ACN networking questions

7/28/2019 ACN networking questions

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IEEE 802.2

o IEEE 802.2 LLC (Logical Link Control)

o It is the media access control sublayer dependent on the particular medium beingused

o Provides two connectionless and one connection oriented operational modeso Type 1:unacknowledged connectionless modeo Type 2:connection-oriented operational modeo Type 3:acknowledged connectionless service

Frame format

MAC HEADER IEEE 802.2 LLC DATA ::: CRC

o Data.:This field contains the encapsulated protocol.

o CRC, Cycle Redundancy Check.:4 bytes. Error checking.

o IEEE 802.3


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o In IEEE 802.3 Ethernet Data link layer is split into two sublayers:

o Bottom part: MAC

o The frame is called IEEE 802.3

o Handles framing, MAC addressing, Medium Access control

o

Specific implementation for each LAN protocol

ETHERNET STANDARDS

o 802.3(10mbps)

Char 10 base 5 10 base 2 10 base T 10 base F

Media Thick coaxial

cable

Thin coaxial cable Star UTP Star fiber

Max

length

500m 200m 100m 2000m

LES Manchester

LES

Manchester

LES

Manchester

LES

Manchester

LES

Speed 10 mbps 10 mbps 10 mbps 10 mbps

o Fast Ethernet(100mbps)

Characterstics 100 base tx 100 base fx 100 base t4

Media 2 wires cat 5 utp 2 wires fiber 4 wires cat 3 utp

No of wires 2 2 4

Max Length 100m 100m 100m

BES 4b/5b 4b/5b -

LES MLT-3 NRZ-I 8B/6T

Speed 100mbps 100mbps 100mbps


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IEEE 802.4(token bus)

o Token Bus (IEEE 802.4) combines features of Ethernet (a bus topology) and Token ring.

o Token bus is a physical bus that operates as a logical ring using tokens.

o Stations are logically organized into a ring. A token is passed among the stations. If a

station wants to send data, it must wait and capture the token.

o Token Bus is limited to factory automation and process control and has no commercial

applications in data communication

IEEE 802.5

Access Method: Token passing

o Whenever the network is unoccupied, it circulates a simple three-byte token.

o This token is passed from NIC to NIC in sequence until it encounters a station with data

to send.

o That station waits for the token to enter its network board. If the token is free the

station may send a data frame.

o This data frame proceeds around the ring regenerated by each station.


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IEEE 802.6(DQDB)

o Distributed Queue Dual Bus (DQDB)o DQDB is a MAN.

o

o Topology: Dual Bus

o Head-ends generate cells in both directions

o To transmit, a host must know whether the destination is to its right or its left

If right, the host must send on one bus

If left, the host must send on the other bus

o A Distributed Queue is used to make sure thatcells are transmitted on a first-come first-serve basis

DQDB Frame Format

o 53-byte frame called a cell


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o Difference between Wi-Fi and Wi-max

Wi-Fi Wi-max

usage o The Wi-Fi technology is

still using local areanetwork(LAN) for the

predictable future

o Wi-MAX stands for Worldwide

Interoperability for Microwave Access for

transmitting radio frequencies

IEEE o IEEE 802.11 o IEEE 802.16

Scalability o Fixed channel size

o 20 MHzo Flexible channel size

o 1.5 MHz to 20 MHz

Bit rate o 2.7 bps/Hz o

5bps/Hz

FIDDI

o Fiber distributed data interface.

o Token passing ring network that operates 100mb/s

o Have added features comparison to 802.4(Token Bus).o FDDI divides transmission function into 4 protocols:

Media Access Control (MAC): The MAC specification defines how themedium is accessed, including frame format, token handling, addressing,

algorithms for calculating cyclic redundancy check (CRC) value, and error-

recovery mechanisms

Physical Layer Protocol (PHY): The PHY specification defines dataencoding/decoding procedures, clocking requirements, and framing, among

other functions

Physical-Medium Dependent (PMD): The PMD specification defines thecharacteristics of the transmission medium, including fiber-optic links, power

levels, bit-error rates, optical components, and connectors.

Station Management (SMT):The SMT specification defines FDDI stationconfiguration, ring configuration, and ring control features, including station

insertion and removal, initialization, fault isolation and recovery, scheduling,

and statistics collection.


