LAN IP TECHNOLOGIES

1 © Nokia Siemens Networks

LAN Technologies

Router

2 © Nokia Siemens Networks TG70112EN02GLA1

802.3 802.5 802.11 ISO9314

CSMA/CDMAC

Token RingMAC

WLANMAC

FDDIMAC

Logical Link Control (LLC)802.2

Phy

Dat

a Li

nkProtocols of the network layer

802.4

Token BusMAC

IEEE Layer 2 protocols

MAC … Media Access Control


SIEMENSNIXDORF SIEMENSNIXDORF SIEMENSNIXDORF SIEMENSNIXDORF

Ethernet FrameHeader contains MAC Addresses

Ethernet FrameHeader contains MAC Addresses

DA=4

1 432

Oh!My address.

I‘ll read the packet

Oh!My address.

I‘ll read the packet

Nothing to do with me.Not my

MAC address

Nothing to do with me.Not my

MAC address

Data transmission within an Ethernet LAN


Ethernet Frame (native frame)

General overhead:The Ethernet frame consists of a preamble with 8 bytes, the minimum frame size of 64 bytes and an interframe gap with 12 bytes. The following diagram is an example:

Preamble SDDestination

AddressSource Address

Type DataFrameCheck

Sequence

7 Bytes 1 Byte 6 Bytes 6 Bytes 2 Bytesvariable length46 to 1500 Bytes

64 Byte ≤ frame size ≤ 1518 Byte

4 bytes

Ethernet - FrameEthernet - Frame

InterframeGap

12 bytes

Result:84 byte for a minimal frame – 1538 byte for maximal frame length Preamble, Start delimiter (SD) and interframe gap are negligible for long packets, but a significant contribution in case of short packet length (e.g. around 100 bytes for VoIP)


Ethernet Frames and MAC Addressing

Destination MAC

SourceMAC

TypeField

Checksum

Data of Layers 3 to 7

6 Bytes 6 Bytes 2 By 4 Bytes

The Type Field: specifies, which Layer 3 Protocol is contained

The Checksum (CRC) secures both addresses, type field and data

up to 1500 Bytes

Ethernet Frame

MAC-Address : (Media Access Control)Address on Layer 2 most commonly used on Ethernet, 6 Bytes long,linked to Hardware, worldwide unique

MAC-Broadcast addresses all stations on a LAN (Address = ff:ff:ff:ff:ff:ff)

MAC-Multicast addresses all stations with a particular propertye.g. all switches supporting a particular protocol

Data Link

Network

Transport

Session

Presentation

Application

Physical


Ethernet Switching 1/2

11 22 33 44

SAT – Table or MAC-Address-Table

(SAT = Source-Address-Table)

Port Address

1

2

3

4

08:00:06:00:00:0A 08:00:06:00:00:0B 08:00:06:00:00:0C 08:00:06:00:00:0D

Src: 08:00:06:00:00:0ADst: 08:00:06:00:00:0C

Src: 08:00:06:00:00:0ADst: 08:00:06:00:00:0CSrc: 08:00:06:00:00:0CDst: 08:00:06:00:00:0A

Src: 08:00:06:00:00:0CDst: 08:00:06:00:00:0A



Port Address

1 08:00:06:00:00:0A

2

3

4



Port Address

1 08:00:06:00:00:0A

2

3 08:00:06:00:00:0C

4



Port Address

1 08:00:06:00:00:0A

2 08:00:06:00:00:0B

3 08:00:06:00:00:0C

4 08:00:06:00:00:0D

????<unknown><unknown><unknown><unknown>

flooding


Ethernet Switching 2/2

• The Forwarding Table is learnt dynamically from the packet’s source addresses

• If the destination MAC address is not known, the packet is “flooded”, which means it is forwarded to all ports

• If the destination MAC address is known, the packet is only forwarded to the port where the address has been learnt

• Broadcast (eg ARP) and Multicast (without IGMP Snooping) messages are always flooded


IEEE 802.3 Frame Capture


The LLC (Logical Link Control) sublayer

Media Access Control

hardware dependent

Logical Link Control

hardware independent

NetworkNetworkNetwork

Data LinkData LinkData Link

PhysicalPhysical

LLCLLCLLC

MAC FrameMAC Frame 802.2 LLC802.2 LLC802.2 LLC Layer 3 dataLayer 3 data

MACMAC


DSAP SSAP Control Field Data

1 Byte 1 Byte 1Byte variabel

LPDU (IEEE 802.2)

This is the address of a network layer protocol

This partcontains information

The most important SAPs: BPDU 42 Bridge Protocol Data Unit (Spanning Tree) Banyan BC Banyan Vines IBMNM F4 IBM Network Management IP 06 Internet Protocol ISO FE International Standard Organization NetBIOS F0 Network Basic I/O System Novell E0 Novell (NetWare) RPL F8 Remote Program Load SNA 04, 05 , 08, 0C Systems Network Architecture SNAP AA Sub Network Access Protocol Global FF Broadcast Null 00 IBM SAP Negotiation They are inserted into the DSAP/SSAP Octet

LPDU (LLC Protocol Data Unit)


PreambleFrameDeli-meter

DestinationAddress

SourceAddress

Length Data Checksum

DataControlField

SSAPDSAP

Now, the service access point (SAP) defines...

... which protocol isincluded here

Protocol-ID/Organization = 0

Control FieldLLC-Type 1

SSAP0x AA

DSAP0x AA

Ether-Type(e.g. ARP 0x 806)

Data

Now, the SAP defines...

... that a SNAP header follows...

... and the header defines which protocol follows

and with SNAP:

standard encapsulation:

Ethernet Frame (IEEE 802.3, 802.2) with LLC


L2-Switch

The switch and I can talk 100 Mbitsper second!

