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CHAPTER 5Advanced Networking Technologies

C. Develder and M. Pickavet

Technologies 2

Content

1. Traffic Engineering

2. Failure Recovery

3. Multicast

4. Ethernet

5. IPv6

Technologies 3

How to route the traffic (or more general: engineer the traffic)?

Now: Shortest path (hop count) routing!

Alternatives:

- Constraint based routing (use other metrics)- Load balancing (use different routes)- MPLS (Multi Protocol Label Switching) as

supportingtechnology

Traffic Engineering

Technologies 4

QoS routing: taking certain constraints into account(bandwidth, delay, cost, …)

CONSTRAINT BASED ROUTING (could be very complex) (additive [hop count, delay], multiplicative [loss rate], concave constraints [bandwidth])

How to distribute “constraint” information? (e.g. BW on links)

Add information on link state during OSPF (Q-OSPF)

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Routing table gets much more complex!

low BWfiber link

high BWsatellite link

low delay

High BW

Very useful for both DiffServ and IntServ!

How to find the route with the required QoS?

Technologies 5

Load balancing: distribute traffic more evenly over the network:

- equal cost multipath (use of hash function)- use of MPLS

Shortest path problem: overload certain links

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Load balancing

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Technologies 6e.g. use for DiffServ

IP payloadIP headerMPLS header

MPLS header (32 bit): Label (20 bit): MPLS labelExp (3 bit): experimental useS (1 bit): stacking bitTTL (8 bit): time to live

3

5

5 4

Label InformationBase (LIB)

Link in Label in Link out Label out

1 5 1 4

2 3 1 5

… … … …

Label SwitchedRouter (LSR)

LSR

IN 1

IN 2 OUT 2

OUT 1

local significance

MPLS: Multi Protocol Label Switching

Technologies 7

Routing <> Label Switching

1

2

3

45

6

7

8

AB

189.123.42.34/16

189.123.0.0 2

189.123.0.0 6

189.123.0.0 8189.123.0.0 B

189.123.0.0 7

B

m

kd

w

kg

g: m 5

m: k 3

k: d 4

d: w 8

w: k B

B k

B m

B d

B w

B k

IP router

IP/MPLS Label Switched Router (LSR)

B g

Technologies 8

MPLS: Path set-up (LSP)

A B

C

D

Y

RSVP-TE

Z

X

W

PATH Lab_Req Y PATH Lab_Req Y

PATH Lab_Req Y

Need label forDestination Y

(LABEL_REQUESTobject in

PATH msg)

PA

TH

Lab

_Req

Y

RESV Lab 300

RE

SV

Lab

100

RESV Lab 100

RESV Lab

200

Respond with alabel (receive)(LABEL objectin RESV msg)

200100

100200300100

100200

100

300

LabelInformation

Base

Label SwitchedRouter

Y: to B Y: to C

Y: to Y

Technologies 11

MPLS: support of TE

A B

C

D

Z

X

W MPLS Label

IP header

200100

300100100200

Y50150

150450 450100

300

100 200

100

50

150

450100

Technologies 12

157.193.0.0145.12.0.0

A BF

C

DE

OUT 1

OUT 2

network gateway interface145.12.0.0 B OUT 1

… … …

network gateway interface label145.12.0.0 C OUT 2 5

… … …

5

34

3

LSP

MPLS tunnel (LSP) set-up via explicit routing: during path set-up an explicit path is used

(not the OSPF shortest, but e.g. a constraint based path with lowest delay)

145.12.134.3

MPLS: Example MPLS “tunnel”

Technologies 13

MPLS Virtual Private Network between three company locations

157.193.0.0145.12.0.0

153.145.0.0

Public Internet(MPLS capable)

