19-InternetworkingOperation

8/6/2019 19-InternetworkingOperation

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Data and ComputerData and Computer

CommunicationsCommunications

Eighth EditionEighth Editionby William Stallingsby William Stallings

Lecture slides by Lawrie BrownLecture slides by Lawrie Brown

Chapter 19Chapter 19 Internetwork OperationInternetwork Operation


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Internetwork OperationInternetwork Operation

She occupied herself with studying a map on the

opposite wall because she knew she would have

to change trains at some point. Tottenham Court

Road must be that point, an interchange fromthe black line to the red. This train would take

her there, was bearing her there rapidly now,

and at the station she would follow the signs, forsigns there must be, to the Central Line going

westward King Solomon's Carpet, Barbara

Vine (Ruth Rendell)


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Internetwork OperationInternetwork Operation

consider mechanisms for handling growth inconsider mechanisms for handling growth in

network trafficnetwork traffic

from lowfrom low--volume text based terminal/emailvolume text based terminal/email

to high volume multito high volume multi--media web/voice/videomedia web/voice/video

historically IP nets gave besthistorically IP nets gave best--effort datagrameffort datagram

delivery to all servicesdelivery to all services

now want variety of QoS in IP networksnow want variety of QoS in IP networks explore some new network services / functionsexplore some new network services / functions


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MulticastingMulticasting

sending packet to addresses referring tosending packet to addresses referring to

group of hosts on one or more networksgroup of hosts on one or more networks

multimedia broadcastmultimedia broadcast teleconferencingteleconferencing

databasedatabase

distributed computingdistributed computing

real time workgroupsreal time workgroups

have design issues in addressing / routinghave design issues in addressing / routing


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LANMulticastLANMulticast

LAN multicast is easyLAN multicast is easy

send to IEEE 802 multicast MAC addresssend to IEEE 802 multicast MAC address

since broadcast all stations will see packetsince broadcast all stations will see packet those in multicast group will accept itthose in multicast group will accept it

only single copy of packet is neededonly single copy of packet is needed

but much harder in internetworkbut much harder in internetwork


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ExampleExample

ConfigConfig


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Broadcast / Multiple Unicast /Broadcast / Multiple Unicast /

Multicast

Multicast

could broadcast packet to each networkcould broadcast packet to each network

if server does not know members of groupif server does not know members of group

requires 13 packetsrequires 13 packets

could send multiple unicast packetscould send multiple unicast packets

to each net with members in multicast groupto each net with members in multicast group


or use true multicastor use true multicast which send single packets over any linkwhich send single packets over any link

duplicating as needed to reach dest netsduplicating as needed to reach dest nets



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rue MulticastTrue Multicast

determine least cost path to each networkdetermine least cost path to each network

that has host in groupthat has host in group

results in a spanning treeresults in a spanning tree of just those nets with members in groupof just those nets with members in group

transmit single packet along spanning treetransmit single packet along spanning tree

routers replicate packets at branch pointsrouters replicate packets at branch pointsof spanning treeof spanning tree


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Multicast ExampleMulticast Example


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Requirements forRequirements for

Multicasting

Multicasting

router may have to forward more than onerouter may have to forward more than onecopy of packetcopy of packet

need convention to identify multicastneed convention to identify multicastaddresses (IPv4 Class D or IPv6 prefix)addresses (IPv4 Class D or IPv6 prefix)

nodes translate between IP multicastnodes translate between IP multicastaddresses and list of networks containingaddresses and list of networks containing

group membersgroup members router must translate between IP multicastrouter must translate between IP multicast

address and network multicast addressaddress and network multicast address


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Requirements forRequirements for

