OverviewBasic conceptsPhysical Layer Protocols and InterfacesData Link Layer protocolsLLC and MAC Sublayer ProtocolsSwitching in the LAN Environment

Basic ConceptsInterfaces provide boundaries between different types of

hardwareProtocols provide rules, conventions, and the intelligence to

pass data over these interfaces.Protocols can also act as interfaces, defined as interface

protocols (ex. DTE-to-DCE signaling)Both interfaces and protocols must be compatible for

accurate and efficient data transport.

Physical Layer ConceptsDTE is typically a computer or terminal which acts as an end point for

transmitted and received dataDCE is typically a modem or communication device for data transportA null modem is used to connect two DTE devices such as a terminal

and an computerRefer to Figure 7.1 (p. 231)Physical layer protocols provide both electrical and mechanical

interfaces to the transport medium

Physical MediaUnshielded twisted pair: found in most buildings, is the least

expensive, and has high error ratesShielded twisted pair: protected from interference, low error rate,

more expensiveFiber Optics: advantage of resistance to electromagnetic signals, not

affected by crosstalk, large bandwidth, high speed of transmission

RS-232, EIA-232-E, EIA-449 and ITU-T V.24/V.28

RS-232-C provides a D-shaped 25-pin connector DTE interface to voice-grade modems (DCE)

EIA-232-E is a more recently adopted standardITU-T V.24 defines the physical interface and V.28 defines

the electrical interface (similar to RS-232)RS-449 is an improved version of RS-232 (longer distance,

higher speed, uses 37-pin connector)RS-423A offers an improvement of up to 3000 kbps speed

and operates in “unbalanced” transmission mode

ITU-T X.21, X.21bisX.21 eliminates the restrictions imposed by RS-232-C by using

balanced signaling and two wires for each circuitX.21 uses a 15-pin connector and operates only in synchronous

modeIt provides a balanced and unbalanced mode of operationIt can not have the capability to pass control information during data

transfer (as opposed to RD-232-C)The X.21bis interim standard was developed as a migration from the

RS-232-C, EIA-232-D, and V.24 standards to X.21

ITU-T I.430 and I.431Two standards for ISDN:

Basic Rate Interface (BRI) defined in the ITU-T I.430 standardPrimary Rate Interface (PRI) defined in the ITU-T I.431 standard

BRI and PRI interfaces are part of the specifications for Narrow-band ISDN (N-ISDN)

The physical interface in ISDN is one part of the D-channel protocol, and defines a full-duplex synchronous connection between the TE layer 1 terminal side of the basic access interface and the NT layer 1 terminal side of the basic access interface

Refer to Figure 7.2 (p. 235)

ITU-T I.430 and I.431 (continue…)Basic Rate Interface (BRI)

Two 64 kbps user data channels and one 16 kbps control, it is also referred as 2B+D

It is used for customer access devices such as the ISDN voice, data, and videophone

Primary Rate Interface (PRI)Twenty three 64kbps data channels and one 64 kbps signaling channel, it is

also referred as 23B+D.It is used for large amounts of bandwidth such as Private Branch Exchange

(PBX) and LAN servers.PRI is becoming the access method of choice for private access to the

Internet

ITU-T I.430 and I.431 (continue…)

• One ISDN feature that is particularly useful for achieving higher aggregate channel bandwidth rates than 64 kbps within a signle PRI is the Bandwidth-ON-Demand INteroparability Group (BONDING) standard• BONDING enables an ISDN device to act as an inverse multiplexer function by splitting a single data stream over multiple 64 kbps channels.•BONDING has the required delay calculating mechanisms to assure equal delay across all channels.

T1/E1 and D4/ESF Framing and FormattingA T1 consists of 24 channels with 8 bits per channel with a

time frame of 125 s.This adds up to 192 bits per frame T1 frame, with a framing

bit added for a total of 193 bits per frame.The transmission rate of the T1 is 8000 frames per second,

and includes an 8 kbps overhead channel.E1 is the European standard of the T1, and offers 2.048

Mbps bandwidth.The D4 12-frame superframe concept allows the 8 kbps

overhead on each T1 channel to be used for frame synchronization and signaling.

D4 framing formats can provide nonchannelized or channelized (as in DS0) circuits.