LSP

MPLS could be combined with DiffServ to provide QoS (the 3 Exp bits are used toindicate the PHB)

easy end-to-endencryption forsecurity

MPLS: VPN example

Technologies 14

Content

1. Traffic Engineering

2. Failure Recovery

3. Multicast

4. Ethernet

5. IPv6

Technologies 15

A B C

E D

Router C: Routing Table

Dest. Nexthop

Interface

A B BCB Direct BCD Direct CDE D CD

knowledge ofnetwork topology

Dijkstra: shortest paths

Router C: Link-State Database

Link Cost SequenceAB 1 A,5AE 1 A,6BD 1 B,6BC 1 B,7CD 1 D,7DE 1 D,6

[AB,BD,BC]

[BD,CD,DE]

[AE,DE]

[AB,AE]

incominglink statepackets

normal operation

Failure Recovery: OSPF based

Technologies 16

Router C: Routing Table

Dest. Nexthop

Interface

A B BCB Direct BCD Direct CDE B BC

knowledge ofnetwork topology

Dijkstra: shortest paths

Router C: Link-State Database

Link Cost SequenceAB 1 A,5AE 1 A,6BD 1 B,6BC 1 B,7CD 1 D,7

[AB,BD,BC]

[BD,CD]

[AE]

[AB,AE]

incominglink statepackets

A B C

E D

Link ED notadvertised

recovery

this may take 50 to 100 seconds

Failure Recovery: OSPF based

Technologies 17

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copy traffic on backup LSP

take traffic frombackup LSP

if primary LSP fails

Set up back-up LSP between edge routersCopy incoming traffic on primary and back-up LSP (1+1 protection)Select traffic from back-up LSP if primary LSP not available VERY FAST (single decision at receiving end = egress router)

Note: all traffic between the two edge routers may be protected with the same back-up LSP

ingressrouter

egressrouter

primaryLSP

backupLSP

Failure Recovery: MPLS based

Technologies 18

MPLS: failure recovery

A B

C

D

Z

X

W MPLS Label

IP header

200100

300100100200

Y50150

150450 450100

300

100 200

100

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450100

Technologies 19

Content

1. Traffic Engineering

2. Failure Recovery

3. Multicast

4. Ethernet

5. IPv6

Technologies 20

Multicast: multiple unicast

A source is sending the same information to a number of receivers (e.g. video distribution)

Multiple unicast flows or single multicast flow

157.193.122.12

157.193.129.15

157.193.84.54

157.193.13.58

157.193.245.136

157.193.10.1

Technologies 21

Multicast: single multicast tree

Multiple unicast flows or single multicast flow

connection oriented!- requires state in the network- requires signaling- requires special routing protocols

157.193.122.12

157.193.129.15

157.193.84.54

157.193.13.58

157.193.245.136

157.193.10.1157.193.122.12

157.193.129.15

157.193.84.54

157.193.13.58

157.193.245.136

157.193.10.1

226.17.30.197

Class D multicast address( multicast group)

Who belongs to multicast group?

How to become member of the multicast group?

How to set up the multicast tree?

Technologies 22

IGMPInternet Group Management Protocol

(used in a single (sub)network)

Multicast architecture

Internet

MULTICAST ROUTINGDVMRP

Distance Vector Multicast Routing ProtocolPIM

Protocol Independent Multicast(used in a wide area: intradomain)

also interdomain

Technologies 23

Internet Group Management Protocol (IGMP)IGMP messages:

message type sent by purposemembership query : general router ask attached hosts joined multicast groupsmembership query : specific router ask attached hosts specific joined multicast groupmembership report host report host wants to join or is joined to given multicast groupleave group host report leaving multicast group

ERInternet

226.17.30.197 226.17.30.197

226.17.30.197

226.17.32.156

226.17.30.197

226.17.44.23

226.17.44.23

226.17.44.23

226.17.44.23

226.17.32.156

optional! ( soft state)

query

report

Edge Router has to know the multicast groups

where local hostsare subscribed

Technologies 24

Service model of multicast

Service model: - local join of multicast group using IGMP- access router will take care of receiving

multicast group packets (for its local hosts)(use of multicast routing protocol)

- receiver driven joining of a group- senders do not know the receivers- all group members can be sender

