11-01-K.Steenhaut & J.Tiberghien - VUB 1 Telecommunications Concepts Chapter 4.2 IPv4 and Other Networks

11-01-K.Steenhaut & J.Tiberghien - VUB1

TelecommunicationsConcepts

Chapter 4.2

IPv4 and

Other Networks


Contents• Transmitting IP datagrams

• IP over Local Area Networks• IP over Wide Area Networks

– IP over leased lines– IP over circuit switched networks– IP over packet switched networks

» IP over X25» IP over Frame Relay» IP over ATM» IP and Quality of Service

– MPLS• Conclusions








The Internet Sublayer

IP approachApplication 1 Application 2 Application 3

TCP

Internet Protocolan

yn

etw

ork

UDP


Transmitting IP Datagrams

IProuter

IP router

UnderlyingNetwork

UnderlyingNetwork

IP Datagram

Underlying Network Frame








IP over Ethernet

Application 1 Application 2 Application 3

TCP

Internet Protocol

Ethernet

UDP


Address Resolution Protocol

• Problem :– Mapping of IP and Ethernet addresses

• Solution :– ARP entity broadcasts IP address over

Ethernet

– All hosts compare broadcasted IP address with their own (software defined) IP address

– Identified host answers the ARP broadcast.

– IP datagrams for resolved address are encapsulated in Ethernet frame with Ethernet destination address.


IP over IEEE 802 LANs

4

3

2b

4

3

2b

1 1

IP addresses need to be translated into LAN addresses

2a 2a

802.2 cls


IP over traditional LANs

4

3

4

3

1 1

IP addresses need to be translated into LAN addresses

2a 2a


ReverseAddress Resolution

Protocol• Problem :

– Diskless workstations can not keep their (software defined) IP address.

• Solution :– A configuration server keeps mapping between IP

addresses and corresponding Ethernet addresses.

– At boot time a diskless station broadcasts a RARP frame.

– Configuration server reads source Ethernet address in RARP frame and answers with corresponding IP address.








Directly linked Routers


General Purpose SDH Networks

PABXPABX








IP Networks

Router1.2

1.4

1.3 1.1

2.1

3.3

3.24.1

4.3

4.2

5.2

2.2

2.3

6.1

6.2

5.35.1

7.17.2

6.3


Serial Line Internet Protocol

• Designed in 1984 by Rick Adams (RFC 1055)

• For temporary IP links

• Data Link :

– IP datagrams encapsulated in SLIP frames

– Frame delimited by unique character (11000000)

– Character stuffing within the frame

– No error detection (nor correction !)

• Network Layer : no layer 3 functions

• Many slightly different versions (RFC 1144)

• Essentially obsolete !


Point to Point Protocol

• Designed by the IETF (RFC 1661,RFC 1662,RFC 1663)

• For temporary links (various network protocols)

• Data Link : similar to HDLC or 802.2, but with bytes

– Payload encapsulated in P frames

– Frame delimited by 802.2 flag (01111110)

– Character stuffing within the frame

– Optional error correction with sliding window

• Network Layer : support for different protocols

– Connection management, with authentication

– Network protocol identifier field


Point to Point Protocol

• Multiple protocols over PPP

• Various physical layers under PPP

TCP

IP

PPP

UDP

IPX?

Application,Transport &Network layers

Physical layer

PS

TN

ISD

N

GS

M

Lea

sed

Lin

es

AD

SL

?


P P P Advantages over

SLIP

• CRC on every frame for error detection

• A link control protocol to:

– establish connection

– negotiate options

– close connection

• Specific network control protocols

– e.g. dynamic IP address assignment

– e.g. TCP/IP header compression


IP over ISDN

• Usage :– Temporary interconnections

– Back-up for leased lines

– Additional capacity for overloaded leased lines

• Main problem :IP : Connectionless >< ISDN : Connection oriented

• Solutions :– One call per datagram (fast connection)

– Keep connection for entire billing units

– Keep connection during work-hours








IP over X25

4

3

4

3

1 1

2 2

X25

IP datagramVCNX25 overhead

IP addresses need to be translated into X25 addresses

3 3


IP over X25

• Fast select call : best match between IP and X25

• Virtual circuit between source and destination routers

– Switched : opened and closed when ?

– Permanent : analog to leased line, preferred solution

• Address resolution :

IP address need to be translated into

– X25 address for fast select call or for opening circuit

– VC number for forwarding packet(s)








IP over Frame Relay

4

3

2

4

3

2

1 1

FR

IP datagramVCNFR overhead

IP addresses need to be translated into PVC numbers


IP over Frame Relay

• IP addresses need to be translated into Permanent

Virtual Circuit Numbers.