Multicasting

Multicasting

mechanism required for hosts to join and leavemechanism required for hosts to join and leave

multicast groupmulticast group

routers must exchange inforouters must exchange info

which networks include members of given groupwhich networks include members of given group

sufficient info to work out shortest path to eachsufficient info to work out shortest path to each

networknetwork

routing algorithm to work out shortest pathrouting algorithm to work out shortest path routers must determine routing paths based onrouters must determine routing paths based on

source and destination addressessource and destination addresses


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Spanning Tree from Router CSpanning Tree from Router C

toM

ulticast GrouptoM

ulticast Group


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Internet Group ManagementInternet Group Management

ProtocolProtocol ((IGM

PIGM

P)) RFCRFC 33763376 to exchange multicast group infoto exchange multicast group info

between hosts & routers on a LANbetween hosts & routers on a LAN

hosts send messages to routers to subscribehosts send messages to routers to subscribe toto

and unsubscribe from multicast groupand unsubscribe from multicast group

routers check which multicast groups of interestrouters check which multicast groups of interest

to which hoststo which hosts

IGMP currently version 3IGMP currently version 3


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Operation of IGMPv1 & v2Operation of IGMPv1 & v2

IGMPv1IGMPv1 hosts could join grouphosts could join group

routers used timer to unsubscribe membersrouters used timer to unsubscribe members

IGMPv2IGMPv2 enabled hosts to unsubscribeenabled hosts to unsubscribe

operational model:operational model: receivers have to subscribe to groupsreceivers have to subscribe to groups

sources do not have to subscribesources do not have to subscribe toto groupsgroups

any host can send traffic to any multicast groupany host can send traffic to any multicast group

problems:problems: spamming of multicast groupsspamming of multicast groups

establishment of distribution trees is problematicestablishment of distribution trees is problematic

finding globally unique multicast addresses difficultfinding globally unique multicast addresses difficult


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IGMP v3IGMP v3

addresses weaknesses:addresses weaknesses:

allowsallows hosts to specify list from which theyhosts to specify list from which they

want to receive trafficwant to receive traffic traffic from other hosts blocked at routerstraffic from other hosts blocked at routers

allowsallows hosts to block packets from sourceshosts to block packets from sources

that send unwanted trafficthat send unwanted traffic


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IGMP Message FormatsIGMP Message Formats

Membership Query

Membership Query

sent by multicast routersent by multicast router

three types: general querythree types: general query, g, grouproup--specific query, groupspecific query, group--

andand--source specific querysource specific query


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Membership Query FieldsMembership Query Fields

TypeType

Max Response TimeMax Response Time

ChecksumChecksum

Group AddressGroup Address

S FlagS Flag

QRV (querier's robustness variable)QRV (querier's robustness variable)

QQIC (querier's querier interval code)QQIC (querier's querier interval code) Number of SourcesNumber of Sources

Source addressesSource addresses


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Membership Report

Membership Report


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Group RecordGroup Record


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IGMP OperationIGMP Operation -- JoiningJoining

IGMP hostIGMP host wants towants to make itself known asmake itself known as groupgroupmember to other hosts and routers on LANmember to other hosts and routers on LAN

IGMPv3IGMPv3 cancan signal group membership withsignal group membership with

filtering capabilities with respect to sourcesfiltering capabilities with respect to sources EXCLUDE modeEXCLUDE mode all members except those listedall members except those listed

INCLUDE modeINCLUDE mode only from group members listedonly from group members listed

to join send IGMP membership report messageto join send IGMP membership report message address field multicast address of groupaddress field multicast address of group sent in IP datagramsent in IP datagram

currentcurrent group members receive & learn new membergroup members receive & learn new member

routersrouters listen to all IP multicast addresses to hear alllisten to all IP multicast addresses to hear all

reportsreports


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IGMP OperationIGMP Operation

KeepingL

ists ValidKeepingL

ists Valid routersrouters periodically issue IGMP general queryperiodically issue IGMP general query

messagemessage inin datagram with alldatagram with all--hosts multicast addresshosts multicast address

hostshosts must read such datagramsmust read such datagrams hostshosts respond withrespond with report messagereport message

routerrouter dont know every host in a groupdont know every host in a group needs to know at least one group member still activeneeds to know at least one group member still active

each host in group sets timer with random delayeach host in group sets timer with random delay host hearing another reporthost hearing another report cancelscancels ownown

if timer expires, host sends reportif timer expires, host sends report

onlyonly one member of each groupone member of each group reportsreports to routerto router


