Data Communications,Data Networks,computer communications,multiplexing,spread spectrum,protocol architecture,data link protocols,signal encoding techniques,transmission media,asynchronous transfer mode,routing,cellular networks,lan,wan,man,high speed lans,internet protocols

1. Data and ComputerData and Computer
CommunicationsCommunications
Eighth EditionEighth Edition
by William Stallingsby William Stallings
Lecture slides by Lawrie BrownLecture slides by Lawrie Brown
Chapter 19 – Internetwork OperationChapter 19 – Internetwork Operation

2. 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
from the 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, for signs there must be, to the Central
Line going westward —King Solomon's Carpet,
Barbara Vine (Ruth Rendell)

3. Internetwork OperationInternetwork Operation
 consider mechanisms for handling growth inconsider mechanisms for handling growth in
network trafficnetwork traffic

from low-volume text based terminal/emailfrom low-volume text based terminal/email

to high volume multi-media web/voice/videoto high volume multi-media web/voice/video
 historically IP nets gave best-effort datagramhistorically IP nets gave best-effort 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

4. 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 “broadcast”multimedia “broadcast”

teleconferencingteleconferencing

databasedatabase

distributed computingdistributed computing

real time workgroupsreal time workgroups
 have design issues in addressing / routinghave design issues in addressing / routing

5. LAN MulticastLAN Multicast
 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

6. ExampleExample
ConfigConfig

7. Broadcast / Multiple Unicast /Broadcast / Multiple Unicast /
MulticastMulticast
 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

requires 11 packetsrequires 11 packets
 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

requires 8 packetsrequires 8 packets

8. True 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 points
of spanning treeof spanning tree

9. Multicast ExampleMulticast Example

10. Requirements forRequirements for
MulticastingMulticasting
 router may have to forward more than onerouter may have to forward more than one
copy of packetcopy of packet
 need convention to identify multicastneed convention to identify multicast
addresses (IPv4 Class D or IPv6 prefix)addresses (IPv4 Class D or IPv6 prefix)
 nodes translate between IP multicastnodes translate between IP multicast
addresses 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

11. Requirements forRequirements for
MulticastingMulticasting
 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

12. Spanning Tree from Router CSpanning Tree from Router C
to Multicast Groupto Multicast Group

13. Internet Group ManagementInternet Group Management
ProtocolProtocol ((IGMPIGMP))
 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

14. 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

15. 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

16. IGMP Message FormatsIGMP Message Formats
Membership QueryMembership Query
 sent by multicast routersent by multicast router
 three types: general querythree types: general query, g, group-specific query, group-roup-specific query, group-
and-source specific queryand-source specific query

17. 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

18. IGMP Message FormatsIGMP Message Formats
Membership ReportMembership Report

19. IGMP Message FormatsIGMP Message Formats
Group RecordGroup Record

20. IGMP Operation - JoiningIGMP Operation - Joining
 IGMP hostIGMP host wants towants to make itself known asmake itself known as groupgroup
member 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 listed– all members except those listed

INCLUDE modeINCLUDE mode – only from group members listed– only 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

21. IGMP Operation –IGMP Operation –
Keeping Lists ValidKeeping Lists Valid
 routersrouters periodically issue IGMP general queryperiodically issue IGMP general query
messagemessage

inin datagram with all-hosts multicast addressdatagram with all-hosts multicast address

hostshosts must read such datagramsmust read such datagrams

hostshosts respond withrespond with report messagereport message
 routerrouter don’t know every host in a groupdon’t 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

22. IGMP Operation - LeavingIGMP Operation - Leaving
 hosthost leaves groupleaves group by sendingby sending leave groupleave group
message to all-routers static multicast addressmessage to all-routers 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 group-specific query messagegroup-specific query message

23. Group Membership with IPv6Group Membership with IPv6
 IGMP defined for IPv4IGMP defined for IPv4

usesuses 32-bit addresses32-bit 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 group-membershipICMPv6 includes group-membership
query and group-membership reportquery and group-membership report
messagemessage

24. 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 information - about topology & delaysrouting information - about topology & delays

routing algorithm - that makes routingrouting algorithm - that makes routing
decisions based on informationdecisions based on information

25. 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 common
routing 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

26. Interior Router Protocol &Interior Router Protocol &
Exterior Routing ProtocolExterior Routing Protocol
 interior router protocol (IRP)interior router protocol (IRP)

passes routing information between routers within ASpasses routing information between routers within AS

can be tailored to specific applicationscan be tailored to specific applications

needs detailed model of network to functionneeds detailed model of network to function
 may have more than one AS in internetmay have more than one AS in internet

routing algorithms & tables may differ between themrouting algorithms & tables may differ between them
 routers need info on networks outside own ASrouters need info on networks outside own AS
 use an exterior router protocol (ERP) for thisuse an exterior router protocol (ERP) for this

supports summary information on AS reachabilitysupports summary information on AS reachability

