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Routing1
Broadband Network Architectures
Router Design
TEMangir Sp02
TEM 497 Routing2
Outline
Introduction Router Fundamentals Routing Algorithms and Protocols Fast Forwarding Layer-3 Switching IP over WDM
Routing3
Introduction
TEM 497 Routing4
A Fine Distinction
Imprecision surrounds the terms “routing” and “forwarding”
Forwarding is the act of transferring a packet from one interface of a router to another, after consulting a forwarding table
Routing is the act building routing tables by means of a routing algorithm
We frequently abuse this convention
TEM 497 Routing5
What is a Router?
A packet forwarder Multiprotocol – IP, IPX, AppleTalk
A routing-protocol execution machine Multiprotocol – IGRP, RIP, OSPF, IS-IS
A packet monitor A general-purpose computer A firewall A switch
TEM 497 Routing6
Internet Forwarder Functions
Parse the datagram header Checksum actions Select the network protocol Decrement the TTL field Use the TOS field to prioritize the datagram Process the options fields Forward (route) the datagram to next hop Fragment the datagram
TEM 497 Routing7
Internet Router Functions
Execute one or more routing protocols Exchange state information with other routers Use a transport protocol Authentication
Collect network-management statistics Packet counts, lengths, and types Source-destination matrix
Configuration support User interface Tunnel management
TEM 497 Routing8
Internet Firewall Functions
Filtering of destinations Source Destination
Filtering of services Block protocols Block transport port numbers
Virtual private networks Encrypted tunnels
IP
TCP UDP
FTP HTTP X
ProtoID
PortNums
TEM 497 Routing9
Control and Data Planes
RouteDetermination
Function
DataForwarding
Function
Data Plane
Control Plane
control packets to &from other control
plane entities
Router
control packets to &from other controlplane entities
data packets to &from other data
plane entities
data packets to &from other dataplane entities
Routing10
Router Fundamentals
TEM 497 Routing11
ARP
Address Resolution Protocol translates an IP address to a media (link) address
Simple request-response protocol First host broadcasts a request packet
containing desired IP address Second host recognizes its IP address Second host sends a response packet to
first host containing its media (link) address First host caches address mapping for later
use
TEM 497 Routing12
ARP Header
Protocol Type
0 3115
Hardware Type
OperationHLen PLen
Source Hardware Address
Source Protocol Address
Target Hardware Address
Target Protocol Address
TEM 497 Routing13
ARP Header Fields
Hardware type: e.g. Ethernet = 1 Protocol type: e.g. IPv4 = 0080 HLen: Hardware address length (e.g.
Ethernet = 48 bits) PLen: Protocol address length (e.g. IPv4 =
32 bits) Operation: a query (0) or a reply (1) Source: where packet came from Target: system it is querying about
TEM 497 Routing14
ARP Operation (1)
FTP
TCP
IP ARP
DNS
EthernetDriver
ARP
EthernetDriver
TCP
IP ARP
EthernetDriver
(1)(2)
(3) (5)
(4)
(6)(7)(8)
FTP
(8)
(8)
(8)
TEM 497 Routing15
ARP Operation (2)
1. IP datagram with destination address2. Next-hop address is passed to ARP3. ARP request passed to Ethernet driver4. ARP request broadcast in Ethernet frameRouting ARP request recognized by next-hop
node6. ARP reply sent by next-hop node7. ARP reply updates ARP cache8. IP datagram sent through next-hop node
TEM 497 Routing16
Proxy ARP
Allows a router to answer ARP requests from one of its networks for a host on another of its networks
Router substitutes its link address for the responding host’s
Proxy gives the illusion that the host is connected to another network
TEM 497 Routing17
RARP
Reverse ARP translates a media (link) address to an IP address
Used by system without nonvolatile storage
Requires a network-wide RARP server
Similar to BOOTP (Bootstrap Protocol)
TEM 497 Routing18
Router Advertisement (1)
Routers announce presence by broadcasting ICMP router advertisements All-hosts multicast address: 224.0.0.1 Limited broadcast address: Routing
Advertisements are periodic 7-minute period Advertisement becomes stale after 30
minutes
TEM 497 Routing19
Router Advertisement (2)
Advertisements contain a list of addresses Router IP addresses Preference level of each address
Higher values are preferred Highest value is the normal router Lower value is a backup router Lowest values do not wish to receive default
traffic
TEM 497 Routing20
Router Solicitation (1)
A host should not have to wait 7 minutes for the next ICMP router advertisement
ICMP router solicitation messages allow the host to request the identity of a router
The host broadcasts the solicitation All-routers multicast address: 224.0.0.2 Limited broadcast address: 255.255.255.255
The host receives many advertisements The host chooses the router on its subnet
TEM 497 Routing21
Router Solicitation (2)
Host bootstrap operation Broadcasts 3 solicitations Broadcasts 1 message every 3 seconds Broadcasting stops as soon as a valid
router advertisement is received
TEM 497 Routing22
Broadcast Storms
Mechanisms that rely on broadcasting messages within a LAN are vulnerable to broadcast storms, i.e. long, uncontrolled exchanges of broadcast packets.