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IGMP OperationIGMP Operation -- LeavingLeaving

hosthost leaves groupleaves group by sendingby sending leave groupleave group

message to allmessage to all--routers static multicast addressrouters static multicast address

sends asends a membership report message withmembership report message with EXCLUDEEXCLUDE

optionoption andand null list of source addressesnull list of source addresses

routerrouter determines if have any remaining groupdetermines if have any remaining group

membersmembers usingusing groupgroup--specific query messagespecific query message


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Group Membership with IPv6Group Membership with IPv6

IGMP defined for IPv4IGMP defined for IPv4

usesuses 3232--bit addressesbit addresses

IPv6 internets need functionalityIPv6 internets need functionality IGMPIGMP functions included in Internetfunctions included in Internet

Control Message ProtocolControl Message Protocol v 6v 6 (ICMPv6)(ICMPv6)

ICMPv6 has functionality of ICMPv4 & IGMPICMPv6 has functionality of ICMPv4 & IGMP ICMPv6 includes groupICMPv6 includes group--membership querymembership query

and groupand group--membership report messagemembership report message


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Routing ProtocolsRouting Protocols

routers receive and forward packetsrouters receive and forward packets

make decisions based on knowledge ofmake decisions based on knowledge of

topology and traffic/delay conditionstopology and traffic/delay conditions use dynamic routing algorithmuse dynamic routing algorithm

distinguish between:distinguish between:

routing informationrouting information -- about topology & delaysabout topology & delays routing algorithmrouting algorithm -- that makes routingthat makes routing

decisions based on informationdecisions based on information


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Autonomous Systems (AS)Autonomous Systems (AS)

is a group of routers and networksis a group of routers and networks

managed by single organizationmanaged by single organization

which exchange information via a commonwhich exchange information via a commonrouting protocolrouting protocol

form a connected networkform a connected network

at least one path between any pair of nodesat least one path between any pair of nodes except in times of failureexcept in times of failure


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Application of IRP and ERPApplication of IRP and ERP


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Approaches to RoutingApproaches to Routing

DistanceDistance--vectorvector each node (router or host) exchange informationeach node (router or host) exchange information

with neighboring nodeswith neighboring nodes

first generation routing algorithm for ARPANETfirst generation routing algorithm for ARPANET

eg. used byeg. used by Routing Information Protocol (RIP)Routing Information Protocol (RIP)

each node maintains vector of link costs for eacheach node maintains vector of link costs for each

directly attached network and distance and nextdirectly attached network and distance and next--

hop vectors for each destinationhop vectors for each destination requires transmission ofrequires transmission of muchmuch info by routersinfo by routers

distance vector & estimated path costsdistance vector & estimated path costs

changes take longchanges take long time to propagatetime to propagate


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Approaches to RoutingApproaches to Routing

LinkL

ink--statestate designed to overcome drawbacks of distancedesigned to overcome drawbacks of distance--vectorvector

each router determines link cost on each interfaceeach router determines link cost on each interface

advertises set of link costs to all other routers in topologyadvertises set of link costs to all other routers in topology

if link costsif link costs changechange,, router advertisesrouter advertises newnew valuesvalues

eacheach router constructs topology of entire configurationrouter constructs topology of entire configuration

can calculate shortest path to each destcan calculate shortest path to each dest

use to constructuse to construct routing table with first hop to each destrouting table with first hop to each dest

dodo not use distributed routing algorithmnot use distributed routing algorithm, but any suitable, but any suitablealg toalg to determine shortest pathsdetermine shortest paths, eg., eg. Dijkstra's algorithmDijkstra's algorithm

Open Shortest Path First (OSPF) is a linkOpen Shortest Path First (OSPF) is a link--state protocolstate protocol


