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IP Transmission Technologies

IP Transmission Technologies. email WWW phone... SMTP HTTP RTP... TCP UDP… IP ethernet PPP… CSMA async sonet... copper fiber radio. Hourglass of TCP/IP Protocols. Transmission Technologies. Ethernet (LAN) Copper Fiber Wireless Satellite DVB-RCS

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IP Transmission Technologies

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  1. IP Transmission Technologies

  2. email WWW phone... SMTP HTTP RTP... TCP UDP… IP ethernet PPP… CSMA async sonet... copper fiber radio... Hourglass of TCP/IP Protocols

  3. Transmission Technologies • Ethernet (LAN) • Copper • Fiber • Wireless • Satellite DVB-RCS • Point-to-point Leased Line • E1, SDH, DSL,... • Packet-switched • X.25, Frame Relay • ATM • MPLS • QoS

  4. Types of Point to Point Protocols • SLIP over async • Very simple • IP only • Unreliable - no checksum • HDLC over sync • various proprietary versions • frames have checksum • PPP

  5. Link Control Protocol (LCP) Code Identifier Length Data PPP Flag Address Control Protocol LCP FCS Flag Cisco HDLC Flag Address Control Proprietary Data FCS Flag S S S S S DCE DTE S DTE DCE Leased Line V.35 V.35

  6. PPP • “SLIP done right” • Used for synchronous and asynchronous transmission • Extended negotiation mechanism • Multiple protocol support

  7. PPP and OSI model Network Layer IPCP IPXCP others PPP Network Control Protocol Data Link Layer LCP - Link Control Protocol Synchronous or Asynchronous Physical Media Physical Layer

  8. LCP Configuration Options

  9. PAP/CHAP • PAP • Password required • Unencrypted password sent via the link • Allows storage of encrypted passwords • CHAP • Challenge handshake • No passwords sent via the link • Need for storing unencrypted secrets

  10. Selecting a PPP Authentication Protocol PAP 2-Way Handshake Remote Router (SantaCruz) Central-Site Router (HQ) "santacruz, boardwalk" Accept/Reject • Passwords sent in cleartext • Peer in control of attempts username santacruz password boardwalk Hostname: santacruz Password: boardwalk

  11. Selecting a PPP Authentication Protocol CHAP 3-Way Handshake Remote Router (SantaCruz) Central-Site Router (HQ) Challenge Response Accept/Reject • Use “secret” known only to authenticator and peer username santacruz password boardwalk Hostname: santacruz Password: boardwalk

  12. Multilink PPP • Combining physical links into one logical bundle • Result: higher speed and lower latency • MPPP / Bonding • MPPP assembles/disassembles frames on the Data Link Layer • MPPP used for synchronous and asynchronous physical links • Bonding assembles/disassembles on the bit level

  13. Show ppp multilink

  14. X.25

  15. X.25 • 1970s • Data Terminal Equipment (DTE) • Data Circuit-terminating Equipment (DCE) • Packet Switching Exchange (PSE) • DCE provides clock

  16. X.25 topology

  17. Packet Assembler/Disassembler

  18. X.25 Stack

  19. LAPB Frame

  20. X.25 Data Link Control • Point to point full duplex data links • Correction of errors and congestion control • Encapsulation of data in variable length frames delimited by flags • Redundant error correction bits • Sliding window (8 or 128 frames)

  21. X.121 address

  22. X.121 address • Data Network Identification Code (DNIC) • National Terminal Number (NTN)

  23. Packet Level Protocol • Several circuits multiplexed • Sliding window error and congestion control for every VC • Call restriction, charging, QoS, ...

  24. VC Setup • PVC: permanent entry in “routing” table (static), substitute to leased lines • SVC: dynamic entry in “routing” table triggered by an “open” packet and torn down by “close” packet

  25. Frame Relay

  26. Characteristics • Introduced in 1984 but only (significantly) deployed in the late 1980s • L1 and 2 • Packet Switched technology: PVCs and SVCs • Connection-oriented data link layer communication • X.25 “lite”

  27. Differences with X.25 • Less robust • Assumes more reliable medium => • No retransmission of lost data • No windowing • Error control handled by higher layers • Higher performance and transmission efficiency

  28. Frame Relay Topology

  29. DLCI • Data Link Connection Identifier • Uniquely identify circuits • Assigned by service provider • Local significance only (except with LMI)

  30. DLCI

  31. Frame Format

  32. CIR • What you buy with a FR connection • Committed Information Rate • CIR= Committed Burst/Committed Time • Also Maximum Rate

  33. RTR2 RTR3 Frame Relay s0.1-DLCI=110 s0.2-DLCI=110 s0.3-DLCI=130 RTR1 s0.3-DLCI=120 s0.2-DLCI=130 s0.1-DLCI=120

  34. ATM Asynchronous Transfer Mode

  35. Characteristics • Originally designed to transmit voice, video and data over the same network • Cell switching • Each communication is assigned a timeslot • Timeslots are assigned on a demand-basis => asynchronous (as opposed to TDM)

  36. Cells • 53 bytes: 5 byte header + 48 byte payload • Tradeoff between voice world and data world: • Voice needs small payloads and low delay • Data needs big payload and less overhead

  37. ATM

  38. ATM Adaptation Layer (AAL) • Together with ATM layer, equivalent to Data Link layer in OSI model • AAL1: Connection Oriented => Voice and Video • AAL 3,4: Connection Oriented and Connectionless (similar to SMDS) • AAL 5: Connection Oriented and Connectionless for CLIP and LANE

  39. ATM AAL5

  40. ATM Sources

  41. ATM Addresses • ITU-T Standard: E.164 (Telephone #) • ATM Forum defined 20-byte NSAP Addresses for use in private networks • E.164 address used as prefix on NSAP • Mapped to IP addresses by ATM ARP (in CLIP)

  42. ATM QoS • Traffic Contract: peak bandwidth, average sustained bandwidth, burst size , … Similar to FR • Traffic Shaping (end device): Queuing, Buffering • Traffic Policing (switches): Enforces contract

  43. Path Establishment

  44. MPLS Terminology • LDP: Label Distribution Protocol • LSP: Label Switched Path • FEC: Forwarding Equivalence Class • LSR: Label Switching Router • LER: Label Edge Router

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