X 25 Overview An Introduction to X

X. 25 Overview

An Introduction to X. 25 Cloud LAN Protocol S S S X. 25 S LAN Protocol X. 25 Virtual Circuit • IP • Apple. Talk • Novell IPX • Banyan VINES • XNS • DECnet • ISO-CLNS • Apollo • Compressed TCP • Bridging

X. 25 Protocol Stack OSI Reference Model X. 25 Protocol 7 Application • 6 Presentation • 5 Session • 4 Transport • 3 Network X. 25 3 2 Data Link LAPB 2 1 Physical 1

X. 25 (X. 121) Addressing Format 4 decimal digits Up to 10 or 11 decimal digits Data Network ID Code Network Terminal Number • Addressing set by service provider

X. 25 Encapsulation IP Network X. 25 Data-Link Frame (LAPB) X. 25 Header IP Datagram • Protocol datagrams are reliably carried inside X. 25 frames

X. 25 Virtual Circuits Switched Virtual Circuits (SVCs) Permanent Virtual Circuits (PVCs) • Numbering for up to 4095 VCs per X. 25 interface

X. 25 Configuration Example IP Address: 10. 60. 8. 1 X. 121 Address: 311082194567 IP Address: 10. 60. 8. 2 X. 121 Address: 311082191234 S 1 S 0 X. 25 Cisco A Cisco B interface serial 1 interface serial 0 encapsulation x 25 address 311082194567 x 25 address 311082191234 ip address 10. 60. 8. 1 255. 248. 0 ip address 10. 60. 8. 2 255. 248. 0 x 25 map ip 10. 60. 8. 2 311082191234 broadcast x 25 map ip 10. 60. 8. 1 311082194567 broadcast

X. 25 Local and XOT Switching X. 25 PAD IP Internetwork Local Switching X. 25 PAD Remote Switching Router(config)# x 25 route [ # position ] x. 121 -address [ cud pattern ] interface type-number X. 25 PAD

Frame Relay Overview

Frame Relay Overview DCE or Frame Relay Switch DTE or CPE router CSU/DSU Frame Relay works here. • Virtual circuits make connections • Connection-oriented service

Frame Relay Terminology LMI 500=Active 400=Active DLCI=500 Local Access Loop=T 1 Local Access Loop=64 kbps DLCI=400 Local Access Loop=64 kbps

Frame Relay Terminology (cont. ) I am congested. BECN C FE N Bc=32 kbps CIR=64 kbps T 1

Selecting a Frame Relay Topology Full Mesh Partial Mesh Star (Hub and Spoke)

Multipoint Subinterfaces Configuration Example RTR 2 s 2. 1=10. 17. 0. 2/24 RTR 1 s 2. 2=10. 17. 0. 1/24 RTR 3 s 2. 1=10. 17. 0. 3/24 RTR 4 s 2. 1=10. 17. 0. 4/24

Multipoint Subinterfaces Configuration Example

! interface Serial 2 no ip address encapsulation frame-relay ! interface Serial 2. 2 multipoint ip address 10. 17. 0. 1 255. 0 bandwidth 64 frame-relay map ip 10. 17. 0. 2 120 broadcast frame-relay map ip 10. 17. 0. 3 130 broadcast frame-relay map ip 10. 17. 0. 4 140 broadcast ! router rip network 10. 0

Point-to-Point Subinterfaces Configuration Example 10. 17. 0. 0/24 s 2. 1 RTR 2 RTR 1 s 2. 2 s 2. 3 s 2. 4 10. 18. 0. 0/24 s 2. 1 10. 20. 0. 0/24 RTR 3 s 2. 1 RTR 4

Point-to-Point Subinterfaces Configuration Example

interface Serial 2 no ip address encapsulation frame-relay ! interface Serial 2. 2 point-to-point ip address 10. 17. 0. 1 255. 0 bandwidth 64 frame-relay interface-dlci 110 ! interface Serial 2. 3 point-to-point ip address 10. 18. 0. 1 255. 0 bandwidth 64 frame-relay interface-dlci 120 ! interface Serial 2. 4 point-to-point ip address 10. 20. 0. 1 255. 0 bandwidth 64 frame-relay interface-dlci 130

Common LAN Technologies

LAN Technology Overview Ethernet Token Ring FDDI Dual Ring

Ethernet and IEEE 802. 3 • Several framing variations exist for this common LAN technology

