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레이블 스위칭 (MPLS) 기술 분석 발표 자료
Analysis on MPLS Technology
December 24, 1998 | By Netmanias (tech@netmanias.com)
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손장우 @ Netmanias (tech@netmanias.com)

 

 

Thank you for visiting Netmanias! Please leave your comment if you have a question or suggestion.
Transcript
1998. 12
넷매니아즈
손장우



Netmanias Confidential

2

Contents

.Motivations for label switching

.Label Switching Approaches

.Cell Switch Router (Toshiba)

.IP Switching (Ipsilon)

.Tag Switching (Cisco)

.ARIS (IBM)

.Comparisons for label switching approaches


.MPLS(MultiProtocol Label Switching)

.Conclusions





Netmanias Confidential

3

“Label Switching”

.Label: short, fixed length identifier. no global significance.

.Forwarding paradigm of Label switching: Label Swapping

.Routing: IP routing protocol(OSPF, BGP,…)


“Layer 3 routing with Layer 2 switching speed”
“switch when you can, route when you must”
“route once, switch many”



Incoming
label

5

7
...

Outgoing
label

3
6

...

Label lookup table(forwarding table)


5


3






Lookup outgoing label

Level swapping
and switching

IP Routing function (OSPF, BGP, PIM, RSVP,...)



Layer 3 router


LDP
Layer 2 switch


Outgoing
interface

1
2

...

i/f1


Netmanias Confidential

4

Motivations for Label Switching

.Growth and Evolution of the Internet

.Integration of IP over ATM

.Extending Routing Functionality





Netmanias Confidential

5




Growth and Evolution of the Internet




Growth
of
Internet

Internet users.

Nodes수.
Need for scalability

Need for
high performance network architecture, switching & routing product
(getting faster!)

Need for new routingfunctionality (paradigm)
BW requirement .


Application (WWW, MM)

Network
Router

Label Switching


Backbone traffic growth has already exccededthe gorwth capabilities of traditional routers-new approaches are required


Router
capacity,
pps

500K

250K

125K

Total internet
backbone
capacity,
TeraBytes/
week

240 TB

60 TB
120 TB

1994

1995
1996

1997




Router capacity
Internet traffic



Netmanias Confidential

6

Need for new routing functionality (paradigm)

Conventional routing architecture: close coupling between routing and forwarding

Routing Table
unicast route{dest IP address, nexthop}
unicast route with TOS{dest IP address, TOS, nexthop}
multicast route{src & dest IP address, nexthop}
CIDR{variable length prefix, nexthop}



Routing function



Forwarding functions(index, algorithm)




IP packet
Longest match, dest IP

exact match, variable length dest IP

Longest match, dest IP & exact match TOS
Next hop

Routing Table
unicast route{dest IP address, nexthop}
unicast route with TOS{dest IP address, TOS, nexthop}
multicast route{src & dest IP address, nexthop}
CIDR{variable length prefix, nexthop}


Forwarding Tableincoming label, outgoing label

IP packet

IP H

Label

IP H




Routing function

Common forwarding
function(label swapping)

Label switching architecture: decoupling between routing and forwarding

Completely decoupling



Netmanias Confidential

7


Integration of IP over ATM

.Data delivery model

.IP: datagram or connectionless model

.ATM: virtual circuit or connection-oriented model

.different addressing scheme, multicast, resource allocation


.How to map the IP architecture onto ATM network: overlay model

.IP network: ATM VC으로interconnected된routers들로구성, IP pkt forwarding

.ATM network: router간에high speed connectivity를제공

.CIOA, LANE, NHRP, MPOA


























IP Network

ATM Network

Router
ATM Switch


























































Netmanias Confidential

8

Integration of IP over ATM

.Problem

.Too many servers: ATM ARP, MARS, NHRP, BUS, Route, Broadcast, ISAG, LECS, default forwarder,…

.Too many protocols: ATM ARP, MARS, NHRP, PNNI, Q.2931,…

.Address resolution

.IP address .ARP .MAC address .LANE server .ATM address .Signaling .VCI .transmit data


.Scalability: N squire full-mesh interconnections are required


.Label switching

.ATM H/W는label(VPI/VCI) swapping방식으로그대로cell forwarding(switching)하고

.forwarding table setup과resource allocation은IP control protocol(BGP,OSPF, RSVP,…)




IP

ATM
ARP

MARS

NHRP

PNNI

Q.2931

ATM H/W
IP routing and
address resolution

ATM signaling
and routing

IP over standard ATM


IP

ATM H/W

LDP

Label switching




LDP:
label distribution protocol



Netmanias Confidential

9

Route Scalability
































































ATM cloud















Router



























































ATM cloud












Router
Switch
























































Router

ATM Switch























































IP Network

ATM Network

.N2mesh connectivity Problem
-A full-mesh of virtual circuit(VCs)
interconnects N routers
-각router간에separate VCC이필요
-VC(Virtual Circuit)의수
= N(N-1)/2 = O(N2).“VC-explosion”
.N2peering Problem
-adjacency 수= N-1
-router의routing computational
overhead = O(N2) .larger, more  
expensive router요구

현재WAN의구조
(Overlay model)
-ATM core network
-Edge routers

ATM cloud에연결된router의수N

.N2mesh connectivity Problem
.VC-merging
.N2peering Problem
LSR .The number of adjacency
dramatically reduce  



Netmanias Confidential

10

Extending Routing Functionality

.Conventional router(routing architecture) ~ destination-based routing (index로destination address만이용하여forwarding한다)

.Policy: Packets arriving from A that are going to router F should go via router D, while all other packets destined for F should go via router E







































Router A

C
B

D

E
F





Netmanias Confidential

11

Label switching approaches

.CSR ~ Toshiba (CSR, FANP: rfc2098, 2129)

.IP switching ~ Ipsilon (GSMP, IFMP: rfc1953, 1954, 1987, 2297)

.Tag switching ~ Cisco (TSR, TDP: rfc2105)

.ARIS(Aggregate Route-based IP Switching) ~ IBM


MPLS (MultiProtocol Label Switching)

.