Because everyone must process a broadcast, storms put a heavy load on uninvolved nodes.
Therefore, protocol exchanges – such as ARP, RARP, DHCP, Router Solicitation, and Router Announcement – must control broadcasts with timers and by limiting message counts.
TEM 497 Routing23
Redirect
ICMP redirect error is sent by a router to a host to indicate that the host should send its datagrams through another router
1. First Datagram
2. Redirect
3. First Datagram
4. Successive Datagrams
Security concern!
TEM 497 Routing24
A Simple Router
MainMemory
CPU NIC
NIC
NIC
I/O Bus
SystemBus
Fast Ethernet
FDDI
ATM
DMAXfer
DMACtrl
NIC = Network Interface ControllerDMA = Direct Memory Access
1. Packet input2. Header processing Routing table lookup DMA transaction3. Packet output
32
1
TEM 497 Routing25
IP Layer
IP-Layer Processing
RoutingTable
ICMP
IP OutputCalculateNext Hop
IP InputQueue
ProcessIP Options
AddressedHere?
TCPUDPRouting
Algorithm
No
Yes
RoutingTable Mgmt
Data
Control
Network Output(s) Network Input(s)
SourceRoutedPacket
ForwardedPacket
TEM 497 Routing26
Routing Table Structure
Destination IPv4 address Host address (32 bits) Network address (<32 bits)
Next-hop router IP address Router on a directly connected network
Flags Network or host Router or interface
Network interface
TEM 497 Routing27
Routing Table
zap % netstat -rnRouting tablesDestination Gateway Flags Refcnt Use Interface128.9.192.24 128.9.112.24 UGH 0 0 myri0128.9.192.72 128.9.112.72 UGH 9 54173 myri0128.9.192.73 128.9.112.73 UGH 0 0 myri0224.0.0.9 127.0.0.1 UH 1 118606 lo0127.0.0.1 127.0.0.1 UH 8 3541986 lo0128.9.192.146 128.9.112.146 UGH 0 0 myri0128.9.192.100 128.9.112.100 UGH 0 0 myri0128.9.192.69 128.9.112.69 UGH 0 0 myri0128.9.192.126 128.9.112.126 UGH 0 0 myri0default 128.9.112.72 UG 22 8601210 myri0128.9.192.0 128.9.192.151 U 7 2109258 le0128.9.112.0 128.9.112.151 U 0 51 myri0
Host address
Network address
Multicast address
Loopback address
Next-hop router
U = route is upG = route is via gatewayH = route is to a hostD = route was redirected
Myrinet
EthernetLoopback
TEM 497 Routing28
IP Output Processing
Search table for match of host address If found, then send datagram to next-hop router
or directly connected interface
Search table for match of network address If found, then send datagram to next-hop router
or directly connected interface Use subnet mask, if necessary
Search table for default entry If found, then send the datagram to next-hop
router
TEM 497 Routing29
Routing
Assumptions Router knows the addresses of all other routers Router knows the “costs” to reach its neighbors
Network viewed as a collection of nodes and (bidirectional) links
From any given router find next hop on shortest path to any other router
Tolerance of failures
TEM 497 Routing30
Distance-Vector Routing
Based on the sharing of distance vectors A router’s distance vector is a list of its
“distances” to every other router in the routing domain
Router tells its neighbors its distance (cost) to every other router in the network
Cost = Distance Usually we assume that cost = distance = hops Other metrics: bandwidth, delay, charging
TEM 497 Routing31
Distance-Vector Algorithm
Router maintains a distance vector List of <dest, cost> entries
Router periodically sends a copy of its distance vector to all neighboring routers
Upon receipt of a distance vector, the router determines its new distance vector cost(v) min {cost(v), costw(v)+cost(w)}
Converges to shortest-path routes O(MN), M=num_links, N=num_nodes
TEM 497 Routing32
Distance-Vector Problems
Slow convergence Packet bouncing after link failure
Counting to infinity Race condition after network partition Algorithm keeps adding to current cost, never