• Assigning different application flows to PVC’s with

different CIRs can enforce QOS criteria

• Passing the Congestion Notification bits to the

transport layer could be useful but requires special IP

and TCP/UDP implementations








IP over ATM

Ap

plic

ati

on

1

Ap

plic

ati

on

2

Ap

plic

ati

on

3

TCP-UDP

IP

any

net

wo

rk

Ap

plic

ati

on

1

Ap

plic

ati

on

2

Ap

plic

ati

on

3

AT

M

aal

AT

Maal


IP over ATM, but...

• IP is connectionless, – each packet contains destination and origin

addresses.– Broadcasting of messages frequently required

• ATM is connection oriented,– Virtual channels need to be established (and

evt. closed)– each cell contains a Virtual Channel number– ATM addresses are unrelated to IP addresses– No broadcasting

• Connection management required.• Address Translation mechanism required.• Broadcast server required


IP over ATM

4

3

4

3

1 1ATM

IP datagramvcnATM/AAL overhead

AAL


ATM Adaptation Layer

Data encapsulation

pad AAL

pad AAL

Higher layer PDU

ATM header


IP over ATM, solutions

1 . Classical IP over ATM– Initially proposed by IETF

– ARP server translates the addresses

– All addresses stored on one ARP server define one subnet

– Different subnets have to communicate via routers

– Broadcasts have to be generated by IP entity

– Requires modified IP implementation


Classical IP over ATM

Router ARP Server

ATM Network


LAN emulation

Ap

plic

ati

on

1

Ap

plic

ati

on

2

Ap

plic

ati

on

3

TCP-UDP

IP

any

net

wo

rk

AT

MLLC

Ap

plic

ati

on

1

Ap

plic

ati

on

2

Ap

plic

ati

on

3???

???


IP over ATM, solutions

2 . LAN emulation– Proposed by ATM Forum

–Ethernet MAC emulation – Two or three servers:

» Lan Emulation Server registers and translates MAC addresses

» Broadcast and Unknown Server distributes the broadcast and multicast packets

» Lan Emulation Configuration Server keeps ATM addresses of Lan Emulation Servers

– No modifications to IP


LAN Emulation

Router LES,BUS,LECS Servers

ATM Network

Bridge








IP and QOS

• Facts :

– Connectionless IP is unable to guarantee QOS

– Multi-media applications require QOS

• Solutions :

– Provide more than enough capacity between routers

– Force, for specific flows, special routes.

– Use QOS resources of underlying network

» Traditional routing algorithms do not allow differentiation between datagrams with same destination.

» Additional intermediate protocols needed


IP and QOS

• Facts :



• Solutions :







IP and QOS

• Facts :



• Solutions :







IP v4 Header (2)

Source IP Address

Destination IP Address

Options Padding

Header Checksum

Ident Frag.Offset

Total Length

TTL

Typ.Ser.

Fl.

Proto

Ver Len

Typ.Serv.: Precedence (0 = normal, 7 = control)D = Short delay wanted (best effort)T = High throughput wanted (best effort)R = High reliability wanted (best effort)


IP v4 Options

Class 0 Length

Option

– 1 : End of option list 1

– 2 : Security and handling restrictions 11

– 3 : Loose Source Routing var

– 7 : Record route var

– 9 : Strict Source Routing var

Class 2

Option

– 4 : Internet timestamp var


QOS Routing

Ser = D

Ser = T

Ser = R


IP and QOS

• Facts :



• Solutions :



– Use QOS resources of underlying network (ATM)




Multi Protocol Over ATM

Single or initial frame

ATM Network

= MPOA server


Multi Protocol Over ATM

Subsequent frames

ATM Network

= MPOA server








Multi Protocol Label Switching

= Ingres/Egres Router

Any Network

Add signaling protocol to network to allow establishment of virtual circuit for some data flows.


Multi Protocol Label Switching

IP datagramlabelX25 overhead

IP datagramlabelFR overhead

IP datagramlabelATM overhead

Optimizes IP address to VC number translationby explicitly identifying flows of datagramswith common QOS requirements.MPLS = attempt to standardize these labels(RFC 3031 - Jan 2001)


IP v6 Header

Source IP Address

Destination IP Address

Payload Length

Flow Label

Next Hdr Hop Lim.

Ver Pri

Flow = connection oriented communicationimplemented through connectionless service

Flow uniquely identified bysource addressflow label

Avoids label field between layer 2 and 3 overhead

Flow Label : enables MPLS in IP V6








The Future ???

IP

ATM

SDH

Application

IP+MPLS

ATM/FR

SDH

Application

IP+MPLS

ATM/FR

SDH

Application

IP+MPLS

ATM/FR

SDH

Application

Optical Fibers + WDM

IPv6

ATM/FR

SDH

Application

Documents

11-01-K.Steenhaut & J.Tiberghien - VUB 1 Telecommunications Concepts Chapter 4.2 IPv4 and Other Networks