Netmanias Confidential

12

Cell Switched Router

.CSR ~ Toshiba (CSR, FANP: rfc2098, 2129)

.IP switching ~ Ipsilon (GSMP, IFMP: rfc1953, 1954, 1987, 2297)

.Tag switching ~ Cisco (TSR, TDP: rfc2105)

.ARIS(Aggregate Route-based IP Switching) ~ IBM

.MPLS(MultiProtocol Label Switching)



In spring 1994 : presented IETF IP over ATM WG by Toshibarfc 2098: Toshiba\'s Router Architecture Extensions for ATM : Overview , Feb. 1997rfc 2129: Toshiba\'s Flow Attribute Notification Protocol (FANP) Specification, April 1997LSR(Label Switched Router) = CSR(Cell Switch Router)LDP(Label Distribution Protocol) = FANP(Flow Attribute Notification Protocol)


Netmanias Confidential

13












LANE (LAN Emulation)
.ELAN = VLAN = Broadcast Domain

.ELAN(VLAN)내의communication은LANE을이용해서ATM backbone을통해VCC설정


(LEC, LECS, LES, BUS)
.ELAN(VLAN)간의communication은router를거쳐야한다.

.Routing between ELANs

.one-armed router

.route server






























H


























H




LES


















H






LEC

LEC
LEC

LEC

LAN switch

LAN switch


LES
ELAN 1

ELAN 2



Netmanias Confidential

14
Route
server

One-armedrouter
Routing between ELANs (VLANs)


































H






















H





One-armedrouter

















H






LAN switch

LAN switch

ELAN 1
ELAN 2











Traffic within the same ELAN(A.B)

Traffic between ELANs(A .C)

A

B

C

































H






















H




Route
server
















H






LAN switch

LAN switch
ELAN 1

ELAN 2






Traffic within the same ELAN(A.B)

Traffic between ELANs(A .C)
A


B

C











Address resolution

MPOA




Netmanias Confidential

15
Classical IP over ATM [rfc 1577]

.LIS = VLAN = Broadcast Domain

.LIS내의communication은ATM ATP server를이용해host간에end-to-end direct VCC설정가능

.LIS간의communication은Router를통해

.Routing between LISs

.one-armed router

.NHRP


































































































































LIS 1

LIS 2


Physical View

Logical View

ARP server

Router
LIS 1
LIS 2



Netmanias Confidential

16

NHRP address resolution














LIS X














LIS Y













LIS Z





























NHS 1
NHS 2















Dst IP ATM addr{Y.1, BBB}...{Z.1, CCC}
NHR cache

Dst IP  next hop
{Z.1, NHS2}
...

Routing table




PVC(NHC2)

Dst IP ATM addr{Z.1, CCC}...
NHR cache





{Y.1, BBB}
...
{Z.3, CCC}

NHR cache


UNI signaling for establishing SVC (AAA-CCC)


Data transfer

.

.
.

.
.

.
.

.

IP =X.1
ATM =AAA

IP=Z.1ATM=CCC
NHRP (Next Hop Resolution Protocol)NHS (Next Hop Resolution Server)=Router + NHRP
MPOA = LANE + Route server + NHRP



Netmanias Confidential

17

CSR(Cell Switch Router): Motivation

CIOA







LIS X





Router1

Router 2




X.1

Z.1


LIS Y


LIS Z







ATM cloud

CSR






LIS X
CSR 1

CSR 2





X.1

Z.1



LIS Y


LIS Z


ATM cloud















AAL



Default-VC
LIS내의host간통신은direct VCC을통해가능하지만, LISs간통신을위해서는반드시router를거쳐야한다.
; X.1.VC x .R1(reassemble .IP forwarding .segmentation) .VC y .
R2(reassemble .IP forwarding .segmentation) .VC z .Z.1
Bottleneck .Router between subnets

LISs간통신시에두모드가능(1) Layer 3 forwarding : hop-by-hop IP level packet routing(2) Layer 2 switching: ATM Bypass-pipe라는cut-through path를설정; X.1.ATM Bypass-pipe.Z.1ATM Bypass-pipe(=multiple VCs) : X.1 .dedicated-VC a .CSR1:switching .dedicated-VC b .CSR2:switching .dedicated-VC c.Z.1)

Dedicated
-VC

IP

ATM

Default-VC

AAL



IP

ATM




AAL


IP

ATM



Default
-VC

Dedicated-VC
Dedicated
-VC


AAL

IP

ATM



AAL



VC x

IP

ATM
VC y

AAL



IP

ATM



AAL


IP

ATM


VC z

AAL


IP
ATM



Bypass-pipe
Objective of CSR: Interconnect LISs without packet-by-packet Layer 3 forwarding



Netmanias Confidential

18
CSR Architecture overview
.CSR(Cell Switch Router)

.conventional hop-by-hop IP packet forwarding + cell switching function(이로인해서로다른LIS간통신시에도cut-though path가설정됨)


.Default-VC

.end host/edge router와CSR간또는한쌍의CSRs간에통신채널로모든트래픽(routing protocols-OSPF/BGP, data traffic, etc.)이전달되는a general purpose VC.