reaching infinity Solution: represent infinity by a large number
Large number is 16 in RIP
Caused by routers repeating information that was valid before failures
TEM 497 Routing33
Link-State Routing
Based on sharing of link state Link-state packets: <ID, Nbr_ID, cost> Link-state information is flooded throughout the
network
Each router computes shortest paths independently
Router tells every other router its distance (cost) to its neighbors
Cost = distance = hops
TEM 497 Routing34
Link-State Algorithm
Router maintains a database of link-state packets that describe its links
Router floods a copy of every link-state packet throughout the network Uses sequence numbers and duplicate elimination
to control the flood
Router applies Dijkstra algorithm to find shortest path
Converges to shortest-path routes O(M logM), M = num_links
TEM 497 Routing35
Two Routing Schemes
Router
DV
DV
DV
Router’sNeighbors
Router All OtherRouters
LSLS
LSLS
Distance Vector RoutingRouter sends a large amount ofinformation to a few recipients
Link State RoutingRouter sends a small amount ofinformation to many recipients
TEM 497 Routing36
Link-State & Distance-Vector Routing
Link-state Loopless routing Fast convergence Precise, multiple metrics (costs)
Distance-vector Simplicity Less memory required
Both in use in today’s Internet
TEM 497 Routing37
Internet Routing Hierarchy
Interior routing Within an AS Intradomain routing
Exterior routing Between ASs Interdomain routing
TEM 497 Routing38
Internet Routing Protocols
Interior Gateway Protocols (IGPs) RIP RIPv2 is the current standard IGRP EIGRP OSPF IS-IS
Exterior Gateway Protocol (EGP) Border Gateway Protocol (BGP) BGP-4 is the current standard
TEM 497 Routing39
Routing Protocol ComparisonRouting Protocol
Supported Protocols
Strengths Limitations
Enhanced IGRP
IP, IPX, AppleTalk
load balancing, metrics
IGRP IP, OSI-IP
RIPv2 IP simplicity improved convergence
OSPF IP rapid convergence
complexity
IS-IS IP, OSI-IP
RIP IP simplicity count to
TEM 497 Routing40
IGP Example
128.9.Routing0/24 (10)
128.9.2.0/24 (2000)
128.9.6.0/24 (10)
128.9.1.0/24 (10)
128.9.1.2 Rtr A
Rtr C
Rtr B 128.9.Routing2
128.9.6.2
128.9.4.0/24 (60)128.9.3.0/24 (60)e0
s1
s2
Destination Next Hop Hop Count129.9.1.0 e0 -128.9.2.0 s1 -128.9.3.0 s2 -
128.9.4.0128.9.2.2 (s1)128.9.3.2 (s2)
11
128.9.Routing0128.9.2.2 (s1) 1128.9.6.0 128.9.3.2 (s2) 1
.2
.2
RIP Routing Table at Rtr ADestination Next Hop Hop Count129.9.1.0 e0 -128.9.2.0 s1 -128.9.3.0 s2 -
128.9.4.0 128.9.3.2 (s2) 120
128.9.Routing0128.9.2.2 (s1) 130128.9.6.0 128.9.3.2 (s2) 70
OSPF Routing Table at Rtr A
TEM 497 Routing41
Lollipop Sequence Space
-N/2 0
N/2 - 1
a
b
d
Sequence numbersstart here (bootup)and circle around
repeatedly
If d<N/4 (halfcircumference) thenb is the newersequence number,otherwise a isnewer
Problem: Sequence numbers of link-state packets wrap around or are restarted
Sequence numbers in this subspace are generatedonly after bootup, and recipients notify the
booting router of last sequence number received
TEM 497 Routing42
Routing in the Internet
Autonomous System (AS) Set of routers and hosts administered
by a single entity Customer network (e.g., 128.9.0.0) ISP Backbone provider
Assigned a unique 16-bit number AS represents a routing domain
TEM 497 Routing43
Classification of ASs (1)
Stub AS Single connection to another AS All traffic is local (i.e., originates or terminates
at the AS) E.g., a typical corporation
Multihomed AS Multiple connections to other ASs Refuses to carry nonlocal (transit) traffic E.g., a well-connected corporation
TEM 497 Routing44
Classification of ASs (2)
Transit AS Multiple connections to other ASs Accepts local and nonlocal (transit)
