1 / 14

Connecting Networks by Relays

Layer 1: Repeater / Hub Layer 2: Bridge / Switch Self-learning bridges Spanning-tree algorithm Source routing bridges Remote bridges Layer 3: Router / Layer 3 Gateway / Intermediate Systems Types Circuit switching Message switching Packet switching Virtual circuit switching Services

kellylsmith
Télécharger la présentation

Connecting Networks by Relays

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Layer 1: Repeater / Hub Layer 2: Bridge / Switch Self-learning bridges Spanning-tree algorithm Source routing bridges Remote bridges Layer 3: Router / Layer 3 Gateway / Intermediate Systems Types Circuit switching Message switching Packet switching Virtual circuit switching Services Connection-oriented Connection setup QoS negotation Flow control Connectionless Unreliable connections No flow control Layer 4 - 5: Gateway / Protocol Converter Virtual circuit setup End system Intermediate system End system 5 5 Application layer B A 0 C 0 H 0 C 1 C H 1 A 0 B 0 D 0 A 1 F 0 B 1 D 1 H 2 F 1 E 0 H 0 A F 0 H 0 E 1 Gateway D 2 IN OUT H 0 4 B 0 4 Transport layer D H 1 E 0 C 0 H 0 B 0 E 1 C 1 H 1 H 2 B 3 1 Router F 0 H 2 3 Network layer H 3 E 2 F 1 H 3 H 4 E 3 C 2 F 0 2 Bridge 2 Data link layer E F A 0 F 0 E 0 D 0 1 A 1 H 0 B Repeater 0 D 1 1 Physical layer A 2 C 0 B 1 H 0 A 3 C 1 D 0 B 0 Connecting Networks by Relays

  2. Address resolution ARP Use broadcast to search for an IP address ARP and routing RARP Use broadcast to acquire own IP address DHCP RARP improvement H H H H H H H H H H H H RARP Response RARP Request ARP Response ARP Request source source source source @IP: 9.228.50.3 @IP: 9.228.50.8 @IP: 9.228.50.3 @IP: @IP: 9.228.50.3 @IP: unknown @IP: 9.228.50.3 @HW: 0xaa @HW: 0xa3e @HW: 0xaa @HW: 0xa3e @HW: 0xa3e @HW: 0xaa @HW: 0xa3e target target target target @IP: @IP: 9.228.50.8 @IP: 9.228.50.8 @IP: 9.228.50.3 @HW: 0xaa @HW: 0xaa @HW: 0xaa @HW: Internet

  3. Routing Routing tables Direct routing / interior protocols Indirect routing / exterior protocols Autonomous systems AS, AS backbone area, area Router classes AS boundary routers Backbone routers Area border routers Internal routers EGP Open Shortest Path First Link state routing Border Gateway Protocol Distance path mechanism Multicast routing Spanning tree Link state routing Reverse path forwarding with pruning Core-based tree Reverse path broadcast Truncated reverse path broadcast Internet

  4. Routing define the route of packets through the network Routing algorithm Defines on which outgoing line an incoming packet will be transmitted Desired properties Correctness Simplicity Robustness Stability Fairness Optimality Optimality principle Sink trees Route determination Datagram Virtual circuit Topology, link utilization, etc. information desti- nation link Routing Process Router A 0 B 3 Routing table C 1 Fills & Updates D 4 Uses & Looks up Data packets Forwarding Process Incoming lines Outgoing lines Routing Routing table and packet forwarding

  5. Classes of routing algorithm Non-adaptive Non-adaptive shortest path routing Flooding and selective flooding Adaptive Centralized routing Isolated routing Backward learning Distributed routing Distance vector routing Count-to-infinity problem Split-horizon Link state routing Definitions of distance Oscillations (route flapping) A I H K line D B (2,A) C (●,-) A 0 A B C 24 20 21 8 A B 12 36 31 28 20 A C 25 E (●,-) 28 I 18 19 36 D 40 G A D (●,-) 20 H 27 8 24 E H F (●,-) E 14 F 17 I 7 30 22 F 23 30 I 20 19 40 G 18 H (●,-) G (6,A) 18 H 31 6 31 H 17 I J K L 20 0 19 12 H I 21 0 14 22 10 I J 9 11 7 10 0 - K 24 22 22 0 6 K L 29 7 33 9 9 15 K 2 3 JA 8 JI 10 JH 12 JK 6 3 2 delay 2 1 2 6 2 4 Routing Dijkstra shortest path Distance Vector Routing Link State Routing

  6. Internet Protocol Stack IP Connectionless datagram server Segmentation / reassembly Route recording and source routing IP networks IPv4 Addressing Network classes Subnetworks Netmasks to find subnetworks CIDR Longest match prefix to find subnetworks IPv4 vs IPv6 SMTP HTTP FTP TELNET NFS RTP Application layer 14 16 e.g. address 129.8.7.2: 1 0 Network Host Subnet Host subnet addresswith netmask use either 129.8.4.0/255.255.252.0 or 129.8.4.0/22 TCP UDP Transport layer & & 1 1 1 0 0 1 1 0 0 0 1 0 1 0 0 1 0 0 0 0 1 1 1 1 0 0 1 1 0 0 1 0 0 1 0 0 1 1 1 1 0 0 1 0 0 1 0 0 0 1 0 0 1 0 0 1 0 1 0 0 0 0 1 1 1 1 1 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 0 0 0 0 Subnet mask: Subnet address: IP + ICMP + ARP 6 10 Network layer Data link and Physical layer WANs LLC & MAC LANs ATM physical MANs Internet Internet Protocols IPv4 address, netmask and subnet address