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o A Concentrator Attaches to Both the Primary and Secondary Rings

FRAME FORMAT


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HIPPIo High performance parallel interfaceo HIPPI is a very high-speed data transfer protocol, with the following properties, features,

and limitations:o Data rates of 800 or 1600 Mb/s.o Uses a 50- or 100-pair connection. (50-pair for 800 Mb/s data-rate, 100-pair for 1600 Mb/s

data rate.) The 100-pair connection is actually a set of two identical 50-pair cables.

o Useful for distances up to 25 meters. (Serial-HIPPI extensions are being proposed foroperation up to 10km.)

o Transfers 32 bits (for 800 Mb/s data-rate) or 64 bits (for 1600 Mb/s data-rate) in parallel.Packet format allows byte alignment.

o Connection-oriented protocol.o Point-to-point connection.o Simplex (i.e., one-way data transfer) operation.o First standard in its class (data-transfer for high-performance computing environments).o Designed for ease of implementation: available options are very limited.


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7 layers HIPPI:

o HIPPI-PH (Physical Layer) The HIPPI-PH standard defines the mechanical, electrical, and signaling of the

HIPPI physical layer

HIPPI is a simplex protocol, a full-duplex link would be achieved by another HIPPIconnection in the opposite direction.

HIPPI's physical layer consists of a set of 50-twisted-pair copper cables (maximumlength of 25 meters).

Signal Lines REQUEST(S-->D) CONNECT(D-->S) READY(D-->S) PACKET(S-->D) DATA BUS(S-->D) PARITY BUS(S-->D)

o HIPPI-FP (Framing Protocol) This standard describes the format and content (including header) of each packet

of user information. Other layers may be implemented above this one. Note also that this is the layer

which splits higher layer packets to the 1 or 2 K-byte packets required by the physical layer.

o HIPPI-SC (Switch Control) HIPPI-PH supports only a single point-to-point connection To Overcome, HIPPI-SC was developed as one workable solution to this

quandary. It allows for a switching mechanism to be built which could allow

multiple simultaneous point-to-point connections to occur

o HIPPI-LE(Link Encapsulation) provides mapping of IEEE 802.2 LLC headers to theD1_Area and the beginning of the D2_Area .

o HIPPI-FC(Fibre Channel) maps Fibre Channel products to the HIPPI-FP standard.

o HIPPI-IPI(Disk & Tape Commands) maps IPI-x standard command-sets into HIPPI-FP headers.

SONETo Synchronous Optical Network

o Synchronous optical network (SONET) is a standard for optical telecommunications

transport

o Standard for connecting fiber systems together


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o increased configuration flexibility and bandwidth availability provides advantages over the

older telecommunications system.

o Defines a fiber based transmission scheme for ATM

o A synchronized frame structure for multiplexing digital traffic

o

Procedures for operation and maintainance.o Frame format


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QUESTIONS:

Link local address

o A link-local address is required on each physical interface. Link-local addresses are designed

to be used for addressing on a single link for purposes such as automatic address

configuration, neighbor discovery, or in the absence of routers. It also may be used to

communicate with other nodes on the same link. A link-local address is automatically

assigned.

o Format

Site local Address

Site-local addresses are designed to be used for addressing inside of a site without the need for a

global prefix. A site-local address cannot be reached from another site. A site-local address is not

automatically assigned to a node. It must be assigned using automatic or manual configuration.

Global unicast address

o The global routing prefix is a (typically hierarchically-structured) value assigned to asite (a cluster of subnets/links). The subnet ID is an identifier of a link within the site.

The interface ID is used to identify an interface on a link; interface IDs are required to

be unique within a subnet prefix.

o All global unicast addresses other than those that start with B'000' have a 64-bitinterface ID field (that is, n + m = 64). Global unicast addresses that start

with B'000' have no such constraint on the size or structure of the interface ID field.o Examples of global unicast addresses that start with B'000' are IPv6 address with

embedded IPv4 addresses. These include IPv4-mapped IPv6 addresses and IPv4-

compatible IPv6 addresses.

o


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ADSL

o Asymmetric digital subscriber line uses existing twisted pair telephone lines to create

access paths for high-speed data communications and transmits at speeds up to

8.1Mbps to a subscriber. The "asymmetric" in ADSL refers to the fact that the

downstream data rate, or the data coming to your computer from the Internet, is

traveling faster than upstream data, or the data traveling from your computer to the

Internet

o ADSL CONFIGURATION

o ADSL types

Videostream (for video on demand, providing guarantee bandwidth)

DataStream An ATM product provided without an IP layer, used for corporate linkingtypically

IPStream which is the service that most domestic and business users will use in theUK.