traffic E.g., ISP or backbone operator
TEM 497 Routing45
Types of ASs
AS 3(transit)
AS 5(stub)
AS 1(transit)
AS 6(multihomed)
AS 2(transit)
AS 4(stub)
TEM 497 Routing46
First 20 AS Numbers
AS Number Name Handle
1 GNTY-1 [CS15-ARIN]2 DCN-AS [DW19-ARIN] 3 MIT-GATEWAYS [RH164-ARIN] 4 ISI-AS [JKR1-ARIN] 5 SYMBOLICS [SG52-ARIN] 6 BULL-HN [JLM23-ARIN] 7 UK-MOD [RNM1-ARIN] 8 RICE-AS [RUH-ORG-ARIN] 9 CMU-ROUTER [HC-ORG-ARIN] 10 CSNET-EXT-AS [CS15-ARIN] 11 HARVARD [WJO3-ARIN] 12 NYU-DOMAIN [ZN68-ARIN] 13 BRL-AS [RR33-ARIN] 14 COLUMBIA-GW [ZC26-ARIN] 15 NET-DYNAMICS-EXP [ZSU-ARIN] 16 LBL [CAL3-ARIN] 17 PURDUE [JRS8-ARIN] 18 UTEXAS [DLN12-ARIN] 19 CSS-DOMAIN [CR11-ARIN] 20 UR [LB16-ARIN]
http://www.arin.net/library/internet_info/asn.txt
TEM 497 Routing47
CIDR — Problems
Classless Interdomain Routing (CIDR) Class A IP addresses are too large (16M hosts) Class C IP addresses are too small (256 hosts) Class B addresses are just right (64K hosts), but
we are running out of class B addresses
Routing table explosion Core routers act upon network numbers Routing tables grow as number of networks
increases
TEM 497 Routing48
CIDR — Solutions
Allocate the class C address space among geographical regions Europe, the Americas, Asia, Africa Eases routing problems
Assign blocks of class C addresses to users Can attach more than 256 hosts Allows for the aggregation of routes
TEM 497 Routing49
CIDR — Rules
User may ask for 2n contiguous class C address blocks (0 n 5) Yields 2n+8 host addresses
A block of class C addresses is listed in a core routing table by address prefix Like a subnet mask E.g., the prefix 192.4.16.0/20 specifies
network numbers 192.4.16.0 through 192.4.31.255
TEM 497 Routing50
CIDR Aggregation
Backbone Provider
ISP
Customer
4096 Customer Addresses192.4.16.0 - 192.4.31.255
192.4.16.0/20
Routing Table
One routingprefix replaces4096 entries
“192.4.16.0/20” is shorthand notation for “192.4.16.0 - 192.4.31.255”
TEM 497 Routing51
CIDR Block Allocations
194.0.0.0 – 195.255.255.255: Europe198.0.0.0 - 199.255.255.255: North America200.0.0.0 - 201. 255.255.255 : Central and South America202.0.0.0 - 203. 255.255.255 : Asia and the Pacific
fewer than 256 addresses: 1 class C networkfewer than 512 addresses: 2 class C networksfewer than 1024 addresses: 4 class C networksfewer than 2048 addresses: 8 class C networksfewer than 4096 addresses:16 class C networksfewer than 8192 addresses:32 class C networksfewer than 16384 addresses:64 class C networks
TEM 497 Routing52
Network Address Translation
A form of IP masquerading Used when a large customer network can
obtain only a small IP address allocation For example, a corporation with thousands of
hosts receives only a class C address space Private network address space used
internally 10.0.0.0/8 172.16.0.0/12 192.168.0.0/16
TEM 497 Routing53
User Tools for Routing
netstat Unix and MS-DOS Display routing table with -rn
arp Unix and MS-DOS Examine or modify the ARP cache
ifconfig Unix Report details of network interfaces with -a
TEM 497 Routing54
Evolution of Router Design
Generation 1: shared backplane and shared buffer memory
Generation 2: shared backplane and local buffer memory
Generation 3: switched backplane and local buffer memory
Generation 4: clusters of routers
TEM 497 Routing55
Generation 1
CPUPACKET
BUFFERS
DMA
MAC
DMA DMA
MAC MAC
LINKINTERFACE
CARDS
BACKPLANEBUS
TEM 497 Routing56
Generation 2
DMA
MAC
DMA DMA
MAC MAC
CPU
PACKETBUFFERS
PACKETBUFFERS
PACKETBUFFERS
LINKINTERFACE
CARDS
BACKPLANEBUS
TEM 497 Routing57
Generation 3
DMA
MAC
DMA DMA
MAC MAC
CPU
PACKETBUFFERS
PACKETBUFFERS
PACKETBUFFERS
LINKINTERFACE
CARDS
SWITCH
TEM 497 Routing58
Generation 4
FAST INTERCONNECT
ROUTER