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What ExteriorRoutingWhat ExteriorRouting

Protocols are notProtocols are not linklink--state and distancestate and distance--vectorvector notnot effective foreffective for

exterior router protocolexterior router protocol

distancedistance--vectorvector assumes routers share common distance metricassumes routers share common distance metric but different ASs may have different priorities & needsbut different ASs may have different priorities & needs

but have no info on ASs visited along routebut have no info on ASs visited along route

linklink--statestate different ASs may use different metrics and havedifferent ASs may use different metrics and have

different restrictionsdifferent restrictions

flooding of link state information to all routersflooding of link state information to all routersunmanageableunmanageable


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ExteriorRouter ProtocolsExteriorRouter Protocols

PathPath--vectorvector alternativealternative pathpath--vectorvectorrouting protocolrouting protocol

provides info about which networks can be reachedprovides info about which networks can be reachedby a given router and ASs crossed to get thereby a given router and ASs crossed to get there

does not includedoes not include distance or cost estimatedistance or cost estimate hence dispenses with concept of routing metricshence dispenses with concept of routing metrics

have list of all ASs visitedhave list of all ASs visited onon a routea route

enables router to perform policy routingenables router to perform policy routing

eg.eg. avoid path to avoid transiting particular ASavoid path to avoid transiting particular AS eg.eg. link speed, capacity, tendency to becomelink speed, capacity, tendency to become

congested, and overall quality of operationcongested, and overall quality of operation, security, security

eg.eg. minimizing number of transit ASsminimizing number of transit ASs


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Border Gateway ProtocolBorder Gateway Protocol

(BGP)(BGP) developed for use with TCP/IP internetsdeveloped for use with TCP/IP internets

is preferred EGP of the Internetis preferred EGP of the Internet

uses messages sent overT

CP connectionuses messages sent overT

CP connection current version is BGPcurrent version is BGP--4 (RFC1771)4 (RFC1771)

functional proceduresfunctional procedures

neighbor acquisitionneighbor acquisition -- when agree to exchange infowhen agree to exchange info

neighbor reachabilityneighbor reachability -- to maintain relationshipto maintain relationship

network reachabilitynetwork reachability -- to update database of routesto update database of routes


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BGPBGP

MessagesMessages

OpenOpen

UpdateUpdate

Keep aliveKeep alive

NotificationNotification


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Message TypesMessage Types --

Open & KeepA

liveOpen & KeepA

live router makes TCP connection to neighborrouter makes TCP connection to neighbor

Open messageOpen message

sent by connection initiatorsent by connection initiator

includes proposed hold timeincludes proposed hold time

receiver uses minimum of own/sent hold timereceiver uses minimum of own/sent hold time

max time between Keepalive and/or Updatemax time between Keepalive and/or Update Keep Alive messageKeep Alive message

To tell other routers that this router is still hereTo tell other routers that this router is still here


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Message TypesMessage Types -- UpdateUpdate

Update message conveys two info types:Update message conveys two info types:

Info about single routes through internetInfo about single routes through internet

List of routes being withdrawnList of routes being withdrawn info on a route uses 3 fields:info on a route uses 3 fields:

Network LayerReachability Information (NLRI)Network LayerReachability Information (NLRI)

Total Path Attributes LengthTotal Path Attributes Length

Path AttributesPath Attributes

withdraw route identified by dest IP addresswithdraw route identified by dest IP address


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Message TypesMessage Types -- UpdateUpdate

OriginOrigin -- IGP or EGPIGP or EGP

AS_PathAS_Path -- list of AS traversedlist of AS traversed

Next_hopNext_hop -- IP address of border routerIP address of border router

Multi_Exit_DiscMulti_Exit_Disc -- info on routers internal to ASinfo on routers internal to AS

Local_prefLocal_pref -- inform routers in AS of route prefinform routers in AS of route pref

