Telecommunications Concepts

Chapter 4.2 IPv4 and Other Networks TelecommunicationsConcepts

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 Contents

The Internet SublayerIP approach Application 1 Application 2 Application 3 TCP UDP Internet Protocol any network

Transmitting IP Datagrams IP Datagram IP router IP router Underlying Network Frame Underlying Network Underlying Network

IP over Ethernet Application 1 Application 2 Application 3 TCP UDP Internet Protocol Ethernet

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. Address Resolution Protocol

1 1 IP over IEEE 802 LANs 4 4 3 3 802.2 cls 2b 2b 2a 2a IP addresses need to be translated into LAN addresses

1 1 IP over traditional LANs 4 4 3 3 2a 2a IP addresses need to be translated into LAN addresses

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. ReverseAddress Resolution Protocol

Directly linked Routers

General Purpose SDH Networks PABX PABX

IP Networks Router 4.2 4.1 1.2 3.2 4.3 1.1 3.3 1.3 5.2 2.1 1.4 5.1 2.2 5.3 6.1 7.2 7.1 2.3 6.3 6.2

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 ! Serial Line Internet 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 Point to Point Protocol TCP UDP Application, Transport & Network layers ? IP IPX PPP Physical layer Leased Lines PSTN ISDN ADSL GSM ?

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 P P PAdvantages over SLIP

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 ISDN

2 2 VCN IP datagram X25 overhead 1 1 IP over X25 4 4 3 3 3 3 X25 IP addresses need to be translated into X25 addresses

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 X25

1 1 FR overhead VCN IP datagram IP over Frame Relay 4 4 3 3 2 2 FR IP addresses need to be translated into PVC numbers

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 Frame Relay

Application 1 Application 2 Application 3 TCP-UDP IP aal aal ATM ATM IP over ATM Application 1 Application 2 Application 3 any network

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, but...

IP over ATM 4 4 3 3 AAL 1 1 ATM ATM/AAL overhead vcn IP datagram

ATM Adaptation Layer Data encapsulation Higher layer PDU pad AAL ATM header pad AAL

. 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 IP over ATM, solutions

Classical IP over ATM ATM Network Router ARP Server

Application 1 Application 2 Application 3 TCP-UDP IP LAN emulation Application 1 Application 2 Application 3 ??? ??? LLC any network ATM

. 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 IP over ATM, solutions

Bridge LES,BUS,LECS Servers LAN Emulation ATM Network Router

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

Header Checksum Source IP Address Destination IP Address Options Padding IP v4 Header (2) Ver Len Typ.Ser. Total Length Fl. Ident Frag.Offset TTL Proto 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)

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 IP v4 Options

QOS Routing Ser = D Ser = T Ser = R

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 (ATM) Traditional routing algorithms do not allow differentiation between datagrams with same destination. Additional intermediate protocols needed IP and QOS

= MPOA server Multi Protocol Over ATMSingle or initial frame ATM Network

= MPOA server Multi Protocol Over ATMSubsequent frames ATM Network

Any Network = Ingres/Egres Router Multi Protocol Label Switching Add signaling protocol to network to allow establishment of virtual circuit for some data flows.

label IP datagram X25 overhead FR overhead label IP datagram ATM overhead label IP datagram Multi Protocol Label Switching • Optimizes IP address to VC number translation • by explicitly identifying flows of datagrams • with common QOS requirements. • MPLS = attempt to standardize these labels • (RFC 3031 - Jan 2001)

Telecommunications Concepts