Lan-technology.ppt 534t55

K. Suresh Sub Divisional Engineer(DX) Telephones: +91-120-2728412(O) +91-120-2728434(O) +91-120-2728839(R) E-mail: [email protected]

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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LAN Topology

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Inter working Devices Local Area Network (LAN) Works in a single office, building or campus Most common LAN topologies are bus, ring & star Ethernet was early network introduced in 1980

Wide Area Network (WAN) Provides long distance transmission over large geographical area

Metropolitan Area Network (MAN) Connecting number of LANs into a larger network using WAN circuits ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Network Topologies (Mesh & Star) Topology is the geometric representation of all the links and linking devices Dedicated point-topoint link between devices. Advantages: Dedicated link & fault isolation is easy Disadvantages: More Space/Hardware requirement

• Each device has a dedicated point-to-point link to a central controller, called a hub. • Advantages :Less expensive, fault isolation is easy & each device needs only one link • Disadvantage : If hub fails, whole network will be down

HUB

Mesh Topology ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

Star Topology 4

Network Topologies (Tree & Bus) Tree Topology The central hub in the tree is an active hub. An active hub contains a repeater. The secondary hubs can be active or ive.

HUB

HUB

HUB

Bus Topology Drop line Cable End

Tap

Drop line Tap

Drop line Tap

Drop line Tap

Cable End

 Advantages : Multi point, Ease of installation & Uses less cables than mesh/star/tree topologies  Disadvantage: Difficult to add new devices & A fault in the bus cable stops all transmission000 ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Network Topologies (Ring & Hybrid) Each device is connected with the two devices on either side of it. Advantages: To add or delete a device, requires moving only two connections & Fault isolation is simplified Disadvantage : A break in ring can disable the entire network.

Ring Topology Star

Hybrid Topology • Mixed topology using Star/Mesh & Ring according to the need

HUB HUB

Star

Bus

Ring

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Inter-working Devices

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Inter-working Devices

Hub Bridges LAN Switches Routers Gateways

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Hub

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Hubs Hubs are essentially physical-layer repeaters: bits coming from one link go out all other links at the same rate no frame buffering no CSMA/CD at hub: adapters detect collisions twisted pair

hub

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Hubs The active central element of the star layout. When a single station transmits, the hub repeats the signal on the outgoing line to each station. Physically a star; logically a bus. Hubs can be cascaded in a hierarchical configuration. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Hubs Operating at the physical layer, hubs are very simple devices that all traffic in both directions between the LAN sections they link. They may connect different types of cable, but use the same data link and network protocol. Strictly speaking, hubs are not considered part of a backbone network, but are usually repeaters or amplifiers. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Hub/Switch uses Star topology Bus topology popular through mid 90s Now star topology prevails Connection choices: hub or switch

hub or switch

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Interconnecting with hubs Backbone hub interconnects LAN segments Extends max distance between nodes But individual segment collision domains become one large collision domain Can’t interconnect 10BaseT & 100BaseT hub

hub

hub

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hub

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Bridges

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Bridges Allow connections between LANs and to WANs Operates at Layer 2 (Data Link Layer) of OSI Used between networks using identical physical and link layer protocols Provide a number of advantages Reliability: Creates self-contained units Performance: Less contention Security: Not all data broadcast to all s Geography: Allows long-distance links ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Bridges

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Bridge Functions Read all frames from each network Accept frames from sender on one network that are addressed to a receiver on the other network Retransmit frames from sender using MAC protocol for receiver Must have some routing information stored in order to know which frames to ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Bridges If a bridge receives a packet with a destination address that is not in the address table, it forwards the packet to all networks or network segments except the one on which it was received. Bridges are a combination of both hardware and software, typically a “black box” that sits between the two networks, but can also be a computer with two NICs and special software. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Bridge Operation

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LAN Switch

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Switch: Forwarding switch

1

2

hub

3

hub

hub

How do determine onto which LAN segment to forward frame? Looks like a routing problem... ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Switch: Self learning A switch has a switch table Entry in switch table: (MAC Address, Interface, Time Stamp) stale entries in table dropped (TTL can be 60 min)

Switch learns which hosts can be reached through which interfaces when frame received, switch “learns” location of sender: incoming LAN segment records sender/location pair in switch table

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Switch: Filtering/Forwarding When switch receives a frame: Searches the switch table using MAC destination address If entry found for destination then forward the frame on interface indicated, if it has not come from the same segment Else drop the frame If no match found in the switch table, flood on all the other interfaces

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Switch example 1

B

C

A B E G

3

2

hub

hub

hub

A

address interface

switch

1 1 2 3

I D

E

F

G

H

Suppose C sends frame to D Switch receives frame from from C notes in bridge table that C is on interface 1 because D is not in table, switch forwards frame into interfaces 2 and 3

Frame received by D ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Switch example address interface

switch

B

C

hub

hub

hub

A

I D

E

F

G

A B E G C

1 1 2 3 1

H

Suppose D replies back with frame to C. Switch receives frame from D notes in bridge table that D is on interface 2 because C is in table, switch forwards frame only to interface 1

Frame received by C ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Switch: traffic isolation Switch filters packets: same-LAN-segment frames not usually forwarded onto other LAN segments segments become separate collision domains switch

collision domain hub

collision domain

hub

hub

collision domain

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Switches: dedicated access Switch with many interfaces Hosts have direct connection to switch No collisions; full duplex Switching: A-to-A’ and B-to-B’ simultaneously, no collisions

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A C’

B

switch

C B’

A’

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Switches Like bridges, switches operate at the data link layer. Switches connect two or more computers or network segments that use the same data link and network protocol. They may connect the same or different types of cable.