T1/E1 and D4/ESF Framing and Formatting (Continue…)

•Extended Superframe Format (ESF) is an enhancement to D4 framing.•With ESF, both the carrier and the user can “nonintrusively” monitor the performance of private lines.•The advantage to ESF is the capability for remote monitoring and problem detection, without having to take the circuit out of service in order to test (this is called “nonintrusive”)•If ESF is implemented in conjunction with intelligent network equipment, errors affecting performance can be detected and corrected transparently to the user

AMI and B8ZS Line Coding56 kbps channels use a technique called Alternate Mark Inversion

(AMI)A process called “bit stuffing” is used to set the Lease Significant

Bit (LSB) in every byte to 1, and thus it is not available for user traffic.

Bipolar Eight Zero Substitution (B8ZS) is used in the case of 64 kbps, or “clear channel” service.

B8ZS allows the entire bandwidth of 64 kbps to be usedThis is a requirement for 64 kbps frame relay network access.Remember that either a CSU or a DSU is capable of providing

either AMI or B8ZS coding, so make sure you have the correct device

High-Speed Serial Interface (HSSI)It is a physical interface operating at speeds up to 52

Mbps.It was designed to become the standard interface

between the DS3 rate of 45 Mbps and the OC-1 SONET interface of 51.84 Mbps for everything from WAN connectivity to a DTE-to-DCE direct-channel interface.

It is a hardware as well as a software interface configured to handle a high-speed frame relay interface

High-Performance Parallel Interface (HIPPI)It is a high-speed broadband parallel point-to-point channel

(interface) for supercomputer networking.

Enterprise Systems Connection Architecture (ESCON)ESCON provides high-speed, direct-channel connectivity for VM-

and VSE- based system processors, Direct-Access Storage Devices (DASD), and peripherals.

Primary support is for IBM 3990 storage control and application software

ESCON transfers data through synchronous, variable-length frames as opposed to the older byte-by-byte interface.

Fiber ChannelFCS defines a high-speed data-transfer interface for connecting

and transferring data between computing devices (workstations to supercomputers)

FCS works over both electrical and optical media, and supports full-duplex data rates from 133 Mbps to 1062 Mbps over distances up to 10 km.

Topologies include point-to-point, loop, and switch matrix.

IEEE 802 Physical InterfacesEthernetIEEE 802.3 with synchronous interface standard provided by RS-

232 or V.35Recognition of the presence or absence of the control of the

Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

Data transport, and translation of signaling from physical to MAC layer.

Five types: 1BASE5, 10BASE2, 10BASE5, 10BASET, an d10BROAD36

All Ethernet interfaces operate at a 10 Mbps bus speed for IEEE 802.3 and Version 1.0 and 2.0 Ethernet frame format.

Token Bus and Token RingThere are nine types of Token Bus physical interfaces. These interfaces fit into two categories: the broadband coaxial and

the carrier-band coaxial, both supporting 1, 5, and 10 MbpsPhysical interface for IEEE 802.4 Token Bus and IEEE 802.5 Toekn

Ring is the dB connector, interfacing the IBM Type 1 shielded twisted-pair cable.

Token Ring wiring is usually run in Type 1 (2-pair STP), Type 2 (4-pair STP), Type 3 (UTP), and Type 5 (fiber-optic cable)

Token Ring interfaces at either 4 Mbps or 16 Mbps through an IEEE 802.5 interface, and uses 802.2 Type 1 LLC support.

Refer to Figure 7.8 (p. 243)

Refer to Table 7.1 (p. 244)Refer to Table 7.2 (p. 245)

Binary Synchronous Control (BSC or Bisync)It was developed by IBM as an asynchronous half-duplex, point-

to-point or multipoint, character-oriented protocol for bidirectional transmissions of character-oriented-data

It consists of control codes to manage transmission of character-coded user information based on EBCDIC character set

Refer to Figure 7.9 (p. 256)

Digital Data Communications Message Protocol (DDCMP)Proprietary protocol developed by DECProvides a byte-count-oriented protocol transmitted either

asynchronously or synchronously over half- or full-duplex circuits on point-to-point or multipoint topologies

It also provides for supervisory and information frames, where this information would replace the information field

Refer to Figure 7.10 (p 246)

Synchronous Data Link Control (SDLC)Bit-oriented protocol developed by IBM and adopted by the ISOThe ITU-T also developed two standards based upon SDLC

The ITU-T Link Access Procedure Balanced (LAPB) is the X.25 implementation of SDLC

The ITU-T Link Access Procedure-D (LAPD) is the ASDN and Frame Relay (LAPF) HDLC-based implementation of SDLC

SDLC can operate in either multipoint or point-to-point, switched or dedicated circuit, and full- or half duplex operation