Atomic_Aggregate, AggregatorAtomic_Aggregate, Aggregator -- implementimplementroute aggregation to reduce amount of inforoute aggregation to reduce amount of info


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AS_Path and Next_Hop UseAS_Path and Next_Hop Use

AS_PathAS_Path

used to implement routing policiesused to implement routing policies

eg. to avoid a particular AS, security, performance,eg. to avoid a particular AS, security, performance,

quality, number of AS crossedquality, number of AS crossed

Next_HopNext_Hop

only a few routers implement BGPonly a few routers implement BGP

responsible for informing outside routers ofresponsible for informing outside routers ofroutes to other networks in ASroutes to other networks in AS


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Notification MessageNotification Message

sent when some error condition detected:sent when some error condition detected:

Message header errorMessage header error

Open message errorOpen message errorUpdate message errorUpdate message error

Hold time expiredHold time expired

Finite state machine errorFinite state machine error

CeaseCease


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BGP Routing InformationBGP Routing Information

Ex

changeEx

changewithin AS a router builds topology picturewithin AS a router builds topology picture

using IGPusing IGP

router issues Update message to otherrouter issues Update message to otherrouters outside AS using BGProuters outside AS using BGP

these routers exchange info with otherthese routers exchange info with other

routers in other ASrouters in other AS

AS_Path field used to prevent loopsAS_Path field used to prevent loops

routers must then decide best routesrouters must then decide best routes


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Open Shortest Path FirstOpen Shortest Path First

(RFC2328)(RFC2328) IGP of InternetIGP of Internet

replaced Routing Information Protocol (RIP)replaced Routing Information Protocol (RIP)

uses Link State Routing Algorithmuses Link State Routing Algorithm each router keeps list of state of local links to networkeach router keeps list of state of local links to network

transmits update state infotransmits update state info

little traffic as messages are small and not sent oftenlittle traffic as messages are small and not sent often

uses least cost based on user cost metricuses least cost based on user cost metric

topology stored as directed graphtopology stored as directed graph vertices or nodes (router, transit or stub network)vertices or nodes (router, transit or stub network)

edges (between routers or router to network)edges (between routers or router to network)


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ExampleExample

OSPF ASOSPF AS


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DirectedDirected

Graph ofGraph ofASAS


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SPF TreeSPF Tree

forfor

Router 6Router 6


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Integrates ServicesIntegrates Services

A

rchitectureA

rchitecture changes in traffic demands require varietychanges in traffic demands require variety

of quality of serviceof quality of service

eg. internet phone, multimedia, multicasteg. internet phone, multimedia, multicast new functionality required in routersnew functionality required in routers

new means of requesting QoSnew means of requesting QoS

IETF developing a suite ofIETF developing a suite of IntegratedIntegratedServices Architecture (ISA)Services Architecture (ISA) standardsstandards

RFC 1633 defines overall view of ISARFC 1633 defines overall view of ISA


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Internet Traffic CategoriesInternet Traffic Categories

elastic trafficelastic traffic

can cope with wide changes in delay and/orcan cope with wide changes in delay and/orthroughputthroughput

traditional TCP/IP traffictraditional TCP/IP traffic

eg. FTP, email, telnet, SNMP, HTTPeg. FTP, email, telnet, SNMP, HTTP

different sensitivity to throughput, delay,different sensitivity to throughput, delay,congestioncongestion

inelastic trafficinelastic traffic

does not easily adapt to variationsdoes not easily adapt to variations


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Inelastic Traffic RequirementsInelastic Traffic Requirements

throughputthroughput

delaydelay

jitterjitter packet losspacket loss

need preferential treatment for some trafficneed preferential treatment for some traffictypestypes

require elastic traffic to be supportedrequire elastic traffic to be supported


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ISAApproachISAApproach

IP nets control congestion byIP nets control congestion by

routing algorithmsrouting algorithms

packet discardpacket discard

ISA provides enhancements to traditional IPISA provides enhancements to traditional IP