ROUTER
ROUTER
LINKINTERFACES
Routing59
Fast Forwarding
TEM 497 Routing60
Cisco Forwarding Performance
Switching Path
Cisco 2500
Cisco 4500
Cisco 7000
Cisco 7500
Process 1000 pps10,000
pps2500 pps 10,000 pps
Fast 6000 pps45,000
pps30000 pps
150,000 pps
Hardware N/A N/A271,000
pps275,000
pps
TEM 497 Routing61
Cisco Performance Notes
Process Fast Hardware
TEM 497 Routing62
Importance of Lookups
The routing table must have an entry for every possible Internet address
Routing-table size has grown steadily The problem is to match the destination
address of an incoming packet to a routing-table entry in a small amount of time Entry is usually an aggregated prefix Best (longest) prefix match
TEM 497 Routing63
Routing Table Growth
www.telstra.net/ops/bgptable.html
TEM 497 Routing64
Address Lookup
Router must be able to look up all assigned IPv4 addresses Millions of addresses are assigned
There is not enough high-speed memory to store all assigned IPv4 (and IPv6) addresses
We must aggregate addresses to compress the routing table as much as possible
TEM 497 Routing65
Address Aggregation
128.9.160.38 8
128.9.191.7 8
154.23.16.134 4
194.47.10.72 4
128.12Routing50.89 1
130.39.213.66 1
171.9.160.38 5
193.77.50.7 3
193.9.14.38 5
202.197.160.67 3
Address Interface
128.9.0.0/16 8
128.0.0.0/1 4
128.0.0.0/6 1
171.9.0.0/16 5
193.0.0.0/4 3
193.9.14.0/24 5
Address Interface
Original Table
Compressed Table
TEM 497 Routing66
A Simple Scheme
In IPv4 at most only the first 24 bits are used by core routers Those bits specify the network number toward
which the packet is headed
Given a fast random-access memory of 224 locations (16 Mword), we can store the next hop of net address x.y.z.* in memory location x.y.z
Only one memory access per lookup is needed
TEM 497 Routing67
Updating Routing Tables
Compressed routing tables must be updated periodically
New information about routes can affect address aggregation
The compression effort can be significant
Compression must be computationally efficient
TEM 497 Routing68
Hash Tables for Fast Address Lookup
Length Hash
8
12
16
24
10
10.128, 10.64
10.1, 10.2
10.1.1, 10.1.2, 10.2.1
Lists of Prefixes
TEM 497 Routing69
Level-1 Lookup Scheme
10 162 4
IP Address31 0
bix
ix
bit0 1 15
base[1K]maptable[676]
sixcode[4K] ten
0
675
pointer = + +
TEM 497 Routing70
Level-2/3 Lookup
Level-1 pointer points to either: Next hop, or Indicator to continue search at levels
2/3 Levels 2/3 use the lower 16 bits of
the address to look up the next hop
TEM 497 Routing71
Performance of Scheme
Data structures fit in data cache memory
Fewer than 100 instructions per address are required for lookup
Therefore, can forward several million packets per second through a conventional CPU-based router
Routing72
Layer-3 Switching
TEM 497 Routing73
Tag Switching
Sometimes called layer-3 or IP switching
Combines a switch with a router Fast switch Slower router
Attempts to detour around the slow routing path by taking a fast switching path
TEM 497 Routing74
Observations (ca. 1997)
Routers are expensive and slow $187,000 for 1-Gb/s router
Switches are cheap and fast $41,000 for 5-Gb/s switch
It costs 20 times as much to route a bit as to switch it
TEM 497 Routing75
IP Flows
A flow is a stream of IP packets that follow the same route for several hops
Common flow types Streams from a specific source address to a
specific destination address Streams from a specific source address/port to
a specific destination address/port
Flows have limited lifetimes Analogous to a VC
TEM 497 Routing76
Flow Classification
Flows should be long-lived Disregard DNS packets Disregard ICMP packets (e.g., ping) Disregard most HTTP packets
Flows should be high-throughput Disregard Telnet sessions