Auto Configuration

o Auto configuration is an incredibly useful solution because it allows devices on a

network to address themselves with a link-local unicast addresso There are three types of auto configuration:

Stateless Configuration of addresses and other settings is based on the

receipt of Router Advertisement messages. These messages have the ManagedAddress Configuration and Other Stateful Configuration flags set to 0, and they

include one or more Prefix Information options, each with its Autonomous flag

set to 1.

Stateful Configuration is based on the use of an address configurationprotocol, such as DHCPv6, to obtain addresses and other configuration

settings. A host uses stateful auto configuration when it receives a Router

Advertisement message with no Prefix Information options and either the


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Managed Address Configuration flag or the Other Stateful Configuration flag is

set to 1. A host can also use stateful auto configuration when there are no

routers present on the local link.

Both Configurations is based on the receipt of Router Advertisementmessages that include Prefix Information options, each with its Autonomous

flag set to 1, and have the Managed Address Configuration or Other StatefulConfiguration flags set to 1. For all types of auto configuration, a link-local

address is always configured automatically.

Encryption and authentication in IPv6

Authentication in IPv6

o Extension Header type 51 provides integrity and authentication for end to end data

Types

1. Payload Authentication

Transport mode authenticates all end to end payload plus selected headers

(described previously)

Payload Length

Next Header

Extension headers

Upper layer headers and data

Will not work with NAT environment

2. Header and Payload Authentication


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Encryption in Ipv6

o Extension Header type 50 provides integrity and confidentiality

Types:


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IPv6

o Larger Address Space

o Aggregation-based address hierarchy

Efficient backbone routing

o Efficient and Extensible IP datagram

o Stateless Address Auto configuration

o Security (IPsec mandatory)

o Mobility

o 128-bit IPv6 Address

3FFE:085B:1F1F:0000:0000:0000:00A9:1234

8 groups of 16-bit hexadecimal numbers separated by :

Leading zeros can be removed

3FFE:85B:1F1F::A9:1234

:: = all zeros in one or more group of 16-bit hexadecimal numbers

o No option field: Replaced by extension header. Result in a fixed length, 40-byte IP

header.

o No header checksum: Result in fast processing.o No fragmentation at intermediate nodes: Result in fast IP forwarding.


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Difference between IPv4 and IPv6

IPV4 IPV6

o Ipv4 is 32 bit addressing (2 ^32)

o Features Use of Binary Format

0 countable

Limited Space

o 4 Octet of 8 bit each

X.X.X.X=8*4=32

o Support upto 232 addresses

o Router task is complex

o Smaller payload

o Header includes a checksum

o Manual Configuration

o IPsec is optional and should be

supported externally

o Ipv6 has addressing format(2 ^128).

o Features Use of hexadecimal Format

0 Uncountable

Unlimited Space

o 8 Octet of 16 bit each

XX.XX.XX.XX=8*16=128 bits

o Support upto 2128 Addresses

o Router task is easy

o Bigger payload

o Header does not includes a checksum

o Auto Configuration

o IPsec support is not optional

Source address (128 bits)

o The 128-bit source address field contains the IPv6 address of the originating node

of the packet. It is the address of the originator of the IPv6 packet.

Destination address (128 bits)

o The 128-bit contains the destination address of the recipient node of the IPv6

packet. It is the address of the intended recipient of the IPv6 packet.

Version/IP version (4-bits)

o The 4-bit version field contains the number 6. It indicates the version of the IPv6

protocol.


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Packet priority/Traffic class (8 bits)

o The 8-bit Priority field in the IPv6 header can assume different values to enable the

source node to differentiate between the packets generated by it by associating

different delivery priorities to them.

Flow Label/QoS management (20 bits)

o The 20-bit flow label field in the IPv6 header can be used by a source to label a set

of packets belonging to the same flow. A flow is uniquely identified by the

combination of the source address and of a non-zero Flow label. The IPv6 routers

must handle the packets belonging to the same flow in a similar fashion.

Payload length in bytes(16 bits)

o The 16-bit payload length field contains the length of the data field in octets/bitsfollowing the IPv6 packet header. The 16-bit Payload length field puts an upper

limit on the maximum packet payload to 64 kilobytes. In case a higher packet

payload is required, a Jumbo payload extension header is provided in the IPv6

protocol.