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Switches Switches operate at the same layers as bridges but differ from them in two ways: First, most switches enable all ports to be in use simultaneously, making them faster than bridges. Second, unlike bridges, switches don’t learn addresses, and need to have addresses defined.

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Ethernet Hubs and Switches Shared medium hubs

Switched LAN hubs

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x

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Switched Ethernet A simple concept behind switched Ethernet - replace the LAN hub with a switch. Each computer now has its own dedicated point-topoint circuit. By increasing the number of connections from the server to the switch, the throughput of the server will be improved because of more circuits. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Switched Ethernet

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Types of Switches Switch establishes a connection between two segments just long enough to send the current packet Incoming packets (part of an Ethernet frame) are saved to a temporary memory area (buffer) MAC address contained in the header is read and then compared to a list of addresses maintained in the switch's lookup table ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Types of Switches

Routes the packet using one of the following methods: Cut-through Store-and-forward Fragment-free ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Cut-through Switching After storing the MAC Address (6 bytes) immediately begin sending the packet to the destination node, even as the rest of the packet is coming into the switch. No CRC Checking (disadvantage) Fast switching (advantage)

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Store-and-forward Switching Switch will save the entire packet to the buffer and check it for CRC errors or other problems before sending. Otherwise, the switch looks up the MAC address and sends the packet on to the destination node. Slow (disadvantage) Error free operation (advantage)

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Fragment-free Switching Works like cut-through except that it stores the first 64 bytes of the packet before sending it on. The reason for this is that most errors, and all collisions, occur during the initial 64 bytes of a packet. Still CRC cannot be checked (disadvantage) faster (advantage)

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Layer 3 Switches Problems With Layer 2 Switches Broadcast overload because of the single MAC broadcast address (e.g. using ARP for Data Link Layer address resolution) Lack of multiple links - only one path

Normally, the above problems can be solved with several subnets connected by routers. However, A MAC broadcast frame is then limited to only the devices and switches contained in a single subnet. A router does all IP-level processing, some of which could be not necessary. It is implemented in software and slow.

Layer 3 switches implement the packet-forwarding logic of the router in hardware. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Transparent Bridging & Broadcast storm

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Transparent Bridging A Technology that allows a switch to learn everything it needs to know about the location of nodes on the network without the network having to do anything. Transparent bridging has five parts: Learning Flooding Filtering Forwarding Aging ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Transparent Bridging Switch A

Node A

Node C

H U B

Segment-A HUB

Switch C

Switch B Node B

Segment-B ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Transparent Bridging: Learning A computer (Node A) on the first segment (Segment A) sends data to a computer (Node B) on another segment (Segment B). The switch gets the first packet of data from Node A. It reads the MAC address and saves it to the lookup table for Segment A. The switch now knows where to find Node A anytime a packet is addressed to it. This process is called learning. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Transparent Bridging: Flooding Since the switch does not know where Node B is, it sends the packet to all of the segments except the one that it arrived on (Segment A). When a switch sends a packet out to all segments to find a specific node, it is called flooding.

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Transparent Bridging: Forwarding Node B gets the packet and sends a packet back to Node A in acknowledgement. The packet from Node B arrives at the switch. Now the switch can add the MAC address of Node B to the lookup table for Segment B. Since the switch already knows the address of Node A, it sends the packet directly to it. Because Node A is on a different segment than Node B, the switch must connect the two segments to send the packet. This is known as forwarding. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Transparent Bridging: Filtering The next packet from Node A to Node B arrives at the switch. The switch now has the address of Node B, too, so it forwards the packet directly to Node B. Node C sends information to the switch for Node A. The switch looks at the MAC address for Node C and adds it to the lookup table for Segment A. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Transparent Bridging: Filtering The switch already has the address for Node A and determines that both nodes are on the same segment, so it does not need to connect Segment A to another segment for the data to travel from Node C to Node A. Therefore, the switch will ignore packets traveling between nodes on the same segment. This is filtering. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Transparent Bridging: Aging Learning and flooding continue as the switch adds nodes to the lookup tables. Most switches have plenty of memory in a switch for maintaining the lookup tables; but to optimize the use of this memory, they still remove older information so that the switch doesn't waste time searching through stale addresses. To do this, switches use a technique called aging. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Broadcast Storms Node B

Switch A Segment-C

Segment-A

HUB

Switch C

Switch B Node A

Segment-B ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Broadcast Storms When switches are connected in a loop, a packet from a node could quite possibly come to a switch from two different segments. In this scenario, imagine that Node B is connected to Switch A, and needs to communicate with Node A on Segment B. Switch A does not know who the destination Node A is, so it floods the packet. Packet travels via Segment A or Segment C to the other two switches (B and C). ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Broadcast Storms Switch B will add Node B to the lookup table it maintains for Segment A, while Switch C will add it to the lookup table for Segment C. Each switch will take the packet sent by the other switch and flood it back out again immediately, since they still don't know who the destination Node A is. Switch A will receive the packet from each segment and flood it back out on the other segment. This causes a broadcast storm as the packets are broadcast, received and re-broadcasted by each switch. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Spanning Tree Protocol

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Spanning Tree Prevents broadcast storms Standardized as the 802.1d specification by IEEE. Spanning Tree uses the spanningtree algorithm (STA) that: senses that the switch has more than one way to communicate with a node determines which way is best and blocks out the other duplicate path(s) ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Spanning Tree Protocol Each switch is assigned a group of IDs, one for the switch itself and one for each port on the switch. The switch's identifier, called the bridge ID (BID), is 8 bytes long and contains a bridge priority (2 bytes) along with one of the switch's MAC addresses (6 bytes). Each port ID is 16 bits long with two parts: a 6-bit priority setting and a 10-bit port number. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Spanning Tree Protocol A path cost value is given to each port. The cost is typically based on a guideline established as part of 802.1d. According to the original specification, cost is 1,000 Mbps (1 gigabit per second) divided by the bandwidth of the segment connected to the port. Therefore, a 10 Mbps connection would have a cost of (1,000/10) 100.

