evolving enterprise network architecture
TRANSCRIPT
2
Some of the forces driving WLAN (re)design
Migration to IPv6Consumer devices
in the enterprise
Migration to the
cloud
3
Why do we need VLANs?
• VLANs split up L2 subnets to control excessive broadcast & multicast traffic
• We sometimes use VLANs to segregate traffic for security
• VLANs can help us manage geographically distributed networks (addresses imply location)
• We sometimes use VLANs to segregate services and QoS
• We‟ve always done it this way
• VLAN pooling has been a widely-used (and useful) feature…
4
Why do we need VLANs?
• VLANs split up L2 subnets to control excessive broadcast & multicast traffic
• We sometimes use VLANs to segregate traffic for security
• VLANs can help us manage geographically distributed networks (addresses imply location)
• We sometimes use VLANs to segregate services and QoS
• We‟ve always done it this way
• VLAN pooling has been a widely-used (and useful) feature…
But…
• VLAN pooling causes inefficient address usage
• And IPv6 (SLAAC) VLANs don‟t mix well with WLANs
• And managing multiple VLANs across a large network is challenging
5
Moving WLANs to IPv6 – SLAAC
VLAN 1
1. RS to ff02::2 ICMPv6 type 133 (RS)
2. RA to ff02::1 ICMPv6 type 134 (RA)
router lifetime 1800s
preferred lifetime = 7d,
valid lifetime = 30d
RS
RS
RA RS
RA
RS Router Solicitation
RA Router Advertisement
SLAAC Stateless Address Auto-Configuration
DAD Duplicate Address Detection
ND, NS, NA Neighbor Discovery, Solicitation, Advertisement
MACAddress
Network Identifier
64 bits
Interface Identifier
64 bits
2001:0db8:1010:61ab:0219:71ff:fe64:3f00
• IPv6 address discovery with SLAAC
(State-Less Address Auto
Configuration, RFC 4862)
• Routers send unsolicited Router
Advertisements (RA) periodically (~
minutes)
• RA includes the „network‟ stub for the
address, device adds a unique interface
identifier to construct an address in a
stateless protocol
• But more often, a device requests an
address by sending a Router Solicitation
(RS) to the well-known „all routers‟
address
• Controller assigns device to a pooled
VLAN and forwards the RS to only the
appropriate router
• On receipt of an RS, the router sends an
RA to the all-nodes multicast address
6
Moving WLANs to IPv6 – RAs meet wireless
VLAN 1
1. RS to ff02::2 ICMPv6 type 133 (RS)
2. RA to ff02::1 ICMPv6 type 134 (RA)
router lifetime 1800s
preferred lifetime = 7d,
valid lifetime = 30d
RA
RA
MACMACAddress list Address list
RAs multicasts are limited within their VLAN by
switches…But 802.11 has no concept of VLANs or
multicast, only broadcast to all associated devices.
So an RA for a device on one VLAN is received by
devices on other VLANs. This affects BSSs serving
devices from more than one VLAN, which comes about
after mobility events or through VLAN pooling.
• IPv6 address discovery with
SLAAC (State-Less Address Auto
Configuration, RFC 4862)
• Controller assigns device to a pooled
VLAN and forwards the RS to only the
appropriate router
• On receipt of an RS, the router sends
an RA to the all-nodes multicast
address
• Controller forwards the multicast RS to
all APs with a member of that
multicast group
• RAs are broadcast over the air, all
associated devices receive them
7
Consumer devices in the enterprise
• Several scenarios result in clients
from multiple VLANs associating to
the same AP
• This sows the seeds of the VLAN‟s
demise
• Mixed VLAN clients on one AP:
i. Through VLAN pooling, by design
ii. From mobility events, where
devices move from one AP to
another
iii. Where VLANs are used to
segregate, or manage traffic and
clients are using different services
8
Moving WLANs to IPv6 – multiple VLANs
VLAN 1 VLAN 2
2. RA to ff02::1 ICMPv6 type 134 (RA)
router lifetime 1800s,
preferred lifetime = 7d,
valid lifetime = 30d
RA
RA
RA
RA
MAC
MACMAC
MAC
MACMAC
Address list Address list
With IPv6, devices construct multiple addresses, one per distinct RA received,
by adding its MAC address to the RA global_routing_prefix + subnet_id.
A device may choose to use any address from its list as its source address.
