Advanced Computer Networks

Transcription

1 Advanced Computer s Introduction Course goals Advanced topics in ing cross-layer vision advanced functionalities design, performance Organization h course slides are not exhaustive - you must take notes and ask questions! Prof. Andrzej Duda duda@imag.fr Contents Introduction architectures Interconnection Layer bridges, spanning tree protocol, VLANs Interconnection Layer routing (R, OSPF, BGP) Congestion control Quality of service MPLS Wireless LANs and QoS Mobility Course support Web site L. Toutain "Réseaux locaux et Internet", me édition, Hermes, 00 C. Huitema "Le routage dans l'internet", Eyrolles, 99 R. Perlman "Interconnexions : ponts et routeurs", Addison-Wesley, 99 S. Keshav "An Engineering Approach to Computer ing", Addison Wesley, 997 Overview Introduction: structure, architecture and protocols Recall on layered protocol stacks Internet architecture layer - LANs layer of AS access s For each consider its architecture protocol architectures how entities cooperate? structure which entities are connected? related protocols how and where different functionalities are implemented? 6

2 Layered Protocol Stack Managing complexity a layer corresponds to an independent module (protocol entity) A layer supports common format - PDU (Protocol Data Unit) rules of cooperation: peer-peer procedures service interface: SAP (Service Access Point) Protocol entity provides a set of services, eg. connect, send multiplexing/demultiplexing construction/analysis of PDUs execution of procedures Protocol unit (PDU) header: control functions opaque Procedures actions to perform protocol functions: eg. lost packet retransmission 7 8 Internet protocol stack multiplexing demultiplexing SAP SAP procedures Protocol entity Protocol entity layer n layer n PDU PDU Lower layer protocols layer n- layer n- : supporting applications FTP, SMTP, HTTP, OSPF, R : - transfer TCP, UDP : routing of grams from source to destination Link: transfer between neighboring elements, Ethernet : bits on the wire Link 9 0 protocol stack LAN stack (IEEE) : native applications, other protocols LAN Emulation,, Signaling : - transfer SSCOP Adaptation: adapt the layer to different types of applications circuit emulation, real-time suitable for traffic : cell ing over virtual circuits : bits on the wire Adaptation Management: e.g. construct forwarding tables SNAP: Spanning Tree protocol (Logical Link Control): multiplex different protocols, X, SNAP (Medium Access Control): medium access 80. (Ethernet), 80. (Token Ring), 80. (Token Bus), 80. (Wi-Fi) : bits on the wire Data-link Management

3 Global Internet architecture architectures Logical structure ISP ISP ISP Core interconnected entities how entities cooperate Related protocols different functionalities GSM POTS LAN WLAN Access s GPRS modem over POTS Interconnection structure - layer Interconnection at layer layer (bridge) VLAN Switches (bridges) interconnect s logically separate groups of s (VLANs) managed by one entity Type of the broadcast Forwarding based on address flat address space forwarding tables: one entry per works if no loops careful management Spanning Tree protocol not scalable 6 L PDU ( Frame) L PDU ( Frame) (bridge) Switches are layer intermediate systems Ethernet v management SNAP 80. -link Transparent forwarding Management protocols (Spanning Tree, VLAN) layer 7 8

4 Interconnection structure - layer Interconnection at layer sub layer layer (bridge) VLAN Routers interconnect subs logically separate groups of s managed by one entity Forwarding based on address structured address space routing tables: aggregation of entries works if no loops - routing protocols (IGP - Internal Routing ) scalable inside one administrative domain 9 0 L PDU ( Frame) ( packet) L PDU ( Frame) routing OSPF naming configuration routing DNS DHCP R UDP control groups TCP transport application Routers are layer intermediate systems Explicit forwarding (bridge) has to know the address of the first Management protocols (control, routing, configuration) ICMP Ethernet v IGMP address resolution ARP -link Autonomous systems Long-haul links sub autonomous system layer layer border internal (bridge) VLAN Fiber at physical layer (SONET/) Dense Wave Division Multiplexing (DWDM) one color of the light λ Different technologies Frame Relay POS (Packet over SONET/) Type of the NBMA (Non Broadcast Multiple Access) or point-to-point Complex protocol hierarchies over

5 Internet - AS ( packet) autonomous system NAP, GIX, IXP cell cell ( packet) subs L PDU ( frame) border 6 Interconnection of AS Border s interconnect AS NAP or GIX, or IXP exchange of traffic - peering Route construction based on the path through a series of AS routing BGP TCP transport application based on administrative policies control routing tables: aggregation of entries works if no loops and at least one route - routing protocols (EGP - External Routing ) ICMP address resolution ARP 7 Ethernet v -link 8 Residential access Residential access layer modem POTS (phone ) Modem connects a to the first Point-to-point encapsulation () activate a connection authenticate the user negotiate address multiplex different protocols (, X) 9 0

6 ( packet) L PDU ( Frame) CHAP PAP header compression NCP LCP -link authentication negociation layer Residential access ( packet) layer modem over cell / DSLAM cell requires fixed address ATU-R modem/bridge/ DSLAM (ATU-C) DSL Access Multiplexer oa ( packet) L PDU ( frame) oa oe Ethernet oe Ethernet oe Ethernet ( packet) L PDU ( frame) /SNAP cell / cell cell modem over (oa) DSLAM multiple users share link bridge/ over Ethernet (oe) multiple users share link / DSLAM 6 6

7 Conclusion Complex architectures different types of s used as links Internet Rapid growth scalability No central control coherent development Three level hierarchy, sub, autonomous system manage complexity Advances larger address space - v6 performance - quality of service, e.g. DiffServ security - Virtual Private s (VPN) 7 7