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Spanning Tree Protocol Each switch begins a discovery process to choose which network paths it should use for each segment. This information is shared between all the switches by way of special network frames called bridge protocol data units (BPDU). The parts of a BPDU are:

Root BID - This is the BID of the current root bridge. Path cost to root bridge - This determines how far away the root bridge is. Sender BID - This is the BID of the switch that sends the BPDU. Port ID - This is the actual port on the switch that the BPDU was sent from.

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Spanning Tree Protocol All switches constantly send BPDUs to each other. When a switch receives a BPDU (from another switch): Checks if it is better than the one it is broadcasting for the same segment If yes, then it will stop broadcasting its BPDU out that segment It will store the other switch's BPDU for reference and for broadcasting out to inferior segments, such as those that are farther away from the root bridge ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Spanning Tree Protocol A root bridge is chosen based on the results of the BPDU process between the switches. Initially, every switch considers itself the root bridge. When a switch first powers up on the network, it sends out a BPDU with its own BID as the root BID. When the other switches receive the BPDU, they compare the BID to the one they already have stored as the root BID. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Spanning Tree Protocol If the new root BID has a lower value, they replace the saved one. If the saved root BID is lower, a BPDU is sent to the new switch with this BID as the root BID. When the new switch receives the BPDU, it realizes that it is not the root bridge and replaces the root BID in its table with the one it just received. The result is that the switch that has the lowest BID is elected by the other switches as the root bridge. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Spanning Tree Protocol Based on the location of the root bridge, the other switches determine which of their ports has the lowest path cost to the root bridge. These ports are called root ports, and each switch (other than the current root bridge) must have one. The switches determine who will have designated ports.

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Spanning Tree Protocol A designated port is the connection used to send and receive packets on a specific segment. By having only one designated port per segment, all looping issues are resolved. Once the designated port for a network segment has been chosen, any other ports that connect to that segment become non-designated ports. They block network traffic from taking that path so it can only access that segment through the designated port. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Routers & Gateways

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Routers Routers operate at the network layer. Routers connect two or more LANs that use the same or different data link protocols, but the same network protocol. Routers may be “black boxes,” computers with several NICs, or special network modules in computers. In general they perform more processing on each message than bridges and therefore operate more slowly. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Routers

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Routers

Ethernet switch

3rd floor

2nd floor

1st floor

router

Segments LANs into distinct networks and subnetworks; e.g. the distinct red, green and blue LANs with distinct network numbers.

Segments LANs into broadcast domains

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Routers

Provides interface to the WAN. Intranet, commercial Internet and Internet2 connections.

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Routers vs Bridges Routers can choose the best route. Routers also only process messages specifically addressed to it. Routers can connect networks using different data link layer protocols. Therefore, routers are able to change data link layer packets. Routers may split a message into several smaller messages for transmission. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Switches vs. Routers Both store-and-forward devices routers: network layer devices (examine network layer headers) switches are link layer devices

Routers maintain routing tables, implement routing algorithms Switches maintain switch tables, implement filtering, learning algorithms

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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LAN: Switches vs. Repeaters Repeaters (hubs) are old technology. A repeater sends (repeats) packets that are incoming on one port, out all other ports (I know you’re out there somewhere!). Can only operate in half duplex mode. Bandwidth and jitter provided to any single device is highly dependent on the LAN traffic.

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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LAN: Switches vs. Repeaters A switch learns the MAC addresses of the devices connected to it, and sends packets directly and only to the target end-point. Provides much more consistent bandwidth and latency (low jitter). A well-designed switched LAN is important for videoconferencing. Repeater-based LANs should be upgraded to switched for videoconferencing! ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Campus LAN example to external network

mail server web server

router

switch

IP subnet

hub

hub

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

hub

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Gateways Gateways operate at the network layer and use network layer addresses in processing messages. Gateways connect two or more LANs that use the same or different (usually different) data link and network protocols. The may connect the same or different kinds of cable. Gateways process only those messages explicitly addressed to them. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Gateways Gateways translate one network protocol into another, translate data formats, and open sessions between application programs, thus overcoming both hardware and software incompatibilities. A gateway may be a stand-alone microcomputer with several NICs and special software, a FEP connected to a mainframe computer, or even a special circuit card in the network server. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Gateways One of the most common uses of gateways is to enable LANs that use T/IP and ethernet to communicate with IBM mainframes that use SNA. The gateway provides both the basic system interconnection and the necessary translation between the protocols in both directions.

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Gateways

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Backbone Architecture

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Backbone Architecture Layers

Network designs are made up of three technology layers: The access layer which is the technology used in LANs The distribution layer connects LANs together The core layer connects different backbone networks together ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Backbone network design layers

LAN LAN LAN LAN LAN LAN

Core Layer ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

Distribution Layer

Access Layer 78

Routed Backbones Routed backbones move packets using network layer addresses Each LAN is a separate and isolated network. LANs can use different data link layer protocols. Main advantage: LAN segmentation.