• IPv6 address discovery with SLAAC
(State-Less Address Auto
Configuration, RFC 4862)
• Controller assigns device to a pooled
VLAN and forwards the RS to only the
appropriate router
• On receipt of an RS, the router sends an
RA to the all-nodes multicast address
• Controller forwards the multicast RS to
all APs with a member of that multicast
group
• RAs are broadcast over the air, all
associated devices receive them and
build multiple addresses
9
• IPv6 address discovery with SLAAC
(RFC 4862)
• Controller assigns device to a pooled VLAN
and forwards the RS to only the appropriate
router
• On receipt of an RS, the router sends an RA
to the all-nodes multicast address
• RAs are broadcast over the air, all devices
receive them
• Devices build multiple IPv6 addresses based
on heard & overheard RAs
• When a device starts to transmit, only one of
its IPv6 addresses matches the controller‟s
VLAN mask. Packets with mismatched
source addresses are dropped.
Moving WLANs to IPv6 – confused addressing
VLAN 1 VLAN 2
1. RS to ff02::2 ICMPv6 type 133 (RS)
2. RA to ff02::1 ICMPv6 type 134 (RA)
router lifetime 1800s,
preferred lifetime = 7d,
valid lifetime = 30d
RA
RA
RA
RA
MAC
MACMAC
MAC
MACMAC
Address list Address list
The network learns VLAN assignments and check for incorrect source
address as a security measure (e.g. anti-spoofing).
10
• IPv6 SLAAC with VLAN
pooling
• Where APs serve clients with
mixed VLANs, some percentage
of devices use the wrong address
and traffic is dropped
• Solution: turn downstream
multicast to unicast
• But devices still hear all RAs on
the VLAN, regardless of where the
RS came from. This can be a
significant amount of extra traffic
Moving to IPv6 – Solving mismatched IPv6
VLAN 1 VLAN 2 VLAN 3
VLAN 1 VLAN 2
RA
RA
RA
RA
MACMAC
Address list Address list
11
• Multicast-to-unicast of IPv6 SLAAC
RAs results in noticeably faster battery
drain
• This appears to be a combination of the
client radio staying in receive mode for
longer periods (stays awake till it can
contend for an uplink trigger frame)…
• And extra transmit operations to send
frames required to retrieve buffered
downlink and return to sleep mode
Moving to IPv6 – Unicast vs Multicast
beacon TIM multicast
client radio in receive mode
beacon TIM multicast
client radio in receive mode
unicast
client transmits
trigger
data ack
&
sleep
time
time
Multicast downlink frames
Multicast to unicast downlink frames
12
• IPv6 SLAAC with VLAN pooling
• Where APs serve clients with mixed
VLANs, some percentage of devices
use the wrong address and traffic is
dropped
• Solution: turn downstream multicast to
unicast
• But now devices still hear all RAs on the
VLAN, regardless of where the RS came
from. This can be a significant amount of
extra traffic … and this unicast traffic is a
significant drain on battery life
Moving to IPv6 – Solving mismatched IPv6
VLAN 1 VLAN 2 VLAN 3
VLAN 1 VLAN 2
RA
RA
RA
RA
MACMAC
Address list Address list
• What to do? Either…
i. Prune RA traffic to only those devices that have
outstanding RSs?
ii. Make sure we don‟t mix VLANs on an AP?
iii. Try making Wi-Fi VLAN-compliant?
iv. Other ideas?
13
Some of the forces driving WLAN (re)design
Consumer devices in
the enterprise
Migration to
IPv6
Migration to the
cloud
14
Consumer devices in the enterprise
• Consumer devices on a home
network
• Reference model is a small L2
network
i. Not many devices, plentiful
bandwidth
ii. Devices use multicast to discover
each other, and services by Type
and Name
iii. … through mDNS / DNS-SN /
Bonjour
15
mDNS and DNS-SD
mDNS Query- serviceType (e.g.PTR)
- domain mDNS Response- serviceName (e.g. GammaPrinter)
mDNS Response- serviceName (e.g. BetaPrinter)
mDNS Response- serviceName (e.g. AlphaPrinter)
RFC 6762 Multicast DNS
RFC 6763 DNS-based
service discovery
DNS Domain Name Service
L2 network
When a new service instance starts, it advertises the service to a multicast address with serviceType and serviceName.
Listening devices add the service to their cached list.
When an app requests a service by serviceType queries the OS-cached list for optional mDNS Query for the serviceType.