Detect a flow if the number of packets received in a specified time interval exceeds a threshold
TEM 497 Routing77
Flow Statistics
Count packets and flows over a period of time Flow is defined by IP source and
destination addresses Measure the duration of each flow Count the number of packets in each
flow
TEM 497 Routing78
Flow Statistics Illustrated
FLOWS
PACKETS
PER
CEN
TA
GE
FLOW DURATION (seconds)
0
0 50 100 150 200 250 300
50
100
TEM 497 Routing79
Flows and Packet TracesProtocol Packets/ s Flows/ s Flow Duration (s) Packets/ Flow
News(NNTP+TCP)
1096 0.7 177 627
Mbone(IP in IP)
456 0.1 173 2307
X Windows(TCP)
111 0.2 161 276
FTP Data(TCP)
2018 2.2 118 525
Rlogin(Telnet+TCP)
803 4.2 114 114
Web(HTTP+TCP)
6717 73.0 57 74
Mail(POP+TCP)
9 0.4 27 21
Mail(SMTP+TCP)
802 49.5 18 15
Management(SNMP+TCP)
43 6.1 18 6
Name Server(DNS+UDP)
929 216.6 15 4
TEM 497 Routing80
Flow Classifier
X/Y flow classifier Flow recognition by stream characteristics
X packets Y seconds Flow is declared switchable
Flow deletion by stream characteristics W packets Z seconds Flow is declared unswitchable
Analogous to calculating first derivative df/dt
TEM 497 Routing81
Basic Tag-Switch Strategy
Determine whether a flow exists Use normal hop-by-hop IP forwarding
for short-lived flows Use “short-cut” ATM switching for
long-lived, high-throughput flows
TEM 497 Routing82
Tag-Switch Architecture
IP SwitchController
ATMSwitch
Remove from ATM switchSignalingLANEMPOAIS-IS routing
Add to ATM switchFlow management protocolSwitch management protocolFlow classifier
Claim: added software is 10% the size of removed software!
TEM 497 Routing83
Default Mode
Controller
Switch
IP flow is initially forwardedTwo default VCs are used
Upstream Downstream
TEM 497 Routing84
Flows Detected
Controller
Switch
Controller detects a flowInstructs upstream switch to use a new VCUpstream flow is now labelled by a new VC
Downstream controller detects a flowInstructs this switch to use a new VCDownstream flow is now labelled by a new VC
Upstream Downstream
TEM 497 Routing85
Cut-Through Action
Controller
Switch
Controller directs the switch to reconfigureTwo VCs are joined into one VCFlow is now carried at switching speedsPeriodic messages to maintain new VCTimeout of inactive flows
Upstream Downstream
TEM 497 Routing86
Features of Tag Switching
IP header and LLC/SNAP encapsulation header can be removed Compression benefits throughput Added back later at the exit tag switch
TTL is adjusted at the exit tag switch Preserve the value that it would have had in
default mode Update the IP checksum too Avoids mismatches in TTL for a flow
TEM 497 Routing87
Tag-Switching Performance
Analysis based on San Francisco NAP packet traces
Evaluate switching gain, i.e. the fraction of all packets that are directly switched
Simulations of Ipsilon IP switch 86% of packets are switched 92% of bytes are switched Switching gain is maximized at a detection
threshold of about 10 packets
TEM 497 Routing88
Layer-3 Switching
Data-driven approaches: use only packet statistics Ipsilon IP Switching Cisco Tag Switching
Topology-driven approaches: use routing-table or other topological information IBM ARIS Multiprotocol Label Switching (MPLS)
TEM 497 Routing89
MPLS
Multiprotocol Label Switching (MPLS) Generalized MPLS (GMPLS)
TEM 497 Routing90
IP over WDM
Place IP flows on their own lightpaths Lightpath is formed by the concatenation of
wavelengths Lightpath is all-optical
Idea is similar to IP switching Wavelength-selective crossconnect (vs. ATM cell
switch) There are only a few wavlelengths to carry flows
(vs. many ATM virtual channels) A signaling protocol is required to set up
lightpaths