.Default-VC로들어오는모든ATM셀은assembled .IP forwarding (hop-by-hop packet forwarding)


.Dedicated-VC

.특정IP packet flow(예를들어, {src.IP address, dest.IP address})가검출/감지되면그flow에할당되는VC

.두CSRs간에(즉, 한subnet내에서)만의미가있다.

.두개의dedicated-VC은cut-through packet forwarding path를형성하며이때CSR은VPI/VCI값을이용해스위칭한다.

.이때dest.IP address와VPI/VCI간의mapping을위해FANP을이용


.Bypass-pipe

.특정IP packet flow에대한CSRs간dedicated-VC이모이면ATM Bypass-pipe 생성됨.










LIS X

CSR 1

CSR 2





X.1

Z.1



LIS Y

LIS Z


ATM cloud















AAL



Default-VC

Dedicated
-VC

IP

ATM

Default-VC

AAL



IP
ATM




AAL


IP

ATM



Default
-VC

Dedicated-VC
Dedicated
-VC


AAL

IP

ATM



Bypass-pipe



Netmanias Confidential

19




























ATM Bypass-pipe
.Bypass-pipe

.host-to-host: S3.CSR1 .CSR2 .D3

.router-to-host: R2 .CSR1 .CSR2 .D3

.host-to-router: S3 .CSR1 .CSR2 .R4

.router-to-router: R2 .CSR1 .CSR2 .R4










LIS X





s3

D3



LIS Y


LIS Z


ATM cloud














CSR 2

CSR 1
Network Reference Model

R2
D2

s2

R4



Netmanias Confidential

20
An example of IP datagram transmission mechanism

.CSR에Cell도착..check VPI/VCI.Lookup table(incoming interface, VPI, VCI?)


.Yes.switching(outgoing interface, VPI,VCI, CSR2까지간다)
.No.reassemble.IP packet(normal IP routing) .segmentation.해당default VC







LIS X

CSR 1

CSR 2





X.1
Z.1



LIS Y

LIS Z


ATM cloud















AAL



Default
-VC


Dedicated
-VC

IP

ATM

Default-VC

AAL




IP

ATM




AAL


IP

ATM


Default
-VC

Dedicated-VC
Dedicated
-VC


AAL

IP

ATM




Bypass-pipe



Netmanias Confidential

21
NHRP-based internetworking architecture와CSR-based architecture

.공통점: 서로다른LISs간에direct ATM level interconnectivity(cut-through path)를제공

.차이점



NHRP








LIS X






IP level routing: OSPF, BGP, IS-IS protocols / IP packet forwarding
(host Z.1의ATM address를얻기위한IP-ARP 즉, NHRP 수행시
ATM network의egress point(ATM addr. of Z.1)를찾을때)
ATM routing: P-NNI (egress point로의an direct ATM VCC 설정시)

NHS 2




X.1

Z.1


LIS Y


LIS Z






VCC

ATM cloud

IP

AAL

ATM

IP
AAL

ATM
NHS 1

Hierarchical routing
IP level routing: Z.1으로IP packet forwarding을위한routing
inter-subnet level path를결정
ATM routing: adjacent nodes(CSR, or ATM attached host/router)간에ATM VCC설정을위한
intra-subset level path를결정

CSR







LIS X




X.1

Z.1


LIS Y


LIS Z

ATM cloud















CSR 2

CSR 1

CSR망구조의경우ATM routing은ATM cloud전체에대해수행되지않고각subnet에서만다른subnet과독립적으로수행되면
되므로ATM routing 을위해요구되는정보량이적다.
CSR망구조의경우end-to-end path는반드시각subnet 경계의router(CSR)를거치도록잡히므로
NHRP로얻은end-to-end ATM path가더optimal하다.



Netmanias Confidential

22

Triggers for Cut-through path
.Topology-driven path establishment

.CSR에새로운forwarding entry가생성될때이route에대한dedicated-VC을설정(cut-through path 설정절차를시작한다)한다.

.Aggregated packet flow

.{ingress edge router, dest.prefix}

.{ingress edge router, egress edge router}

.{*, dest.prefix}, {*, egress edge router}


.Tag switching과유사


.Traffic-driven path establishment [FANPv1.0]

.CSR에packet이들어오면CSR이이packet flow에대해cut-through path(Dedicated-VC)을설정해줄것인가를결정


.Request-driven path establishment

.CSR이RSVP resource reservation request를받으면설정






Netmanias Confidential

23


Interoperation with standard ATM network platform(individual subnet에서dedicated-VC를할당하는3가지방법)

(1) VP-based이웃하는CSRs을VP로연결하고a dedicated-VC이요구될때an unused VC을할당
CSR 1

CSR 2

LIS
















a VP/ a pair of CSRs

(2) PVC-based
(picking up one from a bunch of PVCs)
initialization phase에서
이웃하는CSRs간에PVCs를할당받고
a dedicated-VC이요구될때
이들중하나를할당
1) pick up a PVC
2) FANP(flow-VCID-PVC)
3) dedicated-VC설정

CSR 1

CSR 2


LIS
















PVC-set



...


