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Driving Forces of Network Evolution in the 90s: A Retrospective Analysis

Explore the evolution of core networks in the 1990s, from IP over Tx/Ex to tag switching, addressing performance, stability, and traffic control issues. Understand the transition towards high-speed and efficient network technologies.

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Driving Forces of Network Evolution in the 90s: A Retrospective Analysis

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  1. Lecture 2. Core network evolution D. Moltchanov, TUT, Spring 2010 D. Moltchanov, TUT, Spring 2008

  2. Outline • What drives network evolution • Evolution of L3 network • Evolution of L1/L2 networks • Vendors’ view • Operator’s view • Next lectures

  3. What drives network evolution • Money: Make more revenue • How: better networks – more users – more revenue • How: reduce CAPEX and OPEX • Converge to single multi-service network • How: the only choice - everything over IP • Several single service networks: OPEX ~ 70% CAPEX • Optimize network resources and capabilities • How: traffic engineering • Enhance reliability/survivability • How: traffic engineering • Enhance management performance • How: simple and well-defined methodologies • Enable cost-effective provisioning of new services • How: multi-service network

  4. Beginning of 90s: IP over Tx/Ex • Beginning on 90th: • Transport network: E1 (T1), E3 (T3) • Only few transport nodes to configure and control • Manual configuration is feasible • Routers’ performance is unstable • IGPs metrics are sufficient to control the load • Traffic chooses the link with the least metric • Path via C is not used

  5. Beginning of 90s: problems • Problems with IP networks in the middle of 90: • Insufficient throughput of transport network • Topology of the transport network gets complicated! • Manual configuration is no longer feasible! • Unstable and insufficient performance of routers • We needed a breakthrough in hardware and software! • Using IGP’s metric is not the best way to control traffic • Topology of the transport network gets complicated! • Routing does not depend on the traffic • IGP: only topology is taken into account • Analysis IP header is too slow for high speed networking • Basically, we needed: • High speed transport network • Fast and stable forwarding at IP • Traffic control features

  6. Middle of 90s: IPoverATM • Addressing the needs: • SDH/SONET • High-speed low layer transport • ATM • Forwarding: fast and reliable • VC/VP switching • IP over ATM • Virtual(!) topology for traffic control • Advantages of IP/ATM • High-speed technology • Traffic control • Usage statistics for each VC, etc. • SDH/ATM/IP: logical networks (overlays)

  7. Middle of 90s: Logical networks • Physical network • Logical IP network

  8. Middle of 90s: +/- of IPoverATM: • Operating ATM network is (relatively) simple • Software estimates the path based on • Links load and type of traffic on links • Virtual network • Primary and secondary paths • Automatic switch configuration • Shortcomings of IP/ATM • Problems with topology • Physical network is not logical • Huge overhead (control information) • ATM: ~20% are headers • STM-16(2.4Gbps): 498Mbps, STM-64 (9.9Gbps): 1.99Gbps – headers • Do not forget IP/TCP headers! • High speeds of ATM are still not fully used by IP • Performance of IP equipment is still limited

  9. End of 90s • End of 90s: • Breakthrough in routers: high-speed routers • High-speed hardware • New advanced software • Rise of giant vendors: Cisco, Nortel, Alcatel, Ericsson, Nokia • Result: stable performance of IP routers • There were two ways to the future: • Continue with IP over ATM • Huge overhead (only ATM gives ~20%) • Propose new high-speed technology • Low overhead! • Compatible with IP! • Automatic traffic control: • path selection, fast reroute, etc. • It should be a compromise between VC and routing

  10. End of 90s:Cisco’s tag switching • The main aim: • Speed up the packet treatment in routers • Allow automatic traffic control • Tag switching:Cisco Systems • Proprietary solution • Tag is added to each packet • Tag info: next hop • Standards:IETF drafts • ‘Tag Distribution Protocol’ • ‘Tag Switching Architecture Overview’ • ‘Use of Flow Label for Tag Switching’ • ‘Use of Tag Switching With ATM’ • ‘Tag Switching: Tag Stack Encoding’

  11. End of 90s:tag switching • Two basic components • Forwarding • Packet forwarding to the next hop • Basis:tag info (value) • Control • Getting and distributing info regarding the next hops • How tag is carried out: • Separate 2.5 level header • Frame header at the data-link layer • For example,ATM • Packet header at the network layer • For example, IPv6, “Flow label” field