IT is replacing the less efficient BSC protocolRefer to Figure 7.11 (p. 247)

High-Level Data Link Control (HDLC)Most popular protocol for data link control implementations (level

2)It forms the basis for ISDN and Frame relay protocols and

servicesIt is a bit-oriented, simplex, half-duplex, or full-duplex and passes

variable-bit length streams over either a point-to-point or multipoint configuration

It also operates over either dedicated or switched facilities

High-Level Data Link Control (HDLC) (Continue…)There are two types of point-to-point link structures:

Balanced Mode: a primary station transmits commands to and receives responses from a secondary station

Unbalanced Mode: a receiving station acts as a primary and secondary station with the capability of sending either a command or a response

Refer to Figure 7.12 (p. 248)Refer to Figure 7.13 (p. 258)HDLC has three types of data-transfer modes

“unbalanced” Normal Response Mode (NRM)Asynchronous Balanced Mode (ABM)“unbalanced” Asynchronous Response Mode (ARM)

Refer to Figure 7.14 (p. 249)

Link Access Procedure (LAP) ProtocolsThere are three types of Link Access Procedure (LAP) protocols

Link Access Procedure Balanced (LAPB): An HDLC implementation that uses balanced asynchronous mode with error recovery to form the basis of the X.25 packet switching protocol

Link Access Protocol over D-channel (LAPD): It uses either the basic or extended asynchronous “balanced” mode configuration and provides the basis for both ISDN and frame relay services

LAPF: Same as aboveISDN and frame relay protocols and standards span the first three

layers of the OSIRM: Physical, data link, and networkRefer to Figure 7.17 (p. 251

Point-Point Protocol (PPP) and Serial Line Interface Protocol (SLIP)

It was developed for serial-line communications between routers, often multiprotocol routers of different vendor origins.

It has supeseded the older SLIP protocolPPP can support the configuration and management of links

between multiple multiprotocol routers via a serial interface in both synchronous and asynchronous mode

PPP could be used on any leased line between any two routersIt security features allow the network to check and confirm the

identity of users attempting establish a connection

Point-Point Protocol (PPP) and Serial Line Interface Protocol (SLIP) (Continue…)

It discards any packets received in error, letting the higher-level protocols sort out the retransmission.

IT can be shared with other serial-line protocols only on a session by session basis.

PPP has been adopted by hub and router vendors alike and is often the protocol of choice for remote-switched access.

LLC and MAC Sublayer ProtocolsTogether with the physical layer, data link standards make up the

core IEEE 802.X protocol standards.Refer to Figure 7.18 (p. 254)The MAC layer manages communications across the physical

medium, defines frame assembling and disassembling, and performs error detection and addressing functions

The LLC layer interfaces with the network layer through Service Access Points (SAPs)

Refer to Figure 7.19 (p. 254)Multiple MAC protocols can exist under the same LLCRefer to Figure 7.20 (p. 255)

Logical Link Control (LLC) SublayerThe LLC protocols are designed for peer-to-peer

communications over multipoint bus and ring topologies.The LLC allows a 802, .4, or .5 protocol to carry multiple,

logical sub-network traffic of each protocol over the same physical medium, such as the LAN

Two major modes of service interfacingConnection-oriented:

uses SAP peer-to-peer connection with flow control and error recovery

Connectionlessclass 1: unacknowledged connectionlessclass 2: acknowledged connectionless

Logical Link Control (LLC) Sublayer (Continue…)

Refer to Figure 7.21 (p. 265)When the logical data link layer receives user data in the

form of an information field, it adds a header to this field and forms what is called a Protocol Data Unit (PDU)

Refer to Figure 7.22 (p. 256)The PDU header contains both a destination address

and a source address of the origination port for a network hardware device or application for network software.

Both are referred to as Service Access Points (SAPs)

Media Access Control (MAC) SublayerThe MAC sublayer manages and controls

communications across the physical media, manages the frame assembling and disassembling, and performs error detection and addressing functions.

There is also one MAC layer bridge protocol 802.1d bridge (Spanning Tree) designed to interface any 802 LAN with any other 802 LAN.

When the MAC layer receives the LLC PDU, it adds a header and trailer for transmission across the MAC layer (and physical medium)

Refer to Figure 7.23 (p. 258)MAC addresses are unique and identify physical station points on the network

Media Access Control (MAC) Sublayer (Continue…)

The LLC header has been extended to allow more than 64 SAP values to be identified.