in ISA associate each packet with a flowin ISA associate each packet with a flow

ISA functions:ISA functions:

admission controladmission control routing algorithmrouting algorithm

queuing disciplinequeuing discipline

discard policydiscard policy


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ISAISA in Routerin Router


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ISAServicesISAServices

GuaranteedGuaranteed assured data rateassured data rate

upper bound on queuing delayupper bound on queuing delay

no queuing lossno queuing loss Controlled loadControlled load

approximates best effort behavior on unloaded netapproximates best effort behavior on unloaded net

no specific upper bound on queuing delayno specific upper bound on queuing delay

very high delivery successvery high delivery success Best EffortBest Effort

traditional IP servicetraditional IP service


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Token Bucket SchemeToken Bucket Scheme


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Queuing DisciplineQueuing Discipline

traditionally FIFOtraditionally FIFO

no special treatment for high priority flow packetsno special treatment for high priority flow packets

large packet can hold up smaller packetslarge packet can hold up smaller packets

greedy connection can crowd out less greedygreedy connection can crowd out less greedyconnectionconnection

need some form of fair queuingneed some form of fair queuing

multiple queues used on each output portmultiple queues used on each output port

packet is placed in queue for its flowpacket is placed in queue for its flow

round robin servicing of queuesround robin servicing of queues

can have weighted fair queuingcan have weighted fair queuing


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FIFO and Fair QueueFIFO and Fair Queue


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Resource Reservation: RSVPResource Reservation: RSVP

RFC 2205RFC 2205

unicast applications can reserve resources inunicast applications can reserve resources in

routers to meet QoSrouters to meet QoS

if router can not meet request, application informedif router can not meet request, application informed

multicast more demanding, but may be reducedmulticast more demanding, but may be reduced

some members of group may not require deliverysome members of group may not require delivery

from particular source over given timefrom particular source over given time

some group members may only be able to handle asome group members may only be able to handle a

portion of the transmissionportion of the transmission

reservation means routers can decide in advance ifreservation means routers can decide in advance if

can meet requirementscan meet requirements


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Soft StateSoft State

have different resource reservation needshave different resource reservation needs

to traditional connectionto traditional connection--oriented networksoriented networks

must dynamically changemust dynamically change use concept of Soft Stateuse concept of Soft State

set of state info in router that expires unlessset of state info in router that expires unless

refreshedrefreshed

applications must periodically renewapplications must periodically renew

requests during transmissionrequests during transmission


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RSVP CharacteristicsRSVP Characteristics

unicast and multicastunicast and multicast

simplexsimplex

receiver initiated reservationreceiver initiated reservationmaintain soft state in the internetmaintain soft state in the internet

provide different reservation stylesprovide different reservation styles

transparent operation through nontransparent operation through non--RSVPRSVProutersrouters

support for IPv4 and IPv6support for IPv4 and IPv6


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Differentiated ServicesDifferentiated Services

simple, easily implemented, low overhead tool tosimple, easily implemented, low overhead tool to

support a range of differentiated network servicessupport a range of differentiated network services

IP Packets labeled for differing QoS using existingIP Packets labeled for differing QoS using existing

IPv4 Type of Service or IPv6 DS fieldIPv4 Type of Service or IPv6 DS field

have service level agreement establishedhave service level agreement established

between provider and customer prior to use of DSbetween provider and customer prior to use of DS

have built in aggregationhave built in aggregation implemented by queuing and forwarding based onimplemented by queuing and forwarding based on

DS octetDS octet

most widely used QoS mechanism todaymost widely used QoS mechanism today


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DSServicesDSServices

is defined within a DS domainis defined within a DS domain a contiguous portion of internet over which consistenta contiguous portion of internet over which consistent

set of DS policies are administeredset of DS policies are administered

typically under control of one organizationtypically under control of one organization defined by service level agreements (SLA)defined by service level agreements (SLA)

specify service received for classes of packetsspecify service received for classes of packets

once established customer submits packets withonce established customer submits packets withDS marked indicating classDS marked indicating class service provider ensures agreed QoS within domainservice provider ensures agreed QoS within domain

if transit other domains, provider chooses closest QoSif transit other domains, provider chooses closest QoS