When an app wants to use a service, mDNS Queries resolve the chosen serviceName to a hostName and IP address + port
Some DNS-SD Service Types
http://www.dns-sd.org/ServiceTypes.html
http http
ipp printer
appletv Apple TV
home-sharing iTunes Home Sharing
ServiceType : NameServiceType : NameServiceType : NameServiceType : Name
App
advertises
serviceApp
requests
service
Announcements
Queries
Responses
Announcements
mDNS Advertisement- serviceType (e.g.PTR)
- domain
16
• mDNS & DNS-SD
i. Every service instance
publishes/advertises
when it comes up and
responds to queries on
multicast.
ii. Within a given service,
all instances have
visibility of all other
instances…
iii. … except across VLAN
or L2 boundaries
iv. Default is to flood
packets
mDNS & DNS-SD
VLAN 1
VLAN 3
VLAN 2
17
• mDNS & DNS-SD with
network participation
i. „Network‟ learns groupings by
service and device
ii. When a service instance transmits
(on multicast mDNS), the network
swallows the transmission
iii. Network responds to mDNS DNS-
SD Queries on behalf of service
instances
iv. When other devices in the group
are in different VLANs, packets
are forwarded across VLAN
boundaries
v. Default may be to block mDNS
per-service
mDNS-participating network architecture
Rules to determine control forwarding
(examples)
• Allow X service on the network
• Allow device/instance Y to see service
instance X because
- They are instances of the same service
- They are on the same AP
- They are in the same building
- They „owned‟ by the same userid
- Y has been „authorized‟ by the „owner‟
of X
- They are instances of an „uncontrolled‟
service
- X has been designated a „shared‟
instance
(ethersphere) #show airgroup status
AirGroup Service Information
----------------------------
Service Status
------- ------
airplay Enabled
airprint Enabled
itunes Disabled
allowall Disabled
(ethersphere) #show airgroup blocked-queries
AirGroup dropped Query IDs
--------------------------
_touch-remote._tcp 81834
_sleep-proxy._udp 2
_vnc._tcp 1819
_mediatest._udp 91
_mediatest._tcp 22
• Network intercepts mDNS service advertisements
• Transmits advertisements to selected devices on any VLAN
• Responds to service queries by sending selected responses
VLAN 1 VLAN 2
18 @arubanetworks
Consumer devices in the enterprise
• mDNS & DNS-SD with
network participation,
network must be capable
of:
i. Identifying whether a service
type is allowed
ii. Identifying the „group‟ which
should have visibility of each
service instance
19
Subnets, VLANs and multicast control
VLANs: network controls what a port can see Subnets: L2 domains require a router to connect, breaks
multicast
Multicast control: similar to VLANs but works across subnets
20
‘Proxy’ multicast architecture is not new
• Proxy ARP has been a feature
of over-the-air WLANs for
years, to limit traffic and
provide security
• Concept extends to multicast
control
• Also extends to IPv6 duplicate
address discovery, neighbor
discovery
Who has
A.B.C.D?A.B.C.D
Over here,
mate!
ARP RFC 826
Multicast query
Unicast response
ARP proxy
(802.11v, u
e.g. ARP)
Multicast filtering
(802.11v FBMS
e.g. VRRP)
IPv6 Neighbor Discovery
Proxy
(e.g. NDP, ND, DAD)
21
Traffic forwarding layer
Policy layer
Identifies, synthesizes and forwards
specific packets
applies rules, e.g. “this device or service
instance is part of group X including these
other members”
• mDNS & DNS-SD with network
participation
i. Network takes the role of service directory away
from the distributed mDNS model
ii. Network can add and advertise its own services
mDNS-participating network architecture
mDNS Query- serviceType
- domain
mDNS Response- serviceName
- (e.g. AlphaPrinter)
mDNS
Advertisement- serviceType
- domain
mDNS
proxy
External Configuration for
groupings, permissions
Internal policy
decisions
22
Some of the forces driving WLAN (re)design
Migration to
the cloud
Consumer devices
in the enterprise
Migration to
IPv6
23
• Monitoring and managing corporate activity
from remote locations to cloud-resident
applications
i. „Conventional‟ model brings traffic to the data
center from campus APs
ii. And remote APs (VPN model over Internet)
iii. As corporate locations become more distributed, and
apps & services become cloud-resident, network
managers become blind to corporate traffic
iv. The only touch point for network managers will be
an IT-supplied and managed AP
Monitoring and control at the network edge
Functions performed at the network edge:
Radio configuration, monitoring and management…
Authentication
Firewall rules
Traffic shaping and QoS
Monitoring & reporting
Access for troubleshooting
24
Some of the forces driving WLAN (re)design
Migration to
IPv6
Consumer devices in
the enterprise
Migration to
the cloud
• New WLAN features in response to specific problems
• Multicast control (filtering & forwarding) is a powerful new technology
• An opportunity to re-think network design
25
Increase the size, reduce the
number of VLANs to solve IPv6
issues
Why do we need VLANs?