Main disadvantages: Routers introduce more delay and require more mgmt. compared to bridging/ switching ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Routed Backbones

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Bridged Backbones Forwards the packet based on their data link layer addresses. The entire bridged backbone falls under one subnet. Bridged backbones are cheaper Performance performs well For small networks for large networks broadcast messages lower performance. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Bridged Backbones

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Collapsed Backbones Collapsed backbones use a star topology The backbone has fewer devices. Advantages are: simultaneous access and much higher performance a simpler & more easily managed network.

Disadvantages are: use more cable if the central switch fails, the network goes down. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Collapsed Backbones

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Rack-based Collapsed Backbones Rack-based backbones collapse the into a single room using Main Distribution Facility (MDF)

Devices are connected using short patch cables. Moving computers between LANs is relatively simple

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Rack-based Collapsed Backbones

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Chassis-based Collapsed Backbones

Uses a large chassis switch that has slots into which modules can be inserted. Chassis switch designs include a number of open slots and have an internal capacity capable of ing all active modules.

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Chassis-based Collapsed Backbones

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Ethernet Technology

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Background of Ethernet (First LAN) Digital, Intel & Xerox (DIX) consortium created original Ethernet 1980 (originally known as Alto Aloha Network) The first network to provide Carrier Sense Multiple Access / Collision Detection (CSMA/CD) Ethernet_II to followed in 1984 (ver-2) IEEE termed this as 802 project Initially IEEE 802 Project divided into three groups ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Initial IEEE 802 Project High level interface (HILI) became 802.1 committee Responsible for High level interworking protocols and management

LLC group became 802.2 committee, for end to end link connectivity between higher layer and media access dependent layers

DL & MAC (DLMAC) group became responsible medium access protocols DL MAC has been split into three sub committees ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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DL MAC committees – 802.3 802.3 for Ethernet Came of with Ethernet physical layer spec. MAC addressing is same as Ethernet_II but length field replaced type filed Bus topology LAN at 10 Mbps with collision detection (CSMA/CD) 10base 2/ thinnet – 185 meters segment without repeater over RG58 coaxial cable at 50 ohms 10base 5/ thicknet – 500 meters segment without repeater over RG8/11 coaxial cable at 50 ohms 10base T/UTP – cat 3 UTP(Unshielded Twisted Pair) to 10 Mbps ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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DL MAC committees – 802.4/802.5 802.4 for Token Bus Burroughs, concord data systems, Honeywell, western digital, general motors & Boeing took over 802.4 802.5 for Token Ring IBM worked on 802.5

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Ethernet Standards (802.3) Ethernet (10 Mbps)

Ethernet_II - (DIX- Ethernet) IEEE 802.3 - Ethernet

Fast Ethernet (100 Mbps) IEEE 802.12 - 100VG AnyLAN IEEE 802.3u - Fast Ethernet

Gigabit Ethernet (1000 Mbps or 1 Gbps) IEEE 802.3z - Gigabit Ethernet IEEE 802.ab - Gigabit Ethernet

10 Gigabit Ethernet (10 Gbps) IEEE 802.3ae - 10 Gigabit Ethernet

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Ethernet_II DIX-Ethernet Layers

Upper Layers

Other Layers

Network Media Access Control

Network Data Link

(MAC)

Physical

Ethernet_II

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OSI model

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Ethernet Frame Structure Sending Network Adapter encapsulates IP datagram (or other network layer protocol packet) in Ethernet frame

Preamble: 7 bytes with pattern 10101010 followed by one byte with pattern 10101011 Used to synchronize receiver, sender clock rates ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Ethernet Frame Structure Addresses:matching destination address or broadcast address are ed to network-layer protocol rest discarded Type: indicates the higher layer protocol CRC: checked at receiver, if error is detected, the frame is simply dropped

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Ethernet CSMA/CD algorithm Adaptor receives datagram from Layer3 & creates frame If adapter senses channel idle, it starts to transmit frame. If it senses channel busy, waits until channel idle and then transmits If adapter transmits entire frame without detecting another transmission, the adapter is done with frame !

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Ethernet CSMA/CD algorithm If adapter detects another transmission while transmitting, aborts and sends jam signal After aborting, adapter enters exponential backoff after mth collision first collision: choose K from {0,1} i.e.{0, 221}; delay is K x 512 bit transmission times after second collision: choose K from {0,1,2,3}…ie. {0,1,..22-1} after ten collisions, choose K from {0,1,2,3,4,…,1023}I.e. {0,1,..210-1}

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Ethernet_II- Frame

64~1518B

8B PREAMBLE

6B DESTINATION HARDWARE ADDRESS

72~1526B 6B SOURCE HARDWARE ADDRESS

2B

46~1500B

4B

T Y P E

LAYER 3 DATA

CRC

Eg. Of Type Fields:  0800- IP  0806- ARP  8035- RARP

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Ethernet_II Frame - Details Preamble: 8 bytes of alternating 0s and 1s to synchronise the receiver Destination Address (DA): 6 bytes (48 bits) unique physical address of destination machine encoded in NIC Source Address (SA): 6 bytes (48 bits) unique physical address of source machine encoded in NIC Type : 2 bytes (16 bits) indicates the type of Layer 3 protocol being used Eg. IP, ARP or RARP (uses RFC 1700 Ethernet Type Values) Layer 3 Data: Between 46-1500 bytes CRC : 4 bytes (32 bits) for error detection information ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004 101

MAC Address structure (for all Ethernet) Destination address : (LS Bit first and MS bit Last in each byte Little-Endian style)

I/G Individual / group address: 0 - Individual address. 1 - Group address. U/L Universal /local address: 0 - Universally istered. 1- Locally istered. Source address (LS Bit first and MS bit Last in each byte Little-Endian style) I/G bit is always 0. U/L Universal/local address may be 0/1 LSB

MSB LSB

MSB LSB

MSB LSB

MSB LSB

MSB LSB

MSB

U/L I/G Most Significant Byte

Least Significant Byte

Organisationally Unique Identifier (OUI)

Vendor Assingned No. (Serial No.)