(3) SVC-based(on-demand SVC setup)a dedicated-VC이요구될때마다ATM signaling을통해SVC를설정해서이를할당1) ATM ARP2) SVC setup3) FANP(flow-VCID-SVC)4) dedicated-VC설정-dedicated-VC setup중에IP datagram을default-VC을통해hop-by-hop forwarding할수도있다.
CSR 1

CSR 2


LIS















SVC



ATM signaling

a dedicated-VC

a dedicated-VC
a dedicated-VC




Netmanias Confidential

24

FANP (Flow Attribute Notification Protocol)



LIS X

CSR 1

CSR 2




X.1
Z.1


LIS Y


LIS Z


















OFFER
{VCID, FLOWID, RIT}



PROPOSE(on dedicated-VC){VCID, src.IP, target IP}

PROPOSE ACK
{VCID}

READY{VCID, FLOWID}

READY
{VCID, FLOWID}


READY
{VCID, FLOWID}

.VCID
negotiation
(notification)

.FLOWID
negotiation
(notification)

.FLOWID
refresh

PROPOSE message가온VC이
flow에대한dedicated-VC이다.

VCID     dedicated-VC
I/F   VPI   VCI
1a1     5      10

VCID   dedicated-VCI/F   VPI   VCI1a1     3      15
Target IP: CSR2의IP addressFLOWID: flow의src.IP address와flow의dest.IP addressRIT: READY message의refresh interval

Dedicated-VC for the flow

FLOWID       VCID
src IP/destIP       1

FLOWID       VCID
src IP/destIP       1

Flow(FLOWID=srcIP/destIP)의
packet은VPI/VCI=3/15로보낸다

Flow(FLOWID=srcIP/destIP)의packet은VPI/VCI=5/10으로온다.
.Dedicated-VC선택

.FLOWIDremoval


“ I’m going to send you traffic
for flow x on the VC with VCID 1”



Netmanias Confidential

25

IP Switching

.CSR ~ Toshiba (CSR, FANP: rfc2098, 2129)

.IP switching~ Ipsilon (GSMP, IFMP: rfc1953, 1954, 1987, 2297)

.Tag switching ~ Cisco (TSR, TDP: rfc2105)

.ARIS(Aggregate Route-based IP Switching) ~ IBM

.MPLS(MultiProtocol Label Switching)



1995 IpsilonRFC2297: \"Ipsilon\'s General Switch Management Protocol Specification Version 2.0\", Mar 1998 RFC1953: \"Ipsilon Flow Management Protocol Specification for IPv4 Version 1.0\" , May 1996 RFC1954: \"Transmission of Flow Labelled IPv4 on ATM Data Links Ipsilon Version 1.0\", May 1996 RFC1987: \"Ipsilon\'s General Switch Management Protocol Specification Version 1.1\" , Aug 1996 LSR(Label Switched Router) = IPS(IP Switch)LDP(Label Distribution Protocol) = IFMP(Ipsilon Flow Management Protocol)


Netmanias Confidential

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IP switching overview

.ATM control plane을없애고IP + label binding protocol(IFMP)을이용해IP packet을ATM switch상에서forwarding

.First one or a few packets:

.default VC(no signaling required, well known VPI/VCI)

.Default VC .IPS(reassembled .pkt-by-pkt forwarding .



segmented) .Default VC
.Flow detection

.flow classification (type1/2)

.setup Cut-though path for the flow (IFMP, GSMP)

.data VC .ISP(switching) .data VC


.IFMP(rfc1953): Ipsilon Flow Management Protocol

.GSMP(rfc1987): General Switch Management Protocol



switch

Flow classification and control

IP
ATM
ARP

MARS
NHRP

PNNI

Q.2931

ATM H/W
IP routing and address resolution
ATM signalingand routing
IP over standard ATM



IP

ATM H/W
IFMP

IP switching


GSMP

IFMP

IP routingforwarding
GSMP









Default VC
Data VC

Default VC

Data VC




IFMP
IFMP

Switchcontroller
IP Switch architecture



Netmanias Confidential

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IP switching operation
Initial path
.IP packets are forwarded hop-by-hop using a default VC.
ATM cells are reassembled in IP packets at each hop.
IP switch controller makes a flow classification decision.

Controller labels a selected flow
.IP switch controller sends an IFMP message to upstream
node to use a new VC for the selected flow.
.use a Traffic for the selected flow begins to flow on the
new VC.
Upstream flow is labeled !


ATMFabric
IP switch
controller



Upstreamnode
Downstream
node

ATM cells
VPI/VCI=0/15


.


IP switchcontroller


Downstreamnode

.
{flow=x, VPI/VCI=3/57}


Upstream
node

.ATM cells
VPI/VCI=3/57

ATM
Fabric



Netmanias Confidential

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IP switching operation (continued)

ATM
Fabric

IP switchcontroller


Downstream
node

.ATM cells
VPI/VCI=2/22

Downstream node also labels flow
.Downstream node also sends an IFMP request for a new VC.
.IP switch sends traffic for that flow to the downstream node
on the new VC. Downstream flow is labeled !