• Solved by network multicast
control
• Solved (as well as it was by
VLANs)
• Mobility-aware network does this
better
Single-VLAN networks can be an IPv6 overlay
over existing IPv4 designs…
Or an opportunity to simplify the whole network
VLAN 1VLAN 2VLAN 3
IPv4 IPv6
• VLANs split up L2 subnets to control
excessive broadcast & multicast traffic
• We sometimes use VLANs for security
• VLANs can help us manage geographically
distributed networks (addresses imply
location)
• We sometimes use VLANs to segregate
services and QoS
26
Software Defined Networking (SDN)
SDN Benefits
Centralized management and control of networking devices from multiple vendors
Increased network reliability, security, uniform policy enforcement, and fewer configuration errors
Granular network control with the ability to apply comprehensive and wide-ranging policies at the session, user, device, and application levels
Better end-user experience as applications exploit centralized network state information to seamlessly adapt network behavior to user needs.
• Software-defined networking
decouples network control (routing
and switching traffic) from the
physical network topology
• Network intelligence and state are
centralized, network topology is
abstracted and virtualized
• The Open Networking Foundation
consortium is leading
standardization efforts
• https://www.opennetworking.org/
• OpenFlow is a protocol that
facilitates communication between
SDN Controllers and SDN capable
network elements.
* https://www.opennetworking.org/images/stories/downloads/white-papers/wp-sdn-newnorm.pdf
27
Traffic forwarding layer
Policy layer
identifies, synthesizes and forwards specific
packets
applies rules, e.g. “this device or service
instance is part of group X including these
other members”
• Abstract the network
model to a policy layer
• Policy layer interfaces to
external APIs, OpenFlow
• External APIs export
sensing information,
accept reconfiguration
Abstracting the network model
Move to
another
AP
Internal policy
decisions
Voice / Video Server
Connection
setup alert
Security / Remediation Server
New device alert
Required action
(response)
New
ACL /
firewall
Adjust
QoS per
stream
Can‟t do this
one, try again
28
Sensing at the network edge
• Only at the edge can the
network sense
• Device radio characteristics
• Device authentication status
• Unassociated devices
• All intrusion attempts
Radio
information
- Signal level
- SNR
radio 802.11
mgmt
802.11
management
- Associated
- Data rate
- Frame error
rate
- MAC
- Sleeping
Authenticati
on
- Status
- Identity
- Role
- Blacklist
L2
- ARP
- VLAN
- mDNS
IP
- DHCP
- IP
address
Multicast
- IGMP
- MC
Neighbors
L4-7
- Sessions &
protocols
- Destinations,
ports
- Rates
- QoS
Mobility
awareness
- Origin &
location
- Roaming
history
- AP load
- Neighbor APs
L2 traffic
& services
L3 traffic
& services
802.11 connected device
29
Control at the network edge
• Only at the edge can the network control all aspects of association,
authentication, discovery and connectivity
• e.g. blacklist association based on traffic protocol
• e.g. move APs based on a new session
Radio information
- Signal level
- SNR
802.11 management
- Associated
- Data rate
- Frame error rate
- MAC
- Sleeping
L2
- ARP
- VLAN
- mDNS
IP
- DHCP
- IP address
Multicast
- IGMP
- MC Neighbors
L4-7
- Sessions & protocols
- Destinations, ports
- Rates
- QoS
Mobility awareness
- Origin & location
- Roaming history
- AP load
- Neighbor APs
802.11 connected (or unconnected) device
Blacklist
association
Apply or
change
QoS
Devices &
services
discovery
Determine
Reachability
Synthesize
responsesMove to
„best‟ AP
30
A better way to think about architecture
Sensing layer
Policy enforcement layer
Local policy decision layer
SDN policy decision layer
report radio state, 802.11 state,
authentication, multicast services, traffic
apply authentication rules, firewall rules,
QoS policy, multicast service manipulation
Abstract the wireless network model and make decisions
for authentication, service whitelisting, load balancing…
reconfigure network to allow for changes and coordinate
outside the wireless edge
31
Some of the forces driving WLAN (re)design
Migration to
IPv6
• The network hollows out
• The edge is used for sensing and reporting
• Policy definitions allow the network to dynamically reconfigure in response to
traffic & external events
• SDN APIs allow the network to dynamically reconfigure in response to external
requirements
Consumer devices in
the enterprise
Migration to
the cloud