(3 bytes)

(3 bytes)

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CSMA/CD Ethernet Uses Carrier Sense Multiple Access with Collision Detection (CSMA/CD) as access method Any station wishing to transmit must listen for Carrier on the line If no carrier is detected, the line is idle and transmission can be initiated Two or more stations transmits at the same time, when there was no carrier, results in collision which is indicated by high voltage on the line After collision retry is done at staggered time by different devices CSMA/CD reduces the number of collision but does not eliminate them ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Cabling Spec. for UTP Standard Category Category Category Category

3 4 5 6

– – – –

(Cat 3)for speed 10 Mbps (Cat 4) for speed 16 Mbps Cat 5) for speed 100 Mbps (Cat 6) for speed 1Gbps

also known as Category 5E

Category 7 – Cat 7) for speed 10 Gbps

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IEEE Project 802 IEEE Project 802 sets standard to enable interworking between devices of various vendors. Logical Link Control (LLC) sub-layer has been added to achieve the above objective Other Layers Network

Other Layers Network

Logical Link Control

Data Link

Media Access Control

Physical

IEEE Project 802

OSI model

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105

Initial IEEE Project 802 • IEEE 802.2 LLC deals with logical address, control information and data • MAC sub layer resolves contention for shared media Other Layers Network 802.2 - Logical Link Control 802.3 CSMA/CD

802.4 Token Bus

802.5 Token Ring

ANSI FDDI

IEEE Project 802 ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

106

802.3 MAC Frame/802.2 LLC without SNAP

DSAP

SSAP

1B

1B

Control 1–2 B

802.2 LLC LAYER ENCAPSULATION

DATA

3B

43~1497B

DESTINATIO

PREAMBLE

S N F HARDWARE D ADDRESS

7B

1B

6B

SOURCE HARDWARE ADDRESS

LE N GT H

802.2 PDU

CRC

6B

2B

46~1500B

4B

64~1518B 72~1526B ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

107

802.3 MAC Frame Preamble 7 bytes of alternating 0s and 1s that alert the receiving system and enable it to synchronise its input timing

Start Frame Delimiter (SFD) I byte (10101011) signals the beginning of the frame

Destination Address (DA) 6 bytes (48 bits) unique physical address of destination machine encoded in NIC

Source Address (SA) 6 bytes (48 bits) unique physical address of source machine encoded in NIC ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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802.3 MAC Frame Length (2 bytes) Indicate number of bytes in the frame

802.2 PDU Upper layer information between 46-1500 bytes

CRC (4 bytes) for error detection information

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109

802.2 LLC Header DSAP:Destination service access point structure I/G - Individual/group address 0 - Individual DSAP. 1 - Group DSAP. SSAP:Source service access point structure C/R - Command/response: 0 - Command. 1 - Response. Control: The structure of the control field is same as HDLC . For IP Network value is (03) I/G

DSAP

C/R

SSAP

Control

802.2 LLC Header ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

110

802.3 MAC Frame/802.2 LLC with SNAP OUI- Organisationally Unique Identifier

OUI

Ether Type

3B

2B

SNAP- Sub Network Access Point

DSAP

SSAP

1B

1B

802.2 LLC / SNAP ENCAPSULATION

S N F HARDWARE D ADDRESS

1B

1–2 B

5B

38~1492B

DESTINATIO

7B

SNAP

DATA

8B

PREAMBLE

Control

6B

SOURCE HARDWARE ADDRESS

LE N GT H

802.2 PDU

CRC

6B

2B

46~1500B

4B

64~1518B 72~1526B ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Ethernet Encapsulations Methods

On Ethernet you have four encapsulation formats: Ethernet version II Novell-specific framing Ethernet 802.3/802.2 without SNAP Ethernet 802.3/802.2 with SNAP Ethernet 802.3/802.2 with SNAP ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

112

Ethernet Encapsulations Methods Ethernet 802.3/802.2 uses the type field to determine the packet protocol. 802.3/802.2 use the DSAP and SSAP fields. Because there are only 256 possible SAP values, they are fairly hard to get. The special SAP number of AA was assigned to indicate that there are further headers after the 802.2 header that must be seen to determine the network-level protocol. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

113

Ethernet Encapsulations Methods This is the SNAP (Sub Network Access point) header that uses the same type field used by Ethernet_II. IP on an Ethernet can be indicated by Ethernet V2 type 0x0800; 802.2 SAP code 0x06; or a SAP code of 0xAA followed by a SNAP type code of 0x0800. AppleTalk can be indicated by either Ethernet V2 type 0x809B (Phase I), or a SAP code of 0xAA followed by a SNAP type code of 0x809B (Phase II). AppleTalk is currently never sent as an 802.3/802.2 packet with a unique SAP code. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

114

Ethernet Encapsulations Methods Novell can be found as either Ethernet type 0x8137, or a raw 802.3 packet. It is not sent as an 802.3/802.2 packet with a unique SAP code (0xE0). There are only a few SAP values that you are likely to run across. They are: 04 - IBM SNA 06 - IP 80 - 3Com AA - SNAP BC - Banyan E0 - Novell (TR) ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

115

Ethernet (Cabling Spec.) Three main Cabling specifications are available in Ethernet: 10 Base 5 Uses Thick co-axial Cable