Note: no coordination of the choice of a class D address for a multicast group( multiple groups may eventually use the same class D address!)Solution: “source filtering”, as in IGMP v3

Remaining question: How to interconnect the edge routers?Use of multicast routing protocols

Technologies 25

Multicast routing: group shared tree

How to build up the routing tree between edge routers?first approach: multicast group shared tree

Note: all group members use the same (bidirectional) tree

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Technologies 26

Multicast routing: group shared tree

How to build up the routing group shared tree?Use of a rendezvous point (center based approach)

Note: choice of rendezvous point is difficult

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Technologies 27

Multicast routing: source based tree

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Second approach: multiple source based treesNote: trees will be different and in general unidirectional

Technologies 28

Multicast routing: source based tree

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Note: prune messages from edge routers that have no hosts belonging to the multicast group

How to build up a source based tree?Use of a Reverse Path Forwarding (RPF)

An incoming multicast packet is forwarded in a router on all of its outgoing links (except the one on which the packet was received) only if the packet arrived on the link that is on its own shortest pathback to the sender

Technologies 29

Multicast routing: source based tree

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Prune messages sent from edge routers that have no hosts belonging to the multicast group(“pruned” routers will not forward packets from the multicast group)

Technologies 30

Examples of multicast routing protocols

Protocol Independent Multicast (PIM)Two different scenarios: dense mode and sparse mode

dense mode (DM): large number of users RPF approachsparse mode (SM): few users central approachbidirectional (BIDIR): variant of SM central approach

Distance Vector Multicast Routing Protocol (DVMRP)

source based treesreverse path forwarding, pruning and grafting

Multicast Open Shortest Path First (MOSPF)Core Based Tree (CBT)

Technologies 31

Content

1. Traffic Engineering

2. Failure Recovery

3. Multicast

4. Ethernet

5. IPv6

Technologies 33

X

1 2 3

4

1 2 3

4A B C

D

1 2 3

4

12

3

Y

Send frame from X to YSend frame back from Y to XFill in switch table

Ethernet: Self learning

Ethernet Switch

X 1

Y 3

X 1 X 4X 4

Y 1Y 4

Technologies 35

X

1 2 3

4

1 2 3

4A B

D1

2

Send frame from X to Y

Ethernet: switched loops

Y

Formation of loopsMultiple copies received by terminals

X 1

X 4

X 3

X 1

X 2

X 1

X 4

Technologies 36

with multiple paths, cycles result - switches may multiply and forward frame forever

for increased reliability, desirable to have redundant, alternative paths from source to dest

solution: organize switches in a spanning tree by disabling subset of interfaces

Spanning Tree Protocol (STP)

Technologies 37

Spanning Tree Protocol (STP)

IEEE 802.1D: Spanning Tree Protocol (STP)STP forms a spanning tree where interfaces are blocked to avoid loops in the network

Switches communicate using 2 types of BPDU’s (Bridge Protocol Data Units):- Configuration BPDU’s (at start-up)- Topology Change Notification BPDU’s and their acknowledgements (during operation)

The spanning tree is built automatically STP will also result in a higher reliability

Technologies 38

Spanning Tree Protocol (STP)

Configuration procedure:Step 1: all ports in blocking modeStep 2: choose a root switch Step 3: minimum spanning tree algorithm calculated in a distributed way using the Port Path Costs (cf. Kruskal)

Step 4: ports will change to forwarding mode based on spanning tree

How to choose the root switch?Based on (lowest) Bridge IDBridge ID format:

Bridge priority (2 bytes) MAC address (6 bytes)

Technologies 40

Spanning Tree Protocol: Example

3 2 6 4

5

1 8

7

root

RP

RP

RP

RPRP RP RP

DP DP

DP

DP

DP

DP

DP

DP

DPBP

BPDP

DPBP

DP

BP

DP BP

BP

RP: Root PortDP: Designated PortBP: Blocked Port

hub

switch

router

Technologies 41

Virtual LAN (VLAN)

(Switched) LAN: Local area network where different hosts are interconnected via switches. They can communicate without limitation.