27. Application of IRP and ERPApplication of IRP and ERP

28. Approaches to Routing –Approaches to Routing –
Distance-vectorDistance-vector
 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 foreach node maintains vector of link costs for
each directly attached network and distance andeach directly attached network and distance and
next-hop vectors for each destinationnext-hop 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

29. Approaches to Routing –Approaches to Routing –
Link-stateLink-state
 designed to overcome drawbacks of distance-vectordesigned to overcome drawbacks of distance-vector
 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 suitable
alg toalg to determine shortest pathsdetermine shortest paths, eg., eg. Dijkstra's algorithmDijkstra's algorithm
 Open Shortest Path First (OSPF) is a link-state protocolOpen Shortest Path First (OSPF) is a link-state protocol

30. What Exterior RoutingWhat Exterior Routing
Protocols are notProtocols are not
 link-state and distance-vectorlink-state and distance-vector notnot effective foreffective for
exterior router protocolexterior router protocol
 distance-vectordistance-vector

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 AS’s visited along routebut have no info on AS’s visited along route
 link-statelink-state

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 routers
unmanageableunmanageable

31. Exterior Router Protocols –Exterior Router Protocols –
Path-vectorPath-vector
 alternativealternative path-vectorpath-vector routing protocolrouting protocol

provides info about which networks can be reachedprovides info about which networks can be reached
by 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

32. 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 over TCP connectionuses messages sent over TCP connection
 current version is BGP-4 (RFC1771)current version is BGP-4 (RFC1771)
 functional proceduresfunctional procedures

neighbor acquisition - when agree to exchange infoneighbor acquisition - when agree to exchange info

neighbor reachability - to maintain relationshipneighbor reachability - to maintain relationship

network reachability - to update database of routesnetwork reachability - to update database of routes

33. BGPBGP
MessagesMessages
 OpenOpen
 UpdateUpdate
 Keep aliveKeep alive
 NotificationNotification

34. Message Types -Message Types -
Open & KeepAliveOpen & KeepAlive
 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

35. Message Types - UpdateMessage Types - Update
 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 Layer Reachability Information (NLRI)Network Layer Reachability 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

36. Message Types - UpdateMessage Types - Update
 Origin - IGP or EGPOrigin - IGP or EGP
 AS_Path - list of AS traversedAS_Path - list of AS traversed
 Next_hop - IP address of border routerNext_hop - IP address of border router
 Multi_Exit_Disc - info on routers internal to ASMulti_Exit_Disc - info on routers internal to AS
 Local_pref - inform routers in AS of route prefLocal_pref - inform routers in AS of route pref
 Atomic_Aggregate, Aggregator - implementAtomic_Aggregate, Aggregator - implement
route aggregation to reduce amount of inforoute aggregation to reduce amount of info

37. 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 of
routes to other networks in ASroutes to other networks in AS

38. Notification MessageNotification Message
 sent when some error condition detected:sent when some error condition detected:
 Message header errorMessage header error
 Open message errorOpen message error
 Update message errorUpdate message error
 Hold time expiredHold time expired
 Finite state machine errorFinite state machine error
 CeaseCease

39. BGP Routing InformationBGP Routing Information
ExchangeExchange
 within 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 other
routers 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

40. 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)

41. ExampleExample
OSPF ASOSPF AS

42. DirectedDirected
Graph ofGraph of
ASAS

43. SPF TreeSPF Tree
forfor
Router 6Router 6

44. Integrates ServicesIntegrates Services
ArchitectureArchitecture
 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 of IntegratedIETF developing a suite of Integrated
Services Architecture (ISA) standardsServices Architecture (ISA) standards
 RFC 1633 defines overall view of ISARFC 1633 defines overall view of ISA

45. Internet Traffic CategoriesInternet Traffic Categories
 elastic trafficelastic traffic

can cope with wide changes in delay and/orcan cope with wide changes in delay and/or
throughputthroughput

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

46. Inelastic Traffic RequirementsInelastic Traffic Requirements
 throughputthroughput
 delaydelay
 jitterjitter
 packet losspacket loss
 need preferential treatment for some trafficneed preferential treatment for some traffic
typestypes
 require elastic traffic to be supportedrequire elastic traffic to be supported

47. ISA ApproachISA Approach
 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

48. ISAISA in Routerin Router

49. ISA ServicesISA Services
 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

50. Token Bucket SchemeToken Bucket Scheme

51. 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 greedy
connectionconnection
 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