10 Base 2 Uses Thin Coaxial Cable

10 Base T Uses Unshielded Twisted pair cable ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

116

10Base5; Thick Ethernet; Thicknet The nickname derives from the size of the cable Each station on Ethernet network has its own Network Interface Card (NIC) which provides the station with a unique 6 bytes physical address Each frame is transmitted to every station on the link but will be read only by the station to which it is addressed Transceiver performs the CSMA/CD for checking voltages and collisions on the line ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

117

10Base5; Thick Ethernet; Thicknet R Segment 1

2.5 M

1

R

50 M

2

6

5

Segment 1

500 M; 200 Stations 4 5 Segments; 2500 M; 1000 Stations 1-NIC(Network Interface Card)

2-RG-8 Thick Coaxial Cable

3-Cable Terminator

4-Transceiver Vampire Tap

3

5-Attachment Unit Interface (AUI);Transceiver Cable (15 Wires) 6-Media Attachment unit (MAU);commonly known as Transceiver ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

118

10Base2; Thin Ethernet; Thinnet Also known as cheapnet or cheapernet Provides same data rate as 10Base5 but with distance limitation of 185 meters and lesser number of work stations Transceiver circuitry has moved into the NIC Transceiver tap has been replaced by a connector that splices the station directly into the cable BNC-T connector is with 3 ports; one for NIC, one each for input and output ends of the cable ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

119

10Base2; Thin Ethernet; Thinnet

3 1

2

4 185 M 1-NIC(Network Interface Card)

2-RG-58 Thin Coaxial Cable

3-BNC-T Connector

4-Cable Terminator

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120

10BaseT A star topology LAN All individual transceiver functions and networking operations are placed in an intelligent hub with a port for each station Hub fans out any transmitted frame to all its connected stations Frame will be read by all, but will only be processed by the station to which it is addressed ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

121

Manchester encoding

Used in 10BaseT Each bit has a transition Allows clocks in sending and receiving nodes to synchronize to each other ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

122

10BaseT

1 2

10Base-T Hub

5

3

100 M

4 100 M

1-10 Base-T Hub

2-RJ-45 Connector Male

3-RJ-45 Connector Female

4-Network Interface Card

5-RJ-45; Four Pairs UTP (Unshielded Twisted Pair) Cable

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

123

Fast Ethernet Standards Two standards are approved by IEEE in June 1995 802.12 802.3u

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

124

Fast Ethernet Standards- 802.12/802.3u 802.12 Uses even efficient signaling techniques than CSMA/CD known as Demand Priority Access Method (DPAM) Also known as 100VG-AnyLAN is similar to the other standard however utilizes a different type of Ethernet frame to send its data. Not popular and eventually disappeared from the market

802.3u Most popular spec. in 100Mbps over cat 5 UTP or cat 5 plus ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

125

Need for Media Independent Interface (MII) Fast Ethernet requires faster interface than 10 Mbps Ethernet 10 Mbps Ethernet uses Attachment Unit Interface (AUI) to connect Ethernet segment MAC is to remain constant for any physical layer technologies AUI cannot 100 Mbps Ethernet because of high frequencies( AUI Uses 2.5 MHz clock in Ethernet- 10 Mbps) 100 base T needed new interfacemedia Independent Interface (MII) ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

126

Media Independent Interface (MII)

100 base T created new Sub interface between physical/data link layer called reconciliation sub layer (RS) RS maps is 1s and 0s to MII. MII transfers one nibble which is 4 bits MII has 25MHz clock and and one nibble (4 bits) are transferred to Physical Layer every clock cycle

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

127

Fast Ethernet MII/Physical Layers

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

128

100 Base T (Cabling Spec.) 100Base-T is available in three different types of cable technologies: 100Base-T4 = Utilizes four pairs of telephonegrade twisted-pair wire and is used for networks that need a low quality twisted-pair on a 100-Mbps Ethernet 100Base-TX = Developed by ANSI 100BaseTX is also known as 100Base-X, 100Base-TX uses two wire data grade twisted-pair wire 100Base-FX = Developed by ANSI, 100BaseFX utilizes 2 stands of fiber cable ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

129

Fast Ethernet 100 Base-TX Uses 2 pairs (1 pair towards hub and other pair from hub) of CAT-5 UTP or STP Encoding used is 4B/5B Distance between hub & station be < 100 M

100 Base-FX Uses 2 optical Fibers (1 fibre towards hub and other fibre from hub) Encoding used is 4B/5B Distance between hub & station be < 2000 M ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

130

Fast Ethernet 100 Base-T4 Makes use of already exiting telephone cables Uses 4 pairs of voice grade UTP CAT-3 2 pairs are bi-directional and the other 2 are uni-directional At a time 3 pairs are used to carry data in each direction at a data rate of 33.33 Mbps i.e. 2 pairs carry data bi-directionally Encoding used is 8B/6T (8Binary/6Ternary) Distance between hub & station be < 100 M ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

131

Auto Negotiation in Fast Ethernet Auto negotiatiation uses a priority scheme to decide more preferred option for 100/10 Mbps Ethernet Lower the functioning value more the preferred one Auto negotiatiation uses fast link pulses (FLPs) for negotiatiation Lowest functioning option is chosen Auto negotiation may fail sometimes Important connection are configured manually ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