.{flow=x, VPI/VCI=2/22}

ATM cellsVPI/VCI=3/57
Upstreamnode



Netmanias Confidential

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IP switching operation (continued)


ATM
Fabric

IP switch
controller



Downstream
node

.ATM cellsVPI/VCI=2/22
Flows at ATM fabric speed
.Incoming labeled flow switched through to outgoing labeled flow.
(Cut-through operation completed for flow-oriented traffic.)
Switch maintains switching table.

Upstreamnode
.ATM cells
VPI/VCI=3/57


Data VC
(cut-through switching)

Default VC
(pkt-by-pkt forwarding)





Netmanias Confidential

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Flow Classification
Data VC(cut-through switching)

ATM
Fabric

IP switch
controller



Downstream
node






Upstream
node


Aggressiveflow classification
scalability problem
delay associated with setting up binding

Default VC(pkt-by-pkt forwarding)
Data VC
(cut-through switching)


ATMFabric
IP switch
controller


Downstream
node




flow classification
대부분의flow가
packet-by-packet forwarding (S/W)

Default VC
(pkt-by-pkt forwarding)



Upstream
node









Classification !


Netmanias Confidential

31

Switching flow classification

.Flows consist of multiple packets that share, for example, the same source and destination address, type of service, protocol.

.Flow type

.type 1: a port-pair flow type ~ pkts with the same {src IP addr, dest IP addr, src TCP/UDP port, dest TCP/UDP port}  (well-known port number~ port 20: TCP ftp, 80: TCP http)

.type 2: a host-pair flow type ~ pkts with the same {src IP addr, dest IP addr}


.Flow detection

.X/Y

.TCP


.Long-term flows are ideal for cut-through switching.

.Short-term transactions are ideal for datagram forwarding.

.Flow oriented traffic:

.ftp, http, NFS, multimedia audio/video


.Short-lived traffic:

.DNS, NTP, SMTP, POP, SNMP












Classification



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32



IP switching network architecture
.ATM host, Edge router도IP switching에참여


(if IFMP runs on ATM host, Edge router)
.IP switches can directly interconnect hosts


.standard ATM network을통한IP switches간의연결

.PVP(Permanent Virtual Path)사용해야

.CSR처럼PVC, SVC를사용못한다.

.IP switch는VCI를label로사용하므로두IP switch사이의링크에서VCI값이바뀌면(translation) 안된다.












Edgedevice
IP
Switch

IP
Switch

LAN















Fast
Ethernet

ATM host



IFMP
IFMP

IFMP



IPSwitch
IP
Switch

Standard ATM network


PVP



VPI: ATM switching에사용(VP switching)
VCI: label for IP switching

5.3 /2.10
2.10/7.8
3.8
7.8

1.8

3.8/1.2

1.2

5.3

2.10


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33
IP Switching Summary

.Traffic(flow, data)-driven model

.label allocation(label binding to a flow, distribution) is initiated by the arrival of traffic on that flow


.ATM switch(general switch) + IFMP, GSMP = IP switch

.switch controller

.S/W = conventional router(routing, forwarding) + flow detection + label distribution

.aggressive flow classification.all packets are switched



.scalability problem + delay associated with setting up binding
.Advantages

.SVC setup없이packet 전송via default VC

.data VC

.fine granularity (layer4, layer3)


.Disadvantages (or Concern)

.scalability






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Tag Switching

.CSR ~ Toshiba (CSR, FANP: rfc2098, 2129)

.IP switching ~ Ipsilon (GSMP, IFMP: rfc1953, 1954, 1987, 2297)

.Tag switching ~ Cisco (TSR, TDP: rfc2105)

.ARIS(Aggregate Route-based IP Switching) ~ IBM

.MPLS(MultiProtocol Label Switching)



CiscoRFC2105 : \"Cisco Systems\' Tag Switching Architecture Overview\" , Feb 1997 LSR(Label Switched Router) = TSR(Tag Switch Router)LDP(Label Distribution Protocol) = TDP (Tag Distribution Protocol)


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Tag switching

.Tag Switching Operation:

.routes are mapped to tags. This is called a tag biding {address prefix, Tag}

.Tag bindings are distributed among TSR and stored a Tag Information Base(TIB) in the switch.

.Packets/cells are marked with appropriate tag and forwarded based on the contents of the tag.


.Tag can be:

.VPI/VCI field of an ATM cell, DLCI of a Frame Relay PDU

.could be a “shim” layer between layer 3 address and MAC address


.Topology-driven























































































































Tag edge router

Tag switch
(ATM switch or Router)





Tag edge router
Tag Switch
Tag Switch Router(TSR)

Objectives-various routing functionality-better scalability-integration of cell-based technologyand frame-based technology


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Concept of Tag Switching






dest.IP    next hop   I/F165.13/16     R2        if0148.12/16     R3        if1...













FIB

dest.IP    next hop   I/F
165.13/16     R2        if0
148.12/16     R3        if1
...


Addressprefix
Outinterface
165.13/16
if0

148.12/16
if1

In
Tag

9

2
...

...

...
Out
Tag

3
1

...

TIB
FIB
dest.IP    next hop   I/F165.13/16     R2        if0148.12/16     R3        if1...

FIB

R1
R2

R3



165.13/16

data
165.13/16

data

148.12/16
data

148.12/16
data






















R1

R2
R3
dest.IP    next hop   I/F165.13/16     R2        if0148.12/16     R3        if1...