Also, two more field were added to the MAC frame format - an Organizationally Unique Identifier (OUI) for defining an organization that will assign a Protocol Identifier (PID) for the type of Ethernet

Refer to Figure 7.24 (p. 259)

802.3 CSMA/CD (Ethernet)Uses Carrier Sense Multiple Access with Collision Detection

(CSMA/CD) within a standard Ethernet frame, across a common physical medium bus with channel-attached MAC addressed stations

Theoretically it can send at rates reaching 10MbpsMaximum size of 802.3 frame is 1500 bytesCSMA/CD allows for stations to both transmit and receive data in a

“best-effort” data delivery system-no guarantee of data delivery is made

During a collision the end stations initiate a “back-off” algorithm and follow a mathematical formula to randomize each station’s next attempt to retransmit.

The medium can be either basedband or broadbandRefer to Figure 7.25 (p. 260)

802.4 Token BusA logical ring is formed on the physical bus, and each station knows

only the preceding station on the bus.A token is passed down the bus, from station to station in logical

ring sequence and by descending station addressRefer to Figure 7.26 (p. 261)Refer to Figure 7.27 (p. 261)

802.3 Token Ring A token circulates around the physical “hub” and logical “ring” topology and provides “priority access” to the network medium. The token is either free or busy.At heavy load conditions, the Token Ring protocol is much more bandwidth efficient than other LAN protocols The maximum frame size for a Token frame using the 4 Mbps medium is 4,000 bytes and for the 16 Mbps medium is 17,800 bytesRefer to Figure 7.28 (p. 262)Refer to Figure 7.29 (p. 263)

Fiber Distributed Data Interface (FDDI)It was designed to provide either a high-performance LAN

or a campus backbone.Shared FDDI MANs can be connected via DS3 or OC-3

SONET pipes to form a wider area network, subject to distance constraints.

FDDI operates over both physical- and MAC-layer protocols, providing a 100 Mbps transmission over a dual, counter-rotating optical fiber ring between nodes.

Up to 500 dual-attachment connection devices can interface to the FDDI ring in series.

FDDI ring supports a maximum of up to 1000 stations, with a maximum distance between stations of 2 km and a maximum ring total circumference of 100 to 200 km

Fiber Distributed Data Interface (FDDI) (Continue…)

FDDI operation is very similar to Token Ring protocolFDDI defines a Physical Medium Dependent (PMD) layer for

single or multimode operation through full-duplex connectors, optical tranceivers, and optional bypass switches.

The physical layer of FDDI consists of a class A dual attachment physical interface via the PMD sublayer.

Refer to Figure 7.30 (p. 264)The information field (data packet) ranges from 128 to 4500 bytes

whereas the maximum frame length is 9000 bytesRefer to Figure 7.31 (p. 265)

Fiber Distributed Data Interface (FDDI) (Continue…)

Basic operation is similar to Token Ring with the exception that each idle station on the ring has a chance to seize a passing free token

Refer to Figure 7.32 (p. 266)Two classes of stations use the FDDI ring

Class A : utilize both the inner and outer fiber rings. Also called Dual Attachment Stations (DAS)

Class B : cannot provide reroute, and use only the outer ring. They are Signle Attachment Stations (SASs)

Refer to Figure 7.33 (p. 267)

Fiber Distributed Data Interface (FDDI) (Continue…)During a link failure all class A stations can automatically

reconfigure to use the secondary ring. This capability is called self-healing

Class B stations will be offline because the primary ring they use is inactive during a failure condition.

Any station on the link can be taken down without affecting the FDDI ring.

Refer to Figure 7.34 (p. 267)

Fiber Distributed Data Interface (FDDI) (Continue…)

FDDI can be implemented with either single mode o rmultimode fiber-optic cable

FDDI can be transmitted over shielded and unshielded twisted-pair distances up to about 100 m.

WAN attachment is accomplished through both encapsulating and translating dual-attached bridges

Refer to Figure 7.35 (p. 268)Refer to Advantages and Disadvantages of FDDI LAN on page

269

FDDI-IIThe FDDI-II protocol structure will allow FDDI LANs to

transport multiplexed asynchronous packet data and isochronous circuit-switched data

A hybrid multiplexer layer has been added between the physical and MAC sublayer and frames are now called cycles.

Multiple 6 Mbps portions of data can be dynamically allocated to DS1 channels to support voice, data, and video.

This 6 Mbps consists of multiple 64 kbps channels. Each cycle can carry up to 16 channels, and each channel up to 6.144 Mbps.