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SLA ParametersSLA Parameters

detailed service performance such as:detailed service performance such as:

expected throughputexpected throughput

drop probabilitydrop probability latencylatency

constraints on ingress and egress pointsconstraints on ingress and egress points

traffic profilestraffic profiles disposition of traffic in excess of profiledisposition of traffic in excess of profile


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Example ServicesExample Services

level Alevel A -- low latencylow latency

level Blevel B -- low losslow loss

level Clevel C -- 90% of traffic < 50ms latency90% of traffic < 50ms latency level Dlevel D -- 95% in profile traffic delivered95% in profile traffic delivered

level Elevel E -- allotted twice bandwidth of level Fallotted twice bandwidth of level F

level Flevel F -- with drop precedence X haswith drop precedence X hashigher probability of delivery than that of Yhigher probability of delivery than that of Y


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DS FieldDS Field


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DS FieldDS Field -- DS CodepointDS Codepoint

6 bit field in IPv4 & IPv6 header6 bit field in IPv4 & IPv6 header

3 pools of code points3 pools of code points

xxxxx0xxxxx0 -- assignment as standardsassignment as standards 000000000000 -- default best effortdefault best effort

xxx000xxx000 -- IPv4 precedence compatibilityIPv4 precedence compatibility

xxxx11xxxx11 -- experimental or local useexperimental or local use

xxxx01xxxx01 -- experimental or local but may beexperimental or local but may beallocated for standards in futureallocated for standards in future


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IPv4 Precedence ServiceIPv4 Precedence Service

IPv4 TOS field included subfieldsIPv4 TOS field included subfields

precedence (3 bit)precedence (3 bit) -- datagram urgency/prioritydatagram urgency/priority

TOS(4 bit)TOS(4 bit) -- guidance on selecting next hopguidance on selecting next hop

can respond withcan respond with

route selectionroute selection -- smaller queue, has prioritysmaller queue, has priority

network servicenetwork service -- supports precedencesupports precedence

queuing disciplinequeuing discipline -- support precedencesupport precedenceordered queueing & discard lower precedenceordered queueing & discard lower precedence


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DS Configuration andDS Configuration and

OperationOperation

within domain, interpretation of DS codewithin domain, interpretation of DS code

points is uniformpoints is uniform

interior nodesinterior nodes implement simple mechanismsimplement simple mechanisms

perper--hop behavior (PHB) on all routershop behavior (PHB) on all routers

boundary nodesboundary nodes

have PHB & more sophisticated mechanismshave PHB & more sophisticated mechanisms

hence most of complexityhence most of complexity


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DS Traffic ConditionerDS Traffic Conditioner


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PerHop BehaviorPerHop Behavior

Expedited ForwardingExpedited Forwarding specific PHBs definedspecific PHBs defined

expedited forwarding (EF) PHB (RFC 3246)expedited forwarding (EF) PHB (RFC 3246) lowlow--loss, lowloss, low--delay, lowdelay, low--jitter, assured bandwidth,jitter, assured bandwidth,

endend--toto--end service through DS domainsend service through DS domains simulates a pointsimulates a point--toto--point connection or leased linepoint connection or leased line

difficultdifficult inin internet or packetinternet or packet--switching networkswitching network queuesqueues onon node/routernode/router rresult in loss, delays, and jitteresult in loss, delays, and jitter

unless internet grossly oversizedunless internet grossly oversized,, carecare neededneeded ininhandling premium servicehandling premium service traffictraffic

EF PHB intent is to use empty/short queues toEF PHB intent is to use empty/short queues tominimise delay, jitter & packet loss.minimise delay, jitter & packet loss.