Address
prefix

Outinterface
165.13/16

if0

113.12/16

if1
In
Tag

3

2
...

...
...

Out
Tag

4
9
...
TIB

FIB
Conventional Router
(IP packet forwarding)

Tag Switching Router
(label swapping)

if0

if1
if0

if1

148.12/16
data

4
165.13/16

data

9
165.13/16
data
3

148.12/16
data

1





OSPF
IS-IS
BGP


OSPFIS-ISBGP
.Packet forwarding rate.

.Packet forwarding rate.


TDP
FIB: Forwarding Information Base
TIB: Tag Information Base



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37

Destination-based routing
.Local tag binding

.Distribute the local binding

.Remote tag binding





Netmanias Confidential

38



.Local tag binding





























if1
if0

if2

if1

if2
if0

if1

if2
if0

if2

if0
if1
if1

if2

if0
dest.IP      next hop   I/F
165.13/16       B           if1
...


Addressprefix
165.13/16

Out
I/F

if1

InTag
10

next
hop

B
TIB

FIB


A
B
C

D

E
Out
Tag

(  )
dest.IP      next hop   I/F
165.13/16       E           if1
...


Address
prefix

165.13/16

OutI/F
if1

In
Tag

6
next
hop

E

TIB
FIB

Out
Tag

(  )

dest.IP      next hop   I/F165.13/16       D           if2...

Address
prefix

165.13/16
Out
I/F

if2

In
Tag

17
next
hop

D

TIB
FIB


Out
Tag

(  )
dest.IP      next hop   I/F165.13/16       E           if1...

Address
prefix

165.13/16

OutI/F
if0

InTag
5

next
hop

E

TIB
FIB


Out
Tag

(  )
dest.IP      next hop   I/F
165.13/16      local      if0
...


Address
prefix

165.13/16
OutI/F
if0

In
Tag

8
next
hop

E
TIB

FIB


Out
Tag

-
165.13 network

.Local tag binding
-entry in FIB.entry in TIB
-{inTag, address prefix}
-a route에a tag할당
-independent binding
.distribute the tag binding information
(TDP)
.remote tag binding
-tag binding{Tag, address prefix}를받은TSR는
-TIB에address prefix에대한entry가있는가?
-이entry의next hop이tag binding을보낸
TSR인가?
-TIB의outTag필드에tag값을기록

Two route to 165.13 networkA .B .EC .D .E(by routing protocol)
.






















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39
.Distribute and .remote binding

if1

if0
Address
prefix

165.13/16
Out
I/F

if1

In
Tag

10
next
hop

B

TIB A
Out
Tag

6

Address
prefix

165.13/16
Out
I/F

if1

InTag
6

nexthop
E

TIB B

Out
Tag

8
Address
prefix

165.13/16

OutI/F
if2

In
Tag

17

nexthop
D

TIB C

OutTag
5

Addressprefix
165.13/16

Out
I/F

if0

InTag
5

next
hop

E
TIB D

Out
Tag

8

Addressprefix
165.13/16

Out
I/F

if0
In
Tag

8
next
hop

E

TIB E

OutTag
-

.Local tag binding
-entry in FIB.entry in TIB
-{inTag, address prefix}
.distribute the tag binding information
(TDP: Tag Distribution Protocol)
.remote tag binding
-tag binding{Tag, address prefix}를받은TSR는
-TIB에address prefix에대한entry가있는가?
-이entry의next hop이tag binding을보낸
TSR인가?
-TIB의outTag필드에tag값을기록











if1
if0

if2

if2

if0
if1

if2

if0
if2

if1
if0

A

B

C
D

E

165.133 network





{8, 165.133}

{6, 165.133}

{10, 165.133}

{8, 165.133}




































{5, 165.133}







{5, 165.133}










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40
Tag switching operation























































































































In
Tag

Address
prefix

Outinterface
Out
Tag

X

168.82
if1

4

X

165.13
if0

17

...

...

...
...


17

17


165.13.58.6
data


165.13.58.6

data

168.82.58.6

data


Edge에서는packet의IP address를이용해forwarding
Core에서는packet에장착된Tag를이용해switching

5
In
Tag

Address
prefix

Out
interface

Out
Tag

4
168.82

if1

9

17
165.13

if2

5
...

...

...

...


5

165.13.58.6

data


8

InTag
Address
prefix

Out
interface

Out
Tag

9
168.82

if1

2
5

165.13

if0

8
...

...

...

...



8
165.13.58.6

data


In
Tag

Addressprefix
Out
interface

Out
Tag

2
168.82

if0

X

8
165.13

if0

X

...

...
...

...



165.13.58.6

data

165.13 network



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Improving Routing Scalability via a Hierarchy of routing knowledge

.Internet routing architecture

.models the Internet as a collection of routing domains

.intradomain routing: OSPF, RIP, EIGRP

.interdomain routing: BGP

.scalable routing


.Transit routing domain

.every router must maintain in its forwarding table all the routes provided by the interdomain routing, regardless of whether this is a interior router or border router, in order to forward the transit traffic through the domain.

.Interior router in a transit routing domain are basically just transferring packets from one border router to another, so it seems somewhat wasteful for them to have to maintain complete routing tables for all routes in the Internet


.Tag Switching gives a solution for this problem.