1 Gbps one way and 1 Gbps the other way, that sums up to 2 Gbps….

But I‘m on full duplex. The switch and I can use the full 1Gbps link capacity at the same time.

L2-Switch

Yes, that‘s called ‚California Count‘. It‘s a popular way to express switching capacities. Instead of saying you can switch 320 Gbps Full Duplex you could say you have 640 Gbps switching capacity.

Full-duplex operation is restricted to point to poi nt linksconnecting exactly two stations.

But if we talk at the same time, we‘re in trouble*. You‘re on a half duplex link.

*requires CSMA/CD

Half Duplex – Full Duplex


Ethernet Auto -Negotiation

• Twisted-pair Auto-negotiation defines a standard to address the following:– Provide easy, plug-and-play upgrades from 10 Mbps, 100 Mbps, and 1000

Mbps as the network infrastructure is upgraded– Prevent network disruptions when connecting mixed technologies such as

10BaseT, 100BaseTX and 1000BaseT– Accommodate future PHY (transceiver) solutions– Allow manual override of auto-negotiation– Support backward compatibility with 10BaseT– Provide a parallel detection function to recognize 10BaseT and 100BaseTX

non-auto-negotiation devices– Mandatory auto-negotiation for 1000BaseT– Configure master and slave modes for the PHY

• Fiber optic Auto-negotiation– Only defined for the 1000BASE-X fiber optic media system– Used by the link partners on a Gigabit Ethernet fiber optic link to determine

which modes of operation they support in common (e.g., full-duplex, PAUSE operation)


Virtual LAN (VLAN)Broadcast Domain Separation

VLAN1 -> Broadcast Domain



L2-Switch L2-Switch

Several logical networks (VLAN) share one physical media (LAN)

VLANs are used for customer separation


10.0.0.254/24 10.0.1.254/24

IP 10.0.0.1/24GW 10.0.0.254

IP 10.0.1.1/24GW 10.0.1.254

IP 10.0.0.2/24GW 10.0.0.254

IP 10.0.1.2/24GW 10.0.1.254

Virtual LAN 1/2

11 22 33 44

08:00:06:00:00:01 08:00:06:00:00:02 08:00:06:00:00:03 08:00:06:00:00:04

SAT – Table (MAC-Address-Table)

Port Address VLAN-ID

1 08:00:06:00:00:0A 1

2 08:00:06:00:00:0B 2

3 08:00:06:00:00:0C 1

4 08:00:06:00:00:0D 2

SAT – Table (MAC-Address-Table)

Port Address VLAN-ID

1 08:00:06:00:00:0A 1

2 08:00:06:00:00:0B 2

3 08:00:06:00:00:0C 1

4 08:00:06:00:00:0D 2

5 08:00:06:00:00:10 1,2

55

08:00:06:00:00:10


Virtual LAN 2/2

• Switch ports are logically grouped with the help of VLANs (PVID)

• Each group behaves like an individual switch

• Inter-VLAN communication is only possible with a router


Ethernet FrameVLAN

Additional Bytes:In a VLAN-tagged frame 4 bytes are added between the Type-Field and the Data-Field

Preamble SDDest.

AddressSourceAddress

DataFrameCheck

Sequence

7 Bytes 1 B. 6 Byte. 6 Byte 2 B.46 to 1500 Bytes 4 bytes

Ethernet II – Frame (with VLAN tag)Ethernet II – Frame (with VLAN tag)

InterframeGap

12 bytes

TypeTCI

TPID (Ether type)Tag protocoll identifier

TCITag Control Information

3 1 12Defines type of 802.1q tag

2 B. 2 B.

User priority CFI (Cannonicalformat identifier)

VLAN ID(n <= 4094)

Total Ethernet Frame Size68...1522 Byte(without Preamble, SD and Interframe Gap)

TPIDTPID TCI


Is forwarded to any port (except the receiving port)

The problem is solved by STP = Spanning Tree Protocol

Ethernet Protection Mechanisms 1/2

An incoming Ethernet packet with unknown destination…

So it‘s obvious that Loops lead to problems (a.k.a. “Broadcast storm”).

Here it‘s also „nice“ thatEthernet packets have no time to live counter


Ethernet Protection Mechanisms 2/2

STP blocks the network at certain links

So loops are avoided

This can also be used for protection – if another link goes down, the block is released

STP Variants:- STP (tens of seconds protection switching time)- RSTP (Rapid STP, around one second): the protection links are pre-calculated by the switches: Faster, but manual configuration of switches required, some configurations required (root bridge, backup root bridge)- PV(R)STP: RSTP per VLAN- MSTP: RSTP per VLAN-Groups, scales much better than RSTP / PV(R)STP


Other Spanning Tree Operational Modes

• Spanning Tree – 802.1D• Rapid Spanning Tree – 802.1w

- Faster than 802.1D due to better Topology Change m echanisms (reconfiguration within 1s)

• Per VLAN Spanning Tree (PVSTP)- Uses same mechanism as 802.1D but independent for each VLAN- Scalability problem (~ 128 VLANs at a time)

• Per VLAN Rapide Spanning Tree (PVRSTP)- Uses same mechanism as 802.1w but independent for each VLAN- Scalability problem (~ 128 VLANs at a time)

• Multiple Spanning Tree – 802.1s- Same recovery time as 802.1w- Allows grouping of VLANs into regions instances wit hin a region - Only one BPDU per region is necessary


Tagged Port

in order to reduce the number of Switch-to-Switch and Switch-to -Router connections additional information (tags) for the VLAN association is inserted into the Ethernet frame.

A “tagged” port is part of several VLANs and Broadcast Domains.

12

12

ports are assigned simultaneous

frame with tag1

2

LAN IP TECHNOLOGIES

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