  7. Transport layer protocol ISO Transport layer protocol depends on the quality of the network layer service ISO Network types A, B, C Transport protocol classes 0 – 4 Internet protocols User Datagram Protocol Transmission Control Protocol CLOSED Timeout Send SYN Recv SYN Send SYN ACK LISTEN Send SYN Recv RST Recv SYN Send SYN ACK SYN RCVD SYN SENT Recv SYN ACK Send ACK Recv ACK Send FIN ESTABLISHED CLOSE WAIT LAST ACK Recv FIN Send ACK Send FIN Send FIN Recv FIN Send ACK FIN WAIT 1 CLOSING Recv FIN ACK Send ACK Recv ACK Recv ACK Timeout FIN WAIT 2 TIME WAIT Recv FIN Send ACK Transport Protocols & Network Services TCP state machine

  8. TCP • Features • IP fragmentation vs TCP segmentation • RTT estimation for timer management • Initial sequence number allocation • Reuse of session identifiers • High bandwidth or long-lived slow sessions • Limit transmission rate • Both needed • Flow Control • Receiver capacity • Congestion Control • Network capacity

  9. Approaches Sliding window / static buffer allocation Sliding window / no buffer allocation Credit mechanism TCP’s flow control Sliding window and credit mechanism Nagle’s algorithm Silly window problem Sender Receiver A wants 8 buffers <req 8 buffers> B grants messages 0-3 only A has 3 buffers left <cred=4> A has 2 buffers left Message lost <seq=0, data=m0> <seq=1, data=m1> Message lost but A thinks it has 1 left B acknowledges 0 and 1 permits 2-4 <seq=2, data=m2> <ack=1, cred=3> A has 1 buffer left <seq=3, data=m3> Everything acknowledged but no free buffers <seq=4, data=m4> A has 0 buffer left, must stop <seq=2, data=m2> A times out and retransmits B found a new buffer somewhere <ack=4, cred=0> A still blocked <ack=4, cred=1> <ack=4, cred=2> A has 1 buffer left A may now send next msg. <seq=5, data=m5> A is now blocked again <seq=6, data=m6> A has 1 buffer left <ack=6, cred=0> A is now blocked again <ack=6, cred=4> time time A still blocked Flow Control TCP credit mechanism

  10. Congestion control Can worsen without care Approaches Repair Packet dropping Max buffer, min buffer, content related Choke packets Threshold and history, several levels Fair queueing Avoid Traffic shaping Leaky bucket Token bucket Reservation Original packet arrival B C Smoothed stream Peak rate A D time E F Congestion Control Choke packets Traffic shaping

  11. sender receiver 30 20 10 25 15 65 60 70 40 50 80 35 75 55 45 5 time Congestion Control and Avoidance • Congestion control with TCP • Additive increase, multiplicative decrease • Congestion Window Development • Slow start • Congestion window threshold • Congestion avoidance phase • Decrease • Missing ACKs • Timeout • Congestion avoidance with RED and ECN • Random Early Detection • Drop packets randomly when IS queues fill up • Early Congestion Notification • Mark packets instead of dropping when IS queues fill up TCP congestion control Router queues with RED and ECN

  12. Quality of Service • QoS: Characterizes the well defined, controllable behavior of a system with regard to quantitatively measurable parameters • Techniques to Fulfill Requirements • Delay and jitter • Reservation, Buffering, Scaling • Continuity • Real-time packet re-ordering, Loss detection and compensation, Retransmission, Forward error correction, Stream switching • Synchronity • Fate-sharing and route-sharing, Time-stamped packets, Multiplexing, Buffering, Smoothing • QoS negotiation • Resource reservation • Styles • Sender-oriented • Receiver-oriented • combined

  13. Multimedia Protocols • Multimedia • Time-independent media  discrete media • Time-dependent media  continuous media • Interdependent media  multimedia • Application level framing • Applications know their needs, e.g. ordering and loss • Application defines data unit size • Try to avoid segmentation • Integrated layer processing • Process several layers at once • Ordering constraints exist

  14. RTP/RTCP Real-time Transport Protocol ALF and ILP RTP Profiles Sequencing, synchronization,payload identification, quality feedbackand session information Multicast, mixers, translators No reliability, no QoS support Signaling protocols RTSP Useful for Video-on-Demand, Near Video-on-Demand, live broadcasts SIP Useful for internettelephony andconferencing Application Application Decoding Encoding Encoding Decoding RTP RTCP RTCP RTP UDP/IP UDP/IP Multimedia Protocols RTP/RTCP interaction RTSP signalling SIP signalling

More Related