.Interior routers store only the routing information they really need-just enough to get packets to the right border router

.Border routers have full routing information






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Within a Routing Domain















































Routing Domain A

Routing Domain B

Routing Domain C

border router
T

X

Y

W
V

Z















interior router















P
Q

.Routing domain A의모든TSR은intradomain routing protocol(OSPF, RIP)에참여하여RD A의모든border router를destination으로하여FIB를작성하고, 이를토대로destination-based routing방식과동일하게TIB를작성한다.



if0
if0

if1

if0

if0

destination
W

In
Tag

-

-
Q

Out I/F
next hop

if0, X

if0,W
Out
Tag

10
2
destination

W

In
Tag

10

2
Q

Out I/F
next hop

if1, Y

if0, P
Out
Tag

12

7

destination
W

InTag
12
...

...

Out I/F
next hop

if0, W

...
Out
Tag

17

...

destination
W

In
Tag

17


...
Out I/F
next hop

if0, W
...
Out
Tag

-

...

TSR T

TSR X
TSR Y

TSR W

destination

Q
In
Tag

7

...

...
Out I/F
next hop

if0, Q
...
Out
Tag

5

...

destination

Q
In
Tag

5


...

Out I/Fnext hop
if0, Q

...

Out
Tag

-
...

TSR P
TSR Q












OSPF

TDP



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Border Router

.서로다른Routing domain과연결되어있는모든TSR은interdomain routing protocol(BGP)에참여하여얻은모든routes에대해tag 할당, tag biding하여TIB를작성한다.

.이때, next hop은border router가된다.(provided by BGP)





















































Routing Domain A

Routing Domain B
Routing Domain C

border router

T

X
Y

W
V
Z















interior router















P

Q

if0
if0

if1
if0

if0





BGP






TDP

destination

165.13
In
Tag

3
...
...

Out I/F
next hop

if0, T

...

OutTag
2

...
TSR T

destination
165.13

In
Tag

6


...
Out I/F
next hop

if0, K
...
Out
Tag

10

...

TSR W

TSR Y
destination

W
In
Tag

-
-

Q

Out I/F
next hop

if0, X
if0,W

OutTag
10
2

TSR T

5

165.13

if0,W
2

destination
W

InTag
10

2

Q

Out I/Fnext hop
if1, Y

if0, P
OutTag
12

7

TSR X

...

...
...

...
destination

W
In
Tag

12

...

...
Out I/F
next hop

if0, W
...
Out
Tag

17

...

...

...
...

...
destination

W
In
Tag

17


...

Out I/Fnext hop
if0, W

...
OutTag
-

...

TSR W

2

165.13
if0, Z

6


Netmanias Confidential

44

TS

.Border TSR의FIB와TIB에는intradomain route에대한entry와interdomain route에대한entry가모두존재한다.

.Interior TSR의FIB와TIB에는intradomain에대한entry만존재한다.

.Forwarding scheme: use Tag stack, not a single tag !





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Example













































Routing Domain A
Routing Domain B

Routing Domain C
Addressprefix
165.13

In
Tag

9

...

...
Out I/F
next hop

If0, T
...

Out
Tag

5
...

Address
prefix

165.13
In
Tag

6
...
...

Out I/F
next hop

if0

...

OutTag
8

...
border router

T

X
Y

W

V
Z















Addressprefix
W

InTag
-
5

165.13

Out I/F
next hop

if0, X

if0, W
Out
Tag

10
2

Address
prefix

W
In
Tag

10

...
...

Out I/Fnext hop
if0, Y
...

Out
Tag

12

...

Addressprefix
W

InTag
12

...

...
Out I/F
next hop

if0, W

...
Out
Tag

17
...
Address
prefix

W

In
Tag

17

2
163.13

Out I/Fnext hop
if0, W

if0, Z

OutTag
-

6

TSR T
TSR X

TSR Y
TSR W
TSR V

interior router

165.13

data

5
165.13

data
2

10

165.13
data

2

12
165.13

data
2
17

165.13

data

6

[5] .TSR T: (5 .2), 10부착.[2,10] .TSR X  packet의next hop W, TIB에서destiantion이W인entry를찾는다.Tag을2로swapping하고top tag=10을부가TSR X: (10 .12) .[2,12] .TSR YTSR Y: (12 .17) .[2,17] .TSR WTSR W: 17제거, (2 .6) .[6] .TSR Z           W의TIB에서next hop이W자신으로되어있다. (의미: tag=17로들어온packet의top tagg를pop off!)

5
165.13

data

2
10


swapping
adding

165.13
data
2

17

6



Pop off

swapping
TSR Z



Netmanias Confidential

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Improving Routing Scalability via a Hierarchy of routing knowledge

.To summarize, the use of hierarchy of routing knwledge allows complete isolation of the interior routers within a routing domain from interdomain routing, thus improving the stability and scalability of routing





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47

Tag switching with ATM
.ATM-TSR: TSR의control component + ATM switch H/W



Inport   VPI   VCI

1         10    5

2          3     7

...

Outport  VPI  VCI
3        6       21

8        9       10
...

