
Next hop
10.20.0.1
10.20.1.1
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Exchange all candidate routes
12.70.0.0/24
12.9.0.0/16
10.20.0.1
10.20.1.1
12.10.0.1
12.10.0.2
135.120.0.0/24
68.35.0.0/16
Prefix
135.120.0.0/24
68.35.0.0/16
12.70.0.0/24
12.9.0.0/16
March 8, 2004
Next hop
10.128.0.1
10.192.1.1
10.20.0.1
10.20.1.1
10.128.0.1
10.192.1.1
Prefix
12.70.0.0/24
12.9.0.0/16
Next hop
10.20.0.1
10.20.1.1
135.120.0.0/24
68.35.0.0/16
10.128.0.1
10.192.1.1
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Send incremental updates
Withdraw 12.9.0.0/16
12.10.0.1
Prefix
135.120.0.0/24
68.35.0.0/16
12.70.0.0/24
12.9.0.0/16
March 8, 2004
12.10.0.2
Next hop
10.128.0.1
10.192.1.1
10.20.0.1
10.20.1.1
Prefix
12.70.0.0/24
12.9.0.0/16
135.120.0.0/24
68.35.0.0/16
Next hop
10.20.0.1
10.20.1.1
10.128.0.1
10.192.1.1
38
BGP messages
 OPEN: set up a peering session
 UPDATE: announce new routes or
withdraw previously announced routes
 NOTIFICATION: shut down a peering
session
 KEEPALIVE: confirm active connection
at regular interval
March 8, 2004
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Internal vs. external BGP
Internet
E-BGP
I-BGP
AS B
AS C
AS A
March 8, 2004
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I-BGP mesh
E-BGP
update
March 8, 2004
I-BGP update
41
Make I-BGP scale for large AS
 Route reflectors
 Confederations
March 8, 2004
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Route reflector
E-BGP
update
RR
RR
Only best paths
being sent by RR
March 8, 2004
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Confederation
AS 1000
EBGP
March 8, 2004
IBGP
IBGP
AS 65010
AS 65020
EBGP
44
BGP updates
 Three blocks
 Prefix
 Path attributes
 Unreachable routes
March 8, 2004
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BGP attributes
Value Code Reference
1 ORIGIN [RFC1771]
2 AS_PATH [RFC1771]
3 NEXT_HOP [RFC1771]
4 MULTI_EXIT_DISC [RFC1771]
5 LOCAL_PREF [RFC1771]
6 ATOMIC_AGGREGATE [RFC1771]
7 AGGREGATOR [RFC1771]
8 COMMUNITY [RFC1997]
9 ORIGINATOR_ID [RFC1998]
10 CLUSTER_LIST [RFC1998]
11 DPA [Chen]
12 ADVERTISER [RFC1863]
13 RCID_PATH / CLUSTER_ID
[RFC1863]
14 MP_REACH_NLRI [RFC2283]
15 MP_UNREACH_NLRI [RFC2283]
16 EXTENDED COMMUNITIES
[Rosen]
17 NEW_AS_PATH [E.Chen]
18 NEW_AGGREGATOR [E.Chen]
19 SAFI Specific Attribute (SSA)
[Nalawade]
20-254 Unassigned
255 reserved for development
http://www.iana.org/assignments/bgp-parameters
March 8, 2004
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Establish connectivity
Prefix
135.120.0.0/16
AS 3
Next hop AS path
12.10.0.5 2 1
Prefix
135.120.0.0/16
IBGP
Next hop AS path
12.10.0.1 1
12.10.0.6
EBGP
12.10.0.5
AS 1
AS 2
135.120.0.0/16
IBGP
March 8, 2004
EBGP
12.10.0.2
IBGP
12.10.0.1
Prefix
135.120.0.0/16
Next hop AS path
12.10.0.1 1
47
IGP and BGP working together
Prefix
135.120.0.0/16
AS 3
IBGP
Next hop AS path
12.10.0.1 1
Prefix
12.10.0.0/30
135.120.0.0/16
12.10.0.6
Next hop
10.10.0.1
10.10.0.1
EBGP
12.10.0.5
AS 1
12.10.0.1
135.120.0.0/16
EBGP
AS 2
12.10.0.2
IBGP
IBGP
March 8, 2004
10.10.0.1
Prefix
135.120.0.0/16
Next hop AS path
12.10.0.1 1
48