  12. End of 90s:tag switching • Forwarding: • Each node maintains tag information database • Tag Information Base (TIB): forwarding table • Correspondence: {incoming tag, interface} – {outgoing tag, interface} • When a packet with tag is received • Node looks for entry inTIB • If exists: tag is changed, packet is forwarded to the outgoing interface • Advantages of tag switching: • High speed due to • Strict correspondence algorithm for forwarding • Short and fixed length tag • Forwarding is unified • One-to-one:one outgoing tag • One-to-many:a number of outgoing tags • Traffic engineering is very easy to do • Control is well isolated from forwarding

  13. Beginning of 2000s: MPLS • What is that? • Very similar to ATM • Successor of tag switching • Multi-protocol label switching • Actually: fast packet switching technology • Operates between layers 2 and 3 • Much faster than IP • MPLS combines advantages of: • АТМ:switching • IP:routing

  14. Beginning of 2000s:MPLS philosophy • Traditional routing • IP packet is routed hop-by-hop • Hop-by-hop routing • Decision regarding the next hop is made independently • IP header is analyzed in each router • IP header contains many fields • HOP-BY-HOP! • MPLS approach • IP header is analyzed only once: source routing • At the entrance to MPLS domain • Packet is associated with a certain flow • Flow is identified with a label • Only label is then analyzed in the core of a domain • SOURCE ROUTING!

  15. Beginning of 2000s:traffic engineering • Traditional traffic control • Chose a shortest path • Avoid node/link failures: possible • Avoid overloaded paths: not possible • MPLS traffic control • Creating virtual switched paths • LSP, Label-Switched Path • Analog to virtual circuitsinATM • We control how traffic crosses the network • Packet on a switched path • No delivery guarantees • Priorities exist • Intermediate nodes use label value to switch • Reliability: primary and secondary path

  16. Beginning of 2000s: +/- of MPLS • Fast forwarding • Label is faster to analyze than several fields • Low overhead • Header overhead is really small (compare to ATM) • Traffic engineering • Very important feature making MPLS widespread • Single, integrated network • Can still run above ATM/FR etc. • Developed specifically for IP

  17. Up to 2005: GMPLS • Generalized MPLS • Logical evolution and generalizationof MPLS • Allows to switch at 1, 2, 3 layers • Setting up LSP between identical bearers • GMPLS standardization • IETF RFC 3471: labels encoding • Usage forSONET/SDT • draft-ietf-ccamp-gmpls-sonet-sdh-08.txt • LSP management protocol • draft-ietf-ccamp-lmp-10.txt • Extensions ofOSPFforGMPLS support • draft-ietf-ccamp-ospf-gmpls-extensions-04.txt • Routing requirements forGMPLS support • draft-ietf-ccamp-gmpls-routing-09.txt • RSVP-TE extensions for optical networks • draft-ietf-ccamp-gmpls-rsvp-te-ason-02.txt

  18. Up to 2005: basic idea of GMPLS • Basic idea ofMPLS • Provide faster forwarding compared to plain IP • Provide better traffic engineering compared to OSPF or IS-IS • Basic idea of GMPLS • Create LSP at any layer • Flexibility of overlays construction • No difference whether it is • IPpacket • TDM SDH/SONET frame • DWDM wavelength • Each GMPLS node • Support label distribution • Set up LSP

  19. Up to 2005: GMPLS capabilities • Four types ofLSP • Optically switched • Fiber-switched capable (FSC) • Switching fibers • Lambda switched • Lambda-switched capable (LSC) • Switching wavelengths • Adapted forDWDM (Dense Wavelength Division Multiplexing) • TDM switched • TDM-switched capable (TSC) • Switching for SDH/SONET • Packet switched • Packet-switched capable • Switching for IP routers (MPLS), ATM switches, etc. • More flexiblecompared to MPLS • Contains next hop identifier • Fiber port, TDM slot, DWDMwavelength,…

  20. Physical network evolution • Up to 1990 • Tx/Ex networks • T1/E1, T3/E3 are mostly used • Relatively slow technologies (E1: 2Mbps, E3: 34 Mbps) • There was no need for more than 100Mbps • 1990 – 2000 • SDH/SONET • Very high speed up to several Gbps • 2000 - now • (D)WDM • Up to few Tbps • Nowadays: DWDM

  21. Vendors nowadays • IP/MPLS solutions • Why? • Still in agreement with ‘everything over IP’ • Traffic engineering is crucial • Fast forwarding is crucial • Software update makes MPLS switch • IP-based solutions can still be used • Experience of IP networks • Operators choice! • Who provides equipment • Cisco • Juniper • Riverstone • …