52. FIFO and Fair QueueFIFO and Fair Queue

53. 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

54. Soft StateSoft State
 have different resource reservation needshave different resource reservation needs
to traditional connection-oriented networksto traditional connection-oriented 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

55. RSVP CharacteristicsRSVP Characteristics
 unicast and multicastunicast and multicast
 simplexsimplex
 receiver initiated reservationreceiver initiated reservation
 maintain soft state in the internetmaintain soft state in the internet
 provide different reservation stylesprovide different reservation styles
 transparent operation through non-RSVPtransparent operation through non-RSVP
routersrouters
 support for IPv4 and IPv6support for IPv4 and IPv6

56. 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

57. DS DomainsDS Domains

58. DS ServicesDS Services
 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 with
DS 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

59. 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

60. Example ServicesExample Services
 level A - low latencylevel A - low latency
 level B - low losslevel B - low loss
 level C - 90% of traffic < 50ms latencylevel C - 90% of traffic < 50ms latency
 level D - 95% in profile traffic deliveredlevel D - 95% in profile traffic delivered
 level E - allotted twice bandwidth of level Flevel E - allotted twice bandwidth of level F
 level F - with drop precedence X haslevel F - with drop precedence X has
higher probability of delivery than that of Yhigher probability of delivery than that of Y

61. DS FieldDS Field

62. DS Field - DS CodepointDS Field - DS Codepoint
 6 bit field in IPv4 & IPv6 header6 bit field in IPv4 & IPv6 header
 3 pools of code points3 pools of code points

xxxxx0 - assignment as standardsxxxxx0 - assignment as standards
• 000000 - default best effort000000 - default best effort
• xxx000 - IPv4 precedence compatibilityxxx000 - IPv4 precedence compatibility

xxxx11 - experimental or local usexxxx11 - experimental or local use

xxxx01 - experimental or local but may bexxxx01 - experimental or local but may be
allocated for standards in futureallocated for standards in future

63. IPv4 Precedence ServiceIPv4 Precedence Service
 IPv4 TOS field included subfieldsIPv4 TOS field included subfields

precedence (3 bit) - datagram urgency/priorityprecedence (3 bit) - datagram urgency/priority

TOS(4 bit) - guidance on selecting next hopTOS(4 bit) - guidance on selecting next hop
 can respond withcan respond with

route selection - smaller queue, has priorityroute selection - smaller queue, has priority

network service - supports precedencenetwork service - supports precedence

queuing discipline - support precedencequeuing discipline - support precedence
ordered queueing & discard lower precedenceordered queueing & discard lower precedence

64. 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

per-hop behavior (PHB) on all routersper-hop behavior (PHB) on all routers
 boundary nodesboundary nodes

have PHB & more sophisticated mechanismshave PHB & more sophisticated mechanisms

hence most of complexityhence most of complexity

65. DS Traffic ConditionerDS Traffic Conditioner

66. Per Hop Behavior –Per Hop Behavior –
Expedited ForwardingExpedited Forwarding
 specific PHBs definedspecific PHBs defined
 expedited forwarding (EF) PHB (RFC 3246)expedited forwarding (EF) PHB (RFC 3246)

low-loss, low-delay, low-jitter, assured bandwidth,low-loss, low-delay, low-jitter, assured bandwidth,
end-to-end service through DS domainsend-to-end service through DS domains

simulates a point-to-point connection or leased linesimulates a point-to-point connection or leased line
 difficultdifficult inin internet or packet-switching networkinternet or packet-switching 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 inin
handling premium servicehandling premium service traffictraffic
 EF PHB intent is to use empty/short queues toEF PHB intent is to use empty/short queues to
minimise delay, jitter & packet loss.minimise delay, jitter & packet loss.

67. 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 than
minimum 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

68. Assured Forwarding PHBAssured Forwarding PHB
 provide service superior to best-effortprovide service superior to best-effort
 without needingwithout needing reservation of resourcesreservation of resources oror
detailed 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

69. 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

70. 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 SLA’ssimilar to frame relay / ATM SLA’s
 but more difficult to realizebut more difficult to realize

71. Service Level AgreementsService Level Agreements

72. 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 metric - elementary / atomic quantitysingleton metric - elementary / atomic quantity

sample metric - taken over time periodsample metric - taken over time period

statistical metric - derived from samplestatistical metric - derived from sample
 active or passive measurementactive or passive measurement

73. IP Performance MetricsIP Performance Metrics
Metric Name
One-Way Delay
Round-Trip Delay
One-Way Loss
One-Way Loss Pattern (distance / period)
Packet Delay Variation
Connectivity
Bulk Transfer Capacity

74. 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