132

Auto Negotiation Priorities Standard 100 base T2 100 base T2 100 base Tx 100 base Tx 100 base T4 10 base T 10 base T

full/half full half full half half full half

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

Auto negotiation priority 1 2 3 4 5 6 7 133

10BaseT and 100BaseT 10/100 Mbps rate; latter called “fast ethernet” ‘T’ stands for Twisted Pair Nodes connect to a hub: “star topology”; 100 m max distance between nodes and hub

twisted pair

hub

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

134

Gigabit Eth MAC/Phy Layer 1000 base T created new Sub interface between physical/data link layer known as GMII ( Gigabit Media Independent Interface). GMII transfers one byte (8 bits) at a time to physical layer GMII has 125MHz clock and and one byte (8 bits) is transferred to Physical Layer every clock cycle ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

135

Gigabit Ethernet MAC/Phy Layer

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136

Gigabit Ethernet 4 implements have been designed: 1000 1000 1000 1000

Base-LX Base-SX Base-CX Base-T

FEATURE

1000Base-LX

1000Base-SX

1000BaseCX

1000Bas e-T

MEDIUM

Optical Fiber (Multi mode; Single mode)

Optical Fiber (Multi mode)

STP

UTP

SIGNAL

Long-Wave Laser

Short-Wave Laser

Electrical

Electrical

25M

25M

MAXIMU 550 Meters M Multi mode; 550 Meters DISTAN 5000 Meters ALTTC/CE DX Faculty/Single KSK/ LAN Technology/ Nov 2004 mode

137

Ethernet Cabling Spec for UTP

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

138

IEEE 802.4 (Token Bus)

T

Combines physical configuration of Ethernet (a bus topology) and the collision free feature of Token Ring Token bus is a physical bus that operates as logical ring using tokens (Round Robin) ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

139

IEEE 802.5 (Token Ring) Each transmits only one frame during its turn Access method is token ing Station keeps the token and sends the frame in the ring Each station in the ring regenerates the frame The intended recipient copies the frame and send the frame back to sender The sender receives the frame back, discards the frame and releases the token for others ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

140

Ring Topology & Token Ring Hub

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

141

Token Ring Media Access Control Token ring uses a controlled-access technique called token ing. The “token” is a series of bits, travels between the computers in a predetermined sequence. A computer with a message waits to transmit until it receives a free token. The computer changes the free token to a busy token and attaches its message to it. Then it retransmits it on the circuit to the next computer in the sequence. The computer receiving the message, changes the acknowledgement to ACK (or NAK) and sends the message back to the sender, who creates a new free token.

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142

Token Ring Media Access Control

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

143

Token Ring Media Access Control

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

144

Token Ring Media Access Control

Token loss: The token crashes before being transmitted - lost a free token A computer in the ring crashes - lost a busy token A token is always busy. A solution for the “lost” token problem: Designate one computer to be the token monitor and another computer to be a backup token monitor. If no token circulated through the network for a certain length of time or if a busy token circulates too often, the token monitor will create a new free token (and destroy the busy token if necessary.) ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

145

IEEE 802.5 (Token Ring)

T

T

T

T

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

146

FDDI Fiber Distributed Data Interface, standardised by ANSI and the ITU-T High speed alternative to Ethernet and Token Ring Copper version of FDDI is known as CDDI Uses Token ing as access method Implemented in dual ring In most cases, data transmission is confined to the primary ring The secondary ring is provided in case the primary ring fails ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

147

MAC Address structure- Token Ring/FDDI Destination address (LS Bit first and MS bit Lastin each byte Big-Endian style)

I/G Individual / group address 0 - Individual address. 1 - Group address. U/L Universal /local address 0 - Universally istered. 1- Locally istered. Source address (LS Bit first and MS bit Last in each byte - BigEndian style) I/G bit is always 0. U/L Universal/local address may be 0/1 MSB

LSB MSB

LSB MSB

LSB MSB

LSB MSB

LSB MSB

LSB

I/G U/L Most Significant Byte

Least Significant Byte

Organisationally Unique Identifier (OUI)

Vendor Assingned No. (Serial No.)

(3 bytes)

(3 bytes)

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

148

FDDI-Self Healing Ring

Secondary Ring

Primary Ring

Fault

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

149

Fiber Distributed Data Interface Fiber Distributed Data Interface (FDDI) is a set of standards originally designed in the late 1980s, but has since made its way into backbone networks. FDDI is a token-ing ring network that operates at 100 Mbps over twocounter-rotating fiber optic cable rings.

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

150

Topology The FDDI standard assumes a maximum of 1000 stations and a 200-kilometers (120 miles) path that requires a repeater every 2kilometers. The second ring is for backup. Single attachment stations (SAS) and dualattachment stations (DAS) are both computer that can connect to one or both of the rings, respectively. If the cable in the FDDI ring is broken, the ring can still operate in a limited fashion.

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

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Topology

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

152

Topology

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

153

Media Access Control The FDDI-MAC scheme uses a variation of the IEEE 802.5 token-ing standard. Messages and the token are sent in different frames separately in a FDDI LAN. A computer can send data only when it captures the token. When a computer on an FDDI network waiting for transmission receives the token, it holds the token and then transmits all messages that were attached to it. The computer then transmits whatever messages its wants before transmitting the token. When receiver receives the data frame it simply copy the data frame leaving it to be absorbed by the sender.