FDDI-II (Continue…)This service is good for interconnection of PBX equipment to the

LAN and WAN, and combines telecommunications and data communications mixed media on the same fiber.

To date, the deployment of FDDI-II has been stalled by the lack of a vendor to produce a chipset and the offering of low-speed LAN ATM interface cards

FDDI contains some distance limitations

100-Mbps Ethernet: 100BASET and 100VG-AnyLAN

100BASE-T Fast EthernetIt speeds up the existing CSMA/CD media access control

mechanism to 100 Mbps100BaseT is an IEEE 802.3 standard and offers three major

segment types:T4: uses four-pair twisted wiringTX: uses two-pair twisted mediaFX: uses two-strand fiber-optic cable

100VG-AnyLANIt is called VG, Fast Ethernet, Fast Toekn Ring, and

Demand PriorityThe IEEE standard for 100VG-AnyLAN is 802.12, while

100BASEVG is 802.11 standard100VG-AnyLAN can operate over four-pair UTP (up to

100 m), two-pair STP (up to 200 m), and fiber-optic cable (up to 2000 m).

A deterministic demand priority scheme is used to create a predictable order by which nodes share the network.

100BASET is best used as an upgrade to existing 10 Mbps Ethernet when cabling permits but continued interoperability is required

Cisco

Configuration & IOS Management Commands

ObjectivesUse the setup feature on a Cisco routerLog into a router in both user and privileged modesFind commands by using the help facilitiesUse command on a router by using the editing commandSet the router passwords, identification, and bannersConfigure an interface with IP addresses and subnet

masksCopy the configuration to NVRAM

Cisco Router User Interface

Cisco Router IOS

Connecting to a Cisco Router

Bringing up a Router

2501 Router

Bringing up a RouterBoot-up process:

#1: POST#2: Looks for the Cisco IOS from Flash memory#3: IOS loads & looks for a valid configuration;

startup-configstartup-configstored in nonvolatile RAM (NVRAM)

#4: If a valid config is not found in NVRAM:setup modesetup mode

Setup Mode

Basic Management Setup

Extended Setup

Command-Line Interface

Logging into the RouterUser mode:

Router>Used mostly to view statistics

Privileged mode:Router#Used to view & change router configuration

Overview of Router ModesGlobal changes:

config terminal or config tChanges made to running-config running-config (DRAM)To change the startup-configstartup-config (NVRAM)

config memory or config mem

Note: Any configuration changes need to be placed into RAM. Typing config mem or config net (from a TFTP host) will replace the current running-configrunning-config

Configuration

CLI PromptsInterfacesSub-interfacesLine CommandsRouting Protocol Configurations

Editing & Help Features

Editing & Help FeaturesCommands starting with a certain letter

Router#c?clear clock configure connect copy

Enhanced Editing CommandsRouter-Command HistoryGathering Basic Routing Information

show versionshow version

Setting the Passwords5 passwords:

1st two used to set your enable passwordUsed to secure privileged mode; Router>enable

Other three are used to configure a password in useruser mode via:

console portauxiliary portTelnet

PasswordsEnable passwords

Router(config)#enable password ciscoRouter(config)#enable secret cisco

Auxiliary PasswordConsole PasswordTelnet PasswordEncrypting Your Password

Router(config)#service password-encryption

BannersPurposeTypes

execincomingloginmotd

Delimiting character

Router InterfacesPurposeBringing up an Interface

no shutdownshutdownshow interface

Configuring an IP Address on an InterfaceRouter(config)#int e0Router(config-if)#ip address 172.16.10.2 255.255.255.0Router(config-if)#no shut

Serial Interface Commandsclock rate & bandwidth (entered in kilobits)

Hostnames & DescriptionsHostnames

Router(config)#hostname toddtodd(config)#

DescriptionsAtlanta(config)#int e0Atlanta(config-if)#description Sales Lan

Viewing, & Saving Configurations

Viewing & Saving Configurationsrunning-configrunning-config saved in DRAMstartup-configstartup-config saved in NVRAM

copy run startsh runsh starterase startup-config

Verifying Your Configuration

Tools:show running-configshow startup-configpingshow cdp nei detailtracetelnetsh interface

sh int e0 sh int s1 (line up/down protocol up/down)

sh controllers

SummaryUsed the setup feature on a Cisco routerLogged into a router in both user and privileged modesFound commands by using the help facilitiesUsed command on a router by using the editing

commandSet the router passwords, identification, and bannersConfigured an interface with IP addresses and subnet

masksCopied the configuration to NVRAM