Ethernet Frame Variations Preamble DA 8 SA 6 Type 6 Data 2 FCS 4 Ethernet Frame Preamble 8 DA SA 6 Length 6 802. 3 Frame 2 802. 2 Header and Data FCS 4

Ethernet Frame Variations AA AA CTRL DSAP SSAP 802. 2 Frame Preamble DA 802. 3 Frame Ether Type CTRL SNAP Frame SA Length OUI Upper Layer Data IP, Apple. Talk DATA 802. 2 Header and Data FCS

High-Speed Ethernet Options • 100 Base. TX • 1000 Base. T/SX/LX/LH/ZX

Token Ring and IEEE 802. 5 Token Ring • IBM’s Token Ring is equivalent to IEEE 802. 5

Physical Layer: Token Ring/802. 5 Logical Topology MSAU Shielded or Unshielded Twisted-Pair • Logically a ring, but physically a star configuration to MAU relays

The Token Ring/802. 5 Interface Token Ring To 0 • Cisco router’s data link to Token Ring/802. 5 uses interface named To plus a number (for example, To 0)

Token Ring/802. 5 Operation T A T = 0 • Token Ring LANs continuously pass a token

Token Ring/802. 5 Operation T A T = 0 A T = 1 T Data • Token Ring LANs continuously pass a token or a Token Ring frame

Token Ring/802. 5 Operation T A A T = 0 T A T = 1 T Data • Token Ring LANs continuously pass a token or a Token Ring frame

Token Ring/802. 5 Media Control Access Control Field P P P T M R R R P Priority bits T Token bit M Monitor bit R Reservation bits • Fields in a frame determine priority and reservation for sharing media

FDDI 100 Mbps FDDI Dual Ring • Devices on FDDI maintain connectivity on dual counterrotating rings

FDDI Dual-Ring Reliability When a failure domain occurs. . .

FDDI Dual-Ring Reliability When a failure domain occurs. . .

FDDI Dual-Ring Reliability When a failure domain occurs. . . wrap primary and secondary rings. . . maintaining network integrity

ATM

ATM Basics Review • • • A compromise for voice, Voice data, and video Hardware-based cell relay Larger frames are segmented and reassembled at ATM endpoints Can span both LAN and WAN Scales from a few Mbps to multi-Gbps Qo. S defined/negotiated when initial connection is made Video Data ATM cells 48 -octet Payload ATM 53 -octet cells are switched in hardware

ATM Cell Processing TCP IP TCP Packet LLC App Data TCP Header App Data IP Header IP Datagram LLC/SNAP Convergence Sublayer TCP Header IP Header TCP Header App Data AAL 5 -PDU AAL 5 SAR-PDU - 48 Bytes SAR Sublayer 48 Bytes ATM 5 Bytes ATM Hdr AAL 5 SAR-PDU - 48 Bytes 53 Bytes ATM Cell PHY Transmission Convergence (STS 3 c, STM-1, DS 3, 4 B/5 B, . . . ) Physical Media (MMF, STP, UTP, Coax, …)

Virtual Path and Virtual Channels (VCs) ATM Physical Link Virtual Channel Connection (VCC) Virtual Path (VP) e. g. , OC-3, E 3, OC-12 Virtual Path (VP) Virtual Channels (VCs) Virtual Channel Connection (VCC) Contains Multiple VPs Virtual Path (VP) Contains Multiple VCs VC Logical Path between ATM End points Connection Identifier = VPI/VCI

Well-Known VPI/VCIs Terminating Connections Type Signaling ILMI PNNI VPI/VCI (Logical) Default (Physical) x/5 0/5 x/16 0/16 x/18 0/18

ATM Cell Header—UNI Format GFC VPI 4 8 VCI PT 8 7 6 5 CLP HEC 3 16 32 Bits 1 8 8 Bits CRC 4 3 2 Bits Bytes 1 GFC VPI 1 VPI VCI 2 3 VCI PT User data or maintenance flow Congestion experienced End of message (AAL 5) VCI PT CLP 4 5 HEC

ATM Cell Header—NNI Format VPI VCI 12 PT 8 7 6 5 4 3 2 HEC 3 16 32 Bits CLP 1 8 8 Bits CRC Bits Bytes 1 VPI VCI 2 3 VCI PT CLP 4 5 HEC • Larger VP field for trunking • Distinction not very useful for private network