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

154

Fiber Distributed Data Interface FDDI (standardized as ANSI X3T9.5) backbone protocol was developed in the 1980s and popular during the 80s and 90s. FDDI operates at 100 Mbps over a fiber optic cable. Copper Distributed Data Interface (CDDI) is a related protocol using cat 5 twisted wire pairs. FDDI’s future looks limited, as it is now losing market share to Gigabit Ethernet and ATM. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

155

FDDI Topology (Figure 7-15) FDDI uses both a physical and logical ring topology capable of attaching a maximum of 1000 stations over a maximum path of 200 km. A repeater is need every 2 km. FDDI uses dual counter-rotating rings (called the primary and secondary). Data normally travels on the primary ring. Stations can be attached to the primary ring as single attachment stations (SAS) or both rings as dual attachment stations (DAS). ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

156

Figure 7-15 FDDI Topology

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

157

FDDI’s Self Healing Rings One important feature of FDDI is its ability to handle a break in the ring to form a temporary ring out of the pieces of the two rings. Figure 7-16, show an example of a cable break between two dualattachment stations. After the cable break is detected, a single ring is formed out of the primary and secondary rings until the cable break can be repaired. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

158

Figure 7-16 FDDI’s Self-healing Rings

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

159

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

160

Gigabit Ethernet Still under development Retains CSMA/CD protocol and Ethernet format, ensuring smooth upgrade path Uses optical fiber over short distances 1-Gbps switching hub provides backbone connectivity May not be good for LAN (explain why) and has been used in backbone networks for point-to-point connections. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

161

Gigabit Ethernet 1000BASE-LX: Long-wavelength, s up to 550m (m-mode fiber) or 5km (single-mode fiber) 1000BASE-SX: Short-wavelength, s up to 275 - 550 m(m-mode fiber) 1000BASE-CX: uses copper jumpers in a single room or equipment rack 1000BASE-T: uses 4 pairs of Cat-5 UTP ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

162

Gigabit Ethernet Media Options

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

163

Fast Ethernet Backbone

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

164

Fibre Channel combine the best features of channel and protocol-based technologies the simplicity and speed of channel communications the flexibility and inter-connectivity that characterize protocol-based network communications.

more like a traditional circuit-switched or packet-switched network, in contrast to the typical shared-medium LAN ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

165

Fiber Channel Network

N_port

F_port

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

166

Fibre Channel Elements Nodes The end systems Includes one or more N_ ports for interconnection

Fabric Collection of switching elements between systems Each element includes multiple F_ ports Responsible for buffering and for routing frames between source and destination nodes ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

167

Fibre Channel Goals Full-duplex links with two fibers per link Performance from 100 Mbps to 800 Mbps on a single link (200 Mbps to1600 Mbps per link) for distances up to 10 km Small connectors High-capacity utilization with distance insensitivity

Greater connectivity than existing multidrop channels Broad availability (i.e., standard components) for multiple cost/performance levels, from small systems to supercomputers Ability to carry multiple existing interface command sets for existing channel and network protocols

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

168

*Fibre Channel Protocol Architecture FC-0 Physical Media: Includes optical fiber, coaxial cable, and shielded twisted pair, based on distance requirements FC-1 Transmission Protocol: Defines the signal encoding scheme FC-2 Framing Protocol: Defines topologies, frame format, flow/error control, and grouping of frames FC-3 Common Services: Includes multicasting FC-4 Mapping: Defines the mapping of various channel and network protocols to Fibre Channel ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

169

Fibre Channel - Maximum Distance

800Mbps

400Mbps

200Mbps

100Mbps

10,000m

10,000m

10,000m

10,000m

M-mode

500m

1,000m

2,000m

Coaxial Cable

50m

71m

100m

100m

STP

28m

46m

57m

80m

Single Mode

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

--

170

Present IEEE 802 Project Working Groups 802.1 Higher Layer LAN Protocols Working Group 802.2 Logical Link Control Working Group 802.3 Ethernet Working Group 802.4 Token Bus Working Group 802.5 Token Ring Working Group 802.6 Metropolitan Area Network Working Group 802.7 Broadband TAG 802.8 Fiber Optic TAG 802.9 Isochronous LAN Working Group 802.10 Security Working Group

• 802.11 Wireless LAN Working Group • 802.12 Demand Priority Working Group • 802.14 Cable Modem Working Group • 802.15 Wireless Personal Area Network (WPAN) Working Group • 802.16 Broadband Wireless Access Working Group • 802.17 Resilient Packet Ring Working Group

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

171

Virtual LAN (VLAN) Virtual Local Area Networks (VLANs) are a collection of nodes that are grouped together in a single broadcast domain that is based on something other than physical location. A broadcast domain is a network (or portion of a network) that will receive a broadcast packet from any node located within that network. In a typical network, everything on the same side of the router is all part of the same broadcast domain. A switch, with the implemented VLANs on, has multiple broadcast domains, similar to a router. ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004 172

Virtual LAN (VLAN) VLANs can be created simply by logging into the switch via TELNET and then entering the parameters for the VLAN (name, domain and port assignments). Once the VLAN is created, any network segments connected to the assigned ports will become part of that VLAN. While you can have more than one VLAN on a switch, they cannot communicate directly with one another on that switch. Communication between VLANs requires the use of a router. VLANs canKSK/ span multiple ALTTC/ DX Faculty/ LAN Technology/ Nov 2004switches, and you 173

VLAN Trunking Protocol VLAN trunking protocol (VTP) is the protocol that switches use to communicate among themselves about VLAN configuration

ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004

174

VLAN Trunking Protocol In the example: Each switch has two VLANs. On the first switch, VLAN A and VLAN B are sent through a single port (trunked) to the router and through another port to the second switch. VLAN C and VLAN D are trunked from the second switch to the first switch, and through the first switch to the router. This trunk can carry traffic from all four VLANs. The trunk link from the first switch to the router can also carry all four VLANs. In that case, this one connection to the router allows the router to appear on all four VLANs ALTTC/ DX Faculty/ KSK/ LAN Technology/ Nov 2004 175 The VLANs can communicate with each other