Virtual LAN (VLAN): Defines a subset of the hosts that are able to communicate within a single VLAN. No layer 2 communication between VLAN’s.

VLAN’s allow more flexible management of the network.

Different VLAN implementations: Untagged (port based)Tagged (802.1Q)

Technologies 42

Virtual LAN (VLAN): port basedA port is mapped on a VLAN (VLAN ID),

(typically manual configuration)Ports will communicate only with other ports having the same VLAN IDLogically separate networks (different IP subnets)

traffic between VLAN’s via external routerNo tags are used

1 2 3 4 5 6 7

Example :VLAN 1: ports 1,2,5,7VLAN 2: ports 3,4,6 VLA

N 1

VLA

N 2

Technologies 43

Virtual LAN (VLAN): port based

Multiple VLAN’s require separate portsInterconnection via IP router

A B C

D

VLAN 1VLAN 2VLAN 3

3 separatelinks

3 separatelinks

IP router

Technologies 44

Virtual LAN (VLAN): tagged

Untagged frame: a frame that does not contain a tag header

(tag not necessary in port based VLAN’s)Tagged frame: a frame that contains a tag header immediately following the Source MAC Address field of the frame. There are two types of tagged frames: VLAN-tagged frames and priority tagged frames:

• VLAN-tagged frame: A tagged frame whose tag header carries both VLAN identification and priority information• priority-tagged frame: A tagged frame whose tag header carries priority information, but carries no VLAN identification information (VID = 0)

VLAN-aware: A property of switches or end stations that recognize and support VLAN-tagged frames

Technologies 45

Virtual LAN (VLAN): tagged

Standard IEEE 802.3 Ethernet Frame format

preamble SFD DA SA T/L data FCS

preamble SFD DA SA T/L data FCSTPID TAG

Userpriority

CFIVLAN

identifier

TPID (Tag Protocol Identifier) = 0x8100

CFI (Canonical Format Indicator) = 0 (for ethernet)

SFD (Start-of-Frame Deliniter)

Extra information is inserted

Technologies 46

Virtual LAN (VLAN): tag based

Multiple VLAN’s can use a single port (due to tagging)Interconnection via IP routerAutomatic configuration possible

A B C

D 1 single

link

1 link or3 separate

links

Technologies 47

Content

1. Traffic Engineering

2. Failure Recovery

3. Multicast

4. Ethernet

5. IPv6

Technologies 48

IPv6

Why a new standard?- exhaust of IP address space- learn from experience with IPv4

- Increase address space from 32 bits to 128 bits- Introduce anycast addresses- Use streamlined 40 bytes header- Introduce the notion of a flow (e.g. audio and video flows)- Support traffic classes (see e.g. DSCP in DiffServ)

Example: send request to any server of a certain type,routing system will deliver only to nearest server

Technologies 49

IPv6

payload length (16)

traffic class (8)version(4) flow label (20)

next header (8) hop limit (8)

source address (128 bit)

destination address (128 bit)

payload

IP address: 8 x 16bit numbers in HEXexample: 3FFE:80B0:0:1:A00:20FF:FEA2:8DBC

Technologies 50

IPv6

4-bitversion

4-bitheaderlength

8-bit ToS 16-bit total length of packet

16-bit identification 3-bit flags 13-bit fragmentoffset

8-bit TTL 8-bit protocol 16-bit header checksum32-bit source IP address

32-bit destination IP address

Options (if any)

Data

payload lengthtraffic classversion flow label

next header hop limit

source address (128 bit)

destination address (128 bit)

payload

No fragmentationNo checksumNo options(but possible via next header)Fixed length of

40 bytes

Ipv6 headernext header = TCP TCP+data

Ipv6 headernext header=routing

routing headernext header=TCP

TCP+data

Ipv6 headernext header=routing

routing headernext header=fragment

fragment headernext header=TCP

TCP+data

Routing header: strict or loose source route (similar to IPv4)Fragment header: similar to IPv4