VP Switching/VP Cross-Connect VCI 1 VCI 2 VPI 1 VPI 4 VCI 3 VCI 4 VPI 2 VPI 5 VCI 6 VPI 6 VCI 1 VCI 2 VCI 5 VCI 6 VPI 3 VP Switch • Switching based on VPI only (central office trunk switching)

VP and VC Switching VC Switch VCI 2 VCI 1 VPI 1 VCI 3 VPI 3 VCI 4 VPI 2 VCI 1 VCI 2 VPI 3 VPI 4 VP Switch VCI 3 VPI 5 VPI 1 VCI 4 VCI 1 VCI 2

ATM Switch Translation Table Input Output Port VPI/VCI Port 1 2/39 2 4/55 1 2/39 1 6/64 3 2/89 1 6/64 4/55 VPI/VCI 2/39 6/64 2 1 3 2/39 • ATM switches translate VPI/VCI values • VPI/VCI value unique only per interface— e. g. , locally significant and may be reused elsewhere in network

ATM Adaptation Layer Service Bit Rate Connection Timing Categories Mode Concern ATM Adaptation Layer (AAL) AAL 1 CBR (Constant) AAL 2 VBR (Variable) ATM Layer AAL 5 Physical Layer ABR UBR Yes Connection. Oriented No • Best effort with congestion feedback • Reliable delivery of bursty traffic if latency okay No • No guarantee • For SMDS (CBR) UBR Connection(Unless specified) • Bandwidth and throughput guaranteed • Good for voice and video • Best effort bandwidth and throughput • Good for live video, multimedia, LAN-to-LAN Connection. Oriented VBR AAL 3/4 Application Examples

AAL 5 Payload Frame Data Frame Convergence Sublayer (CS) Convergence Sublayer PDU SAR PDU AAL 5 SAR Sublayer SAR PDU ATM Layer 0 x 0 SAR PDU ATM Cell 0 x 0 ATM Cell • CS trailer Length CRC-32 • Cell header Type: empty, not EOM, EOM • Payload: 48 bytes • Primary AAL for data 0 x 1 ATM Cell

AAL 5—Frame and Cell Formats AAL 5 CPCS - PDU Frame = n x 48 bytes P A D User Data 0 -65535 bytes 0 -47 bytes Control (CPI and UU) 2 byte Payload Length 2 bytes CRC-32 4 bytes AAL 5 CPCS PDU Trailer SAR-PDU Payload = 48 bytes AAL 5 SAR PDU = 1 Cell Payload CPI UU PAD Common part indicator, current function: aligning the trailer to 8 bytes, currently unused and set to 0 User-to-user indication, currently unused and set to 0 0 -47 bytes • 53 = 5 (cell header) + 48 (payload)

ATM Signaling, ATM Address Formats

Switched Virtual Channels (SVCs) B-ICI Public ATM Network NNI UNI NNI Private ATM Network • SVC requires signaling ATM connection oriented • ATM Forum UNI 3. x/4. 0 signaling specification Based on ITU-T Q. 2931

Signaling Concept ATM Router A Connect to B OK Connect to B • Signaling request • Connection routed—setup path • Connection accepted/rejected • Data flow—along same path • Connection teardown Connect to B OK ATM Router B

ATM SVC Call Setup Calling Party Called Party Set Up Setup Call Proceeding Connect ACK ES Connect ACK ATM Network Connect ACK ES • Call set up in software • Cell switching in hardware • Dynamic call establishment (call setup) with appropriate parameters (e. g. , Qo. S: CLR, CTD, CDV)

ATM SVC Call Release Calling Party ATM Network Called Party Release Complete ES • Dynamic call teardown (call release) of virtual connection

Q. 2931 Call Control Q. 2931 SSCOP PD Call Ref Mes Info Type Len Elements • Q. 2931 call control message format at UNI

ATM Addressing Formats AFI DCC DSP E. 164 ESI HO-DSP ICD IDI Sel ICD High-order Part of DSP International Code Designator Initial domain identifier NSAP Selector AFI ICD AFI = 47 DCC Authority and Format Identifier Data Country Code Domain Specific Part ISDN (telephone) Number End-system Identifier (IEEE) ESI E. 164 AFI = 45 SEL ESI SEL DSP AFI DCC AFI = 39 SEL DSP