  22. Operators nowadays • IP/MPLS solutions • Remember, operators are much more realistic! • What are operators’ visions • Verizon • DiffServ/MPLS • Level3 • DiffServ/MPLS • Very strong QoS support • British Telecom • Overprovisioning/DiffServ/MPLS • Proprietary weak and simple TE features • Telecom Italia • Overprovisioning/DiffServ/MPLS • Strong QoS support

  23. Evolution strategies: Verizon • Single IP/MPLS core network • RSVP-TE is used for label distribution • IS-IS-TE and BGP as intra- and inter-domain routing • Traffic engineering • Load balancing + MPLS fast reroute for reliability • MPLS-based VPNs • Especially, VPLS • BGP/MPLS VPN and VPWS-martini

  24. Evolution strategies: Verizon’s bearers • Transmission network • Completely replace copper wire by fiber optics • Use DWDM • Evolve SONET further • Fiber to home • Logical network • MPLS+DiffServ • QoS across multiple domains • Edge equipment • Traffic control, e.g. monitoring, labeling, COS mapping • AQM should be used e.g. RED, RIO

  25. Evolution strategies: Level3 • IP MPLS • MPLS-based VPNs • VPLS • BGP/MPLS (RFC 2547) • End-to-end QoS • Does not recommend overprovisioning in MPLS backbone • Service differentiation of DiffServ • Bandwidth reservation of MPLS • QoS/COS support even in backbone • Other operators believe in QoS only in edge networks • Level3’s solution: DiffServ/MPLS

  26. Evolution strategies: BT • Simplicity is the way to the future • Multi-service access nodes at edges • Support softswitches for narrowband voice • SIP-based IMS for broadband multimedia • By 2007 50% PSTN exchanges have been replaced • Core network: IP/MPLS • Classic TE is too complex • Develop its own proprietary simple TE • QoS in access network: fiber networks, overprovisioning • Transmission backbone: DWDM

  27. Evolution strategies: Telecom Italia • IP/MPLS-based optical backbone backbone • Core network • MPLS-TE with OSPF-TE for bandwidth guarantees • DiffServ for service differentiation • MPLS-based VPNs • Access network • Fiber to home • xDSL for copper wire access • Transmission backbone: DWDM

  28. Evolution strategies: summary • Everything over IP • Most of operators agree on that • Build backbone using IP-MPLS-DWDM • Use MPLS-based VPNs • Build access using xDSL and BPON • Deploy QoS in core using • DiffServ for service differentiation • MPLS for bandwidth reservation • Overprovision to some degree • Introduce new services, e.g. IPTV • We consider everything related to IP/MPLS/DiffServ/VPN

  29. Evolution strategies: QoS? • Do we really need special mechanisms? • Resource reservation? • Service differentiation? • Is traffic engineering enough? Some think so • Put some routers • Balance load • Upgrade PHY network • Killer application nowadays: P2P • 60-70% of all traffic (BitTorrent ~20%) and continue to grow • P2P streaming is still in his early stages and evolves very fast • Overlays that do not care about underlying network • Non-optimized solutions at all in terms of resource usage • “Overprovisioned” backbones are becoming bottlenecks… • We will always have enough traffic to fill the network…

  30. Is providing QoS fair to end users? • Prior to year ~2000 • No doubts about that • I pay, you guarantee… • Nowadays some new trends • Network neutrality initiative • What? Internet traffic should be treated equally • Why? Operators may try to block content, degrade performance • Advocates: network is simply a bearer for services • Critics: congestions, searching for a problem • A lot of non-related stuff… • More at http://en.wikipedia.org/wiki/Network_neutrality

  31. Summary • Driving force: more revenue… • Support more users • Decrease CAPEX and OPEX • Enable higher access rates • Single multi-service network • Enhance disaster/failure recovery • Optimize resources • Everything is IP based • Main directions • Everything for IP • Higher PHY rates • Simple but robust control • Reduce CAPEX when enabling a new services

  32. What we are going to consider • Lecture 3: Basics of MPLS • Label encoding, LSR operations, LSPs • Label distribution protocols (LDP) • Lecture 4: Traffic engineering in MPLS • CR-LDP, RSVP-TE • Bandwidth reservation, interception, fast-reroute, etc. • Lecture 5: DiffServ/MPLS • Problems of DiffServ and MPLS • DiffServ-aware MPLS TE • Lecture 6: L2 MPLS VPN • VPWS, VPLS, HVPLS, IPLS • Modes, signaling, operation in details • Lecture 7: L3 MPLS VPN: BGP/MPLS (2547 VPN) • Modes, signaling, operation in details • Configuration examples

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