ATM lookup table


10/5



6/21





Outport 3

Lookup VPI/VCI
Level swapping and switching

ATM routing and signaling
(UNI, PNNI)

Tag Switching
Control Component
(OSPF, BGP, PIM, RSVP,TDP)



교체

ATM cell forwarding
기능은그대로유지



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Carrying Tag

.Tag stack = 1 level tag : VCI field에tag를기록

.216= 64 K tags/port


.Tag stack = 2 level tag : VPI field에first tag


VCI field에second tag 기록
.212= 4096 tags/port


.Predefined VPI/VCI





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VC-explosion
.CSR, IP switching은traffic-driven policy로active flow에대해서만label이할당

.ATM도Call duration 동안만VPI/VCI 할당

.Tag switching

.Topology-driven tag allocation

.allocates one tag per one route in FIB..VC-explosion!

.Solution: VC-merging






































































































































TSR

TSR

































ATM-TSR
































ATM-TSR



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Problem in VC-merging

.“cell-interleave” problem






















TSR A
TSR B
ATM-TSRX
IP pkt

5

cell

7
cell

7

IP pkt

8

cell

7
cell

7

5/7

8/7
cell
3
cell

3

cell

3
cell

3




















TSR A
TSR B

TSR C

IP pkt

5
pkt
7
pkt

7

IP pkt

8
pkt

7

pkt

7

5/7

8/7
pkt

3

pkt

3
pkt
3
pkt

3








서로다른pkt들이서로섞여져서edge router(TSR)에서이셀들을제대로reassemble할수없다.
7/3

Q1) Why does this happen ?
A1) downstream tag allocation !
Q2) In case of TSRs ?
A2) pkt-by-pkt forwarding !










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51

Solution 1: VC-merging




















TSR A

TSR B

ATM-TSR
X

IP pkt
5
cell
7

cell

7

IP pkt

8

cell

7

cell

7

5/7
TIB

8/7

TIB

cell
3
cell
3

cell

3

cell

3

TIB
7/3


Mark of
End of pkt


Mark ofEnd of pkt
...

...



pkt from B
pkt from A
































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Solution 2: On-demand tag allocation(multiple tag allocation per route)




















TSR A

TSR B

ATM-TSR
X

IP pkt

5
cell

7

cell

7
IP pkt

8

cell

4

cell

4

5/7

8/4

cell

3

cell

2
7/3
4/2

...








cell

3

cell

2


























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ARIS

.모든ingress ISR에서각Egress ISR로multipoint-to-point tree(VC)를형성하여egress ISR로가려는traffic은이tree를공유

.Tag switching처럼Topology-driven

.Tag switching에서는FIB내의모든entry에대해tag allocation

.ARIS에서는한Egress ISR에대해하나의label이allocation됨

.ISR(Integrated Switch Router)

.Egress ID(identifier)

.ISR information Base

.RIB(Routing Information Base)

.FIB(Forwarding Information Base)

.VCIB(VC Information Base)






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ARIS vs Tag Switching



























































A

F
G

C

D

E

E

171.69.210

165.13


Edge TSR



Tag Switching(coarse granularity)


























































A

F
G

C

D

E
E

171.69.210

165.13

Egress ISR




ARIS
(coarsest granularity)




Label allocation
per route

Label allocation
per aggregate route



Netmanias Confidential

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ARIS operation



































































destination

171.69.210

...

Next
hop

A

...
Out
label

-

...

In
label

-


FIB  A
Egress
ID

A

...

ISR  A

destination

171.69.210

...

Next
hop

D
...

Out
label

10

...

In
label

-


FIB  F

Egress
ID

A

...

F

G

C

D

E
E

171.69.210

Establish
{17, E-ID=A}

destination

171.69.210

...

Nexthop
A

...

Out
label

17

...

In
label

10


FIB  C
Egress
ID

A

...

destination

171.69.210

...

Nexthop
C

...

Out
label

10

...

In
label

14


FIB  D
Egress
ID

A

...





destination

171.69.210

...

Next
hop

D

...

Out
label

10

...
In
label

14


FIB  E

Egress
ID

A

...





Establish
{10, E-ID=A}

Establish
{10, E-ID=A}


Establish{14, E-ID=A}
Establish
{14, E-ID=A}



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scalability

.VP-merging

.multiple label allocation





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Comparison of label switching technologies

CSR

IP

Tag switching

ARIS

ATM, FR (CO)

ATM

ATM, FR, Ethernet

ATM, FR
Upstream

Downstream

Downstream

Downstream(Egress ISR)
FANP

IFMP

TDP
ARISp

Host-to-host
{src IP addr, dest IPaddr}

Host-to-host
{src IP addr, dest IPaddr}

Destination network
(address prefix)

Egress ISR
(Egress ID)

CSR

Datalink

Initiator

VC setupprotocol
Granularity

No

No

Yes (tag stack)
Yes (Tunnel)

LAN

LAN
WAN, ISP

WAN, ISP

Interconnect LISs
via bypass-pipe


scalability

scalability

Yes

No

No
No

Hierarchy of labels

Area

Objectives
ATM SVC
interworking

Data-driven

Data-driven
Control-driven

Control-driven

Data/Control



VC-merging(single VC/route)
multiple VCs per route

VP-merging(single VP/egress)
multiple VCs per route

scalability

Independent
Independent

Independent
(except explicit route)

Ordered (from Egress)

Binding creation


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58
Conclusion

.Motivations for label switching

.Solutions

.NHRP/MPOA

.Cell Switch Router (Toshiba)

.IP Switching (Ipsilon)

.Tag Switching (Cisco)

.ARIS (IBM)

.Comparisons for label switching approaches


.MPLS(MultiProtocol Label Switching)

 

 

     
         
     

 

     
     

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