E dit d F diE dit d F di


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Expedited ForwardingExpedited Forwarding

RequirementsRequirements EF PHB designed to configure nodes so trafficEF PHB designed to configure nodes so traffic

aggregate has minimum departure rateaggregate has minimum departure rate

border routers condition traffic aggregate (viaborder routers condition traffic aggregate (via

policing / shaping) so arrival rate is less thanpolicing / shaping) so arrival rate is less thanminimum departure rate for nodesminimum departure rate for nodes

interior nodes treat trafficinterior nodes treat traffic so noso no queuing effectsqueuing effects

no specificno specific queuing policy set for interior nodesqueuing policy set for interior nodes

note a simple priority scheme can achievenote a simple priority scheme can achieve thisthis EF traffic given absolute priorityEF traffic given absolute priority

EF trafficEF traffic must notmust not overwhelm interior nodeoverwhelm interior node

but packet flows for other PHB traffic disruptedbut packet flows for other PHB traffic disrupted


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Assured Forwarding PHBAssured Forwarding PHB

provide service superior to bestprovide service superior to best--efforteffort

without needingwithout needing reservation of resourcesreservation of resources orordetailed flow discriminationdetailed flow discrimination

based on explicit allocationbased on explicit allocation users offered choice of classes of serviceusers offered choice of classes of service

traffic monitored at boundary node, marked in/outtraffic monitored at boundary node, marked in/out

inside network, no separation of traffic from differentinside network, no separation of traffic from different

users or classesusers or classes whenwhen congested,congested, drop out packets before in packetsdrop out packets before in packets

different users will see different levels of servicedifferent users will see different levels of service

advantage is simplicityadvantage is simplicity


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AFAF PHBPHB RFC 2597RFC 2597

four AF classes / traffic profiles are definedfour AF classes / traffic profiles are defined

within each class, packets markedwithin each class, packets marked with twith threehree

drop precedence valuesdrop precedence values

in congestion determines relative importancein congestion determines relative importance

simpler, moresimpler, more flexibleflexible than resource reservationthan resource reservation

within interior DS node, traffic fromwithin interior DS node, traffic from differentdifferent

classes isclasses is treated separatelytreated separately different resources (buffer space, data rate)different resources (buffer space, data rate)

hence forwarding assurance depends onhence forwarding assurance depends on

resources, current load & drop precedenceresources, current load & drop precedence


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Service Level AgreementsService Level Agreements

is a contract between network provideris a contract between network provider

and customer for aspects of serviceand customer for aspects of service

typically includes:typically includes: description of nature of servicedescription of nature of service

expected performance level of serviceexpected performance level of service

process for monitoring & reporting serviceprocess for monitoring & reporting service

levellevel

similar to frame relay / ATM SLAssimilar to frame relay / ATM SLAs

but more difficult to realizebut more difficult to realize


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Service Level AgreementsService Level Agreements


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IP Performance MetricsIP Performance Metrics

IP Performance Metrics working group isIP Performance Metrics working group is

developing a standard set of metricsdeveloping a standard set of metrics

on quality, performance, reliabilityon quality, performance, reliability

to provide common understandingto provide common understanding

3 stages of metrics3 stages of metrics

singleton metricsingleton metric -- elementary / atomic quantityelementary / atomic quantity

sample metricsample metric -- taken over time periodtaken over time period

statistical metricstatistical metric -- derived from samplederived from sample

active or passive measurementactive or passive measurement


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IP Performance MetricsIP Performance Metrics

Me tric Na me

One -Way De lay

o nd -T rip De lay

One -Way Loss

One -Way Loss Pattern (distance / pe riod )

Packe t De lay a riation

Conn ectivity

lk TransferCapa city


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SummarySummary

reviewed various internetwork services &reviewed various internetwork services &

functions to support varying servicesfunctions to support varying services

multicastingmulticasting routing protocolsrouting protocols

integrated services architectureintegrated services architecture

differentiated servicesdifferentiated services service level agreementsservice level agreements

IP performance metricsIP performance metrics

19-InternetworkingOperation

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