Transcript Slide 1

AT-8948
Switch for Service Providers
Architecture and Switching
Introduction
This presentation covers the following topics:
•
Switch architecture
•
Power supplies
•
Front-to-back cooling
•
Switching tables and traffic flow
•
Switching features
•
CompactFlash
Switch Architecture
Front to back cooling
Console port
RJ45
Compact Flash
slot
1RU
4 x GbE SFP ports
48 x 10/100Base-T RJ45
Switch Architecture
PHYs
PAC interface
Switch Chip
CPU – 400Mhz
Marvel Prestera EX115
(37.6Gbps 13Mpps)
DRAM – 128MB
(up to 256 or
512MB)
IPv6 Accelerator
Interface (10Gbps)
32MB Packet
Buffer Memory
32MB Flash
Dual Hot Swappable PSUs
AC OR DC
AC OR DC
Hot-Swappable PSU
Load Sharing
PSU 1
Switch Architecture
Hot-Swappable PSU
Load Sharing
PSU 2
SDRAM (DIMM CONNECTOR)
32 MByte
Fixed
FLASH
400MHz
CPU
Compact
Flash
Battery
Backed
SRAM
INTERFACE FOR IPv6 ACCELERATOR CARD
Enviromental
Monitoring
PAC Card
Connector
Marvell
Packet Processor
Packet
Buffer
Route Lookup
Memory
Gigabit
PHY
PORT52
(SFP)
PORT51
(SFP)
PORT50
(SFP)
PORT49
(SFP)
10/100
PHY
10/100
PHY
Ports 1-16
10/100
PHY
10/100
PHY
Ports17-33
10/100
PHY
10/100
PHY
Ports 33-48
Power Supply Units - Overview
Power supply design characteristics include:
 A choice of AC or DC input PSUs
 Redundancy, load sharing, and hot swappability
 Performance monitoring
Devices – what can be
mounted in the PSU bays?
There are three devices that may be fitted into the PSU bays:
 AC power supply
 DC power supply
 Fan only module (FOM)
It’s important that both PSU bays are occupied to assist with internal cooling. If
only one PSU is fitted, a FOM must be fitted in the other bay.
FOM
AC Power Supply Features
100-240v AC auto-ranging input voltage
 High efficiency (>80%)
 Class A EMC
 Power factor correction
 Current overload protection
 Protection from current spikes
 Over temperature alarm & shutdown
 Command-line access for testing PSU operation

DC Power Supply Features
48v DC input – compatible with -48v power distributiuon bus design
 High efficiency (>80%)
 Class A EMC
 Current overload protection
 Inrush current limiting
 Protection from current spikes
 Over temperature alarm & shutdown
 Command-line access for testing PSU operation

FOM – Fan Only Module

The FOM has two cooling fans and is powered via a
back-feed from the PSU fitted in the other bay
Power Supply Redundancy,
Load Sharing and HotOne PSU is adequate to supply the switch’sSwappability
power.

If two are fitted they:
– will load share
– can be hot-swapped

If a PSU’s ‘power good’ LED is lit, it is supplying
current to the unit
What is the command to check
load-sharing performance?
Release 2.6.2 includes the command:



ACTIVATE SYSTEM PSU=[BAY1|BAY2|ALL] TEST=[LOADSHARE]
This allows the switch to check if each PSU can supply
the full load
Ensures that the remaining PSU will cope with the
extra demand when the other PSU is removed
Can you remove and replace
PSUs while the switch is
operating?
Yes, PSUs are hot-swappable

To meet regulatory requirements, two warnings are
printed on the PSUs:
– Caution: Disconnect power cord prior to removal of PSU
– Caution: Disconnect all power cords to disable system power
Command-Line PSU
Information

Some information is available via the command line
interface:


SHOW SYSTEM
This command displays the module type, revision and
serial number of each PSU or FOM that is installed,
and the current condition of the modules
Example output from
SHOW SYSTEM
command with PSU
information highlighted
Front-to-Back Cooling

The AT-8948 uses a linear
airflow arrangement, which is
designed to reduce the
amount of warm air being recirculated

Air is drawn in from the front
and expelled from the rear,
due to the action of the PSU
and FOM fans
The Benefits of Front-to-Back
Cooling



No need for ventilation clearances above, below, left
or right of the switch
Cabling clearances at front and rear of the switch are
adequate for ventilation
Ambient operating temperature range is 0 to 50C
Switching Tables



The switch makes its forwarding decisions based on the
entries in its switching tables
There are 18 hardware and 8 software tables
Some statistics:
–
–
–
–
4K IP interfaces
4K entries in the Multicast table
16K entries in the MAC table
256K entries in the IP route table
Trunking

Trunking allows a number of ports to be configured to
join together to make a single logical connection of
higher bandwidth

While the trunk group is logically a single connection,
physically it involves up to four separate links
Trunking

Hashing of information in the L2, 3,and 4 packet
headers divides traffic between the ports in the trunk
group
SCR
MAC
DES
MAC
SCR DES
IP
IP
SRC DES
Port Port
PAY LOAD DATA
When configuring trunking be
aware that:

A maximum of 7 groups may be created

A trunk group may include a maximum of 4 ports

Ports in a trunk group need not be contiguous

Ports in a trunk group must belong to the same VLAN
and have the same tagging status
When configuring trunking be
aware that (continued)

All ports in a trunk group must be added to VLANs
together, and can only be removed from a VLAN as a
group

If the tagging status of the ports in a trunk group is
changed, it must be changed for all ports in the trunk
group at the same time
When configuring trunking be
aware that (continued)

Ports in a trunk group are set to autonegotiate at the
trunk speed at full duplex

When a port is added to a trunk group, the speed
setting for the group overrides the speed setting
previously configured for the port
When configuring trunking be
aware that (continued)

When a port is removed from a trunk group, the port
returns to its previously configured speed and duplex
mode settings

A trunk group may not include both 10/100 Ethernet
ports and Gigabit Ethernet ports
When configuring trunking be
aware that (continued)

A trunk group may not include a mirror port

The port trunking algorithm used on the AT-8948 may
be compatible with that used on third-party devices
VLAN Double Tagging Available in
2.6.2



An enterprise with multiple VLANs across multiple sites
in a metropolitan area can use a public MAN to carry
VLAN-tagged traffic between its sites
The public MAN carries traffic for multiple customers,
so each frame must carry ‘customer-ID’ information
A second VLAN tag is inserted into each frame as it
enters the public network and is removed on egress
VLAN Double Tagging
Customer A
Site 2
VLANs 1,2,3
Customer A
Site 1
VLANs 1,2,3
AT-8948
AT-8948
Metro
Ethernet network
Customer B
Site 1
VLANs 1,2,3
AT-8948
Customer A
Site 3
VLANs 1,2,3
Customer B
Site 2
VLANs 1,2,3
Customer B
Site 3
VLANs 1,2,3
SwiA_DoubleTag
VLAN Double Tagging

‘Familiar’ VLAN tagging: a 4-byte field is inserted into
Ethernet frames
Max Frame size
is 1518 bytes
6
6
2
46 to 1500
4
DA
SA
LEN / EType
Payload Data
FCS
Original
Ethernet
Frame
Max Frame size
becomes 1522
bytes
6
6
4
2
46 to 1500
DA
SA
TAG
LEN / EType
Payload Data
4
FCS
VLAN-tagged
Ethernet Frame
SwiA_Frame1
VLAN Double Tagging

When a frame enters the public MAN, a second, ‘percustomer’ VLAN tag is inserted
Max Frame size
becomes 1526
bytes
6
6
DA
SA
4
TAG
4
TAG
2
46 to 1500
4
LEN / EType
Payload Data
FCS
Double tagged
Frame within
provider network
SwiA-Frame2
Configuring VLAN doubletagging
Create the nested VLAN, specifying the customer-ID

CREATE VLAN={vlan-name VID=2..4094} NESTED
Configuring VLAN doubletagging
Two types of ports are defined:
 Customer ports connected to customers’ LANs:


ADD VLAN={vlan-name|2..4094} PORT=port-list
NESTEDTYPE=CUSTOMER
Core ports connected to the public MAN

ADD VLAN={vlan-name|2..4094} PORT=port-list NESTEDTYPE=CORE
Configuring VLAN doubletagging
To operate with other vendors’ equipment, it may be
necessary to change the ‘Ethertype’ value in the
customer-ID tag from its default value of 0x8100:

SET SWI NESTEDTPID=TagNumber
VLAN Double Tagging

Customer-ID tag
6
6
4
4
2
46 to 1500
4
DA
SA
TAG
TAG
LEN / EType
Payload Data
FCS
2 bytes
2 bytes
EType
TAG Control
IDENTIFIER
8
7
User Priority
6
5
CFI
4
3
2
1
8
7
6
5
4
3
2
1
12bit VID (VLAN ID)
Archswi_NTA3
Private VLANs Available in 2.6.2
A Private VLAN is a VLAN which contains a specified
group of ports that are prevented from communicating
with each other at Layer 2.
(Also known as a protected or port-protected VLAN)
Private VLANs

A typical application is in hotel installations where each
room is serviced by one 10/100 Ethernet port, through
which the hotel guest is able to access the Internet. In
this situation it is undesirable to allow communication
between rooms.
INTERNET
One customer is not able
to snoop on the traffic
from any other, yet each
customer is able to
access another network
(usually the Internet).
Private VLANs
AT-8948
AT-8948
X
10.1.1.99/24
Private VLAN 101
10.1.1.100/24
SwiA_PVlan1
Private VLANs

Ports that are members of a Private VLAN have one of two states, either 'private'
(protected) or 'uplink'

Private ports cannot talk to other private ports but can talk to uplink ports. Uplink
ports can talk to both private and other uplink ports, if they exist
Private VLANs

All traffic received on any private port in a Private VLAN is sent to the predefined
uplink port, and only that uplink port, regardless of VLAN ID or MAC Destination
address

Layer 2 traffic between private ports that are members of a Private VLAN is blocked
Configuring Private VLANs

Create a private VLAN using the command:


Add the private ports to the VLAN:


CREATE VLAN=vlan-name VID=2..4094 PRIVATE
ADD VLAN={vlan-name VID=2..4094} PORT=port-list
Add the uplink port(s) to the VLAN:
ADD VLAN={vlan-name VID=2..4094} PORT=port-list UPLINK
If the uplink ‘port’ is a trunk group, the trunk group must be created before the ports are added to the
private VLAN

CompactFlash
CompactFlash
CompactFlash is:



A small removable mass storage device that uses FLASH memory
Memory that doesn’t require power from a battery to retain stored data
Used to expand the amount of FLASH memory available to store files on the switch
CompactFlash
Two CompactFlash cards have been approved for the AT-8948:
AT-CF032A-n 32MB CompactFlash card
AT-CF0128A-n 128MB CompactFlash card
Where n is the number of cards in a package
(The size of the release file 89-261.rez is in the order of 6MB)
QoS
Feature
– Eight priority/egress queues per port
Benefits
–
–
–
–
Allows traffic to be processed with up to eight levels of priority
Gives greater control to the network administrator
Increases differentiation of critical and non-critical network applications
Ensures availability of business-critical applications and services
 Catalyst 3550/3750 Metro
–
4 egress queues per port
QoS
Features
–
–
Bandwidth limiting down to 3Kbps, with burst limits
Bandwidth limit resolution down to 1Kbps
Benefits
–
–
Very precise control of bandwidth guarantees
Burst limits improve bandwidth limiting of TCP sessions (avoids bandwidth flapping)
 Catalyst 3750 Metro
–
rate limiting at 8 Kbps increments
“The bandwidth limiting
capabilities of the 8948 are
frightening!” – Senior Test
Engineer, 8948 Development
Team, ATR.
QoS
Feature
– 2 rates & 3 colours of bandwidth conformance
Benefits
– Allows SPs to offer differentiated services based on SLA
– Customers exceeding their guaranteed SLA bandwidth can be given lower
priority using re-marking
– Non-conforming traffic can be identified through the entire network
 Catalyst 3750 Metro
–
2 rate 3 colour (CIR/EIR) rate limiting
QoS – Rate Metering
Traffic Class
Bandwidth
Immediate Discard
on Ingress
Bandwidth
Class 3
MAXBURSTSIZE
MAXBANDWIDTH
RED Discard
Excess Burst Size (EBS)
Re-mark
Excess Information Rate (EIR)
Bandwidth
Class 2
MINBURSTSIZE
MINBANDWIDTH
Re-mark
Committed Burst Size (CBS)
Committed Information Rate (CIR)
Re-mark
Bandwidth
Class 1
Re-marking options :
bandwidth class
DSCP
Egress Queue
Time
VLAN Tag User Priority
QoS – Common CoS-based
SLA
Service
Class
Premium
Silver
Bronze
Standard
Service
Characteristics
802.1p
ID
Bandwidth
Profile
Service
Performanc
e
6, 7
CIR
No EIR
Delay < 5ms
Jitter < 1ms
Loss < 0.01%
Bursty mission critical data
applications requiring low loss
and delay (e.g., Storage)
4, 5
CIR
EIR
Delay < 5ms
Jitter = N/S
Loss < 0.01%
Bursty data applications
requiring bandwidth
assurances
3, 4
CIR
EIR
Delay < 15ms
Jitter = N/S
Loss < 0.1%
No CIR
Delay < 30ms
Jitter = N/S
Loss < 0.5%
Real-time IP telephony or IP
video applications
Best effort service
0, 1, 2
IPv6 – Why?
Increased
address space
– IPv4: 32 bit address gives 4 billion addresses
– IPv6: 128 bit address gives 340 billion billion billion billion
addresses!!!!
end-to-end networking – Removes need
for NAT
True
– Some countries in Asia, with only a small IPv4 address allocation,
have NAT up to 6 layers deep!
– Some countries are running out of addresses now!
Increased
security
Better QoS – Flow labels
Automatic configuration
IPv6
Feature
– Dual IPv4 and IPv6 stack
Benefits
– IPv6 routing in software as part of feature set – DHCPv6, RIPng, multicasting
– Ideal for early adopters looking for IPv6 compatibility now


Universities
Government/Military
– Allows IPv4 and IPv6 to coexist in the same networks, easing transition to
IPv6
IPv6
Feature
– IPv6 accelerator card ACC-01
Benefits
–
–
–
–
–
–
Ideal for customers who demand IPv6 compatibility and
high performance IPv6 routing
Provides wire speed hardware routing for IPv6 packets
Provides wire speed QoS – prioritisation and rate
limiting
Accelerates tunnelling
Can sell as upgrade option for AT-8948A customers
wanting future IPv6 capability
Future proofed


Start with IPv4 box
Sell IPv6 upgrade later
IPv6
Feature
– Tunnelling
Benefits
– Future-proofs your network
– Allows early adopters to implement IPv6 at the edge, retaining IPv4 core
– IPv4 and IPv6 will co-exist for some time. Tunnelling eases transition to IPv6.
IPv6 Tunnelling Application
IPv4 Internet
AT-8948
AT-8948
IPv6
IPv6
IPv4
IPv4
End of presentation