Next Header (8 bits)

o The 8-bit Next Header field identifies the type of header immediately following the

IPv6 header and located at the beginning of the data field (payload) of the IPv6

packet. This field usually specifies the transport layer protocol used by a packet's

payload.

Time To Live (TTL)/Hop Limit (8 bits)

o The 8-bit Hop Limit field is decremented by one, by each node (typically a router)

that forwards a packet. If the Hop Limit field is decremented to zero, the packet is

discarded

Hidden vs exposed node problem

o

In the case of hidden terminal problem, unsuccessful transmissions result fromcollisions between a transmission originated by a node such as A which cannot hearthe on going transmissions to its corresponding node B.

o In the case of exposed terminal, unsuccessfultransmissions result from nodes such asA being prevented from transmitting, because their corresponding node is unable to

send a CTS(clear to send)


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FDDI Pros AND Cons

FDDI Advantages

~Supports real time allocation of network bandwidth.

~Supports a lot of different types of network traffic.

~Is fault-tolerant because it uses dual fiber cables. If one cable fails FDDI moves the data to

the other dual cable.

FDDI Disadvantages:

~It's expensive

~There is always a chance of multiple ring failures and as the ring grows, that chance

increases.

~It's not used frequently due to cost, companies prefer to use copper (CDDI) if they are

taking the ring approach.

ATM

Asynchronous Transfer Mode

o It is a high speed, connection oriented switching and multiplexing technologycapable of transmitting voice, video and data and interconnecting LANs

o ATM is asynchronous because information streams can be sent independentlywithout the need of a common clock

Features Convergence of Voice , Video and Data on one network High speed switching at hardware level Bandwidth on demand Predefined and guaranteed QoS and CoS

Superior Management features Scalability in network size and speed Ease of integration with other technologies CoS is the classification of specific traffic (at layer 2) by manipulating the class of service bits QoS can use this identification/classification as a means to actually manipulate the traffic

according to your policy


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o Virtual Channel (VC) provides a fixed pathway or route between 2 points. Setup across an

ATM network whenever data transfer begins.o Virtual Path (VP)groups of VCs used to tell a switch how to forward an ATM cell through

an ATM network

o Virtual Path Identifier (VPI) in the ATM header used to identify route established in theATM Switch

o Virtual Channel Identifier (VCI) - in the ATM header used to identify a channel within a VPo Transmission path physical media transporting the cellso User to Network Interface (UNI) : Connection existing between the user equipment and

ATM equipment

o Virtual path Connection (VPC) connection from source end user VPI to the destinationend user VPI

o Operation : Cell is received across a link on a known VPI or VCI value - their values areremapped as necessary as all VCIs and VPIs are only significant to the local link


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o Two types of services are1) PVC

2) SVC

o PVC: Permanent Virtual Circuits allows direct connectivity between sites. In thisway, a PVC is similar to a leased line.

o SVC: Switched Virtual Circuits is created and released dynamically and remains inuse only as long as data is being transferred. In this sense, it is similar to a telephone

call.

If the maximum effective bandwidth at which TCP is able to transmit over aparticular path is B bytes per second, then the following constraint must be

satisfied for error-free operation:

o

2**31 / B > MSL (secs)

MOBILE IPV6

o Mobile IPv6 is intended to enable IPv6 nodes to move from one IP subnet to anothero While a mobile node is away from home, It sends information about its current

location to a home agent, The home agent intercepts packets addressed to the

mobile node and tunnels them to the mobile nodes present location

FEATURES

Address Auto configuration Stateless auto configuration

Network Prefix + Interface ID

Stateful auto configuration DHCPv6

Neighbor Discovery Discover each others presence and find routers

Determine each others link-layer addresses Maintain reachability information


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Route Optimizationo Route Optimization (RO) is standard in Mobile IPv6 (MIPv6) to route packets

between Mobile Node (MN) and Correspondent Node (CN) using shortest

possible path. It provides better bandwidth and faster transmission. RO greatly

increases the security risk.

One-way hash function

A one-way hash function, also known as a message digest, fingerprint or compression function,

is a mathematical function which takes a variable-length input string and converts it into a fixed-length binary sequence. Furthermore, a one-way hash function is designed in such a way that itis hard to reverse the process, that is, to find a string that hashes to a given value (hence thename one-way.) A good hash function also makes it hard to find two strings that would producethe same hash value.

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