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Where are we going?

Where are we going?. Some of the forces driving WLAN (re)design. Consumer devices in the enterprise. Migration to the cloud. Migration to IPv6. Why do we need VLANs?. VLANs split up L2 subnets to control excessive broadcast & multicast traffic

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Where are we going?

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  1. Where are we going?

  2. Some of the forces driving WLAN (re)design Consumer devices in the enterprise Migration to the cloud Migration to IPv6

  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 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 RS Router Solicitation RA Router Advertisement SLAAC Stateless Address Auto-Configuration DAD Duplicate Address Detection ND, NS, NA Neighbor Discovery, Solicitation, Advertisement 2001:0db8:1010:61ab:0219:71ff:fe64:3f00 VLAN 1 Interface Identifier 64 bits Network Identifier 64 bits RA RS RS 1. RS to ff02::2 ICMPv6 type 133 (RS) RA 2. RA to ff02::1 ICMPv6 type 134 (RA) router lifetime 1800s preferred lifetime = 7d, valid lifetime = 30d RS Address MAC

  6. Moving WLANs to IPv6 – RAs meet wireless 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 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. VLAN 1 RA 1. RS to ff02::2 ICMPv6 type 133 (RS) RA 2. RA to ff02::1 ICMPv6 type 134 (RA) router lifetime 1800s preferred lifetime = 7d, valid lifetime = 30d Address list Address list MAC MAC

  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: Through VLAN pooling, by design From mobility events, where devices move from one AP to another Where VLANs are used to segregate, or manage traffic and clients are using different services

  8. Moving WLANs to IPv6 – multiple VLANs 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 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. VLAN 1 VLAN 2 RA RA RA RA 2. RA to ff02::1 ICMPv6 type 134 (RA) router lifetime 1800s, preferred lifetime = 7d, valid lifetime = 30d Address list Address list MAC MAC MAC MAC MAC MAC

  9. Moving WLANs to IPv6 – confused addressing The network learns VLAN assignments and check for incorrect source address as a security measure (e.g. anti-spoofing). VLAN 1 VLAN 2 RA RA 1. RS to ff02::2 ICMPv6 type 133 (RS) RA RA 2. RA to ff02::1 ICMPv6 type 134 (RA) router lifetime 1800s, preferred lifetime = 7d, valid lifetime = 30d 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. Address list Address list MAC MAC MAC MAC MAC MAC

  10. Moving to IPv6 – Solving mismatched IPv6 VLAN 1 VLAN 2 VLAN 3 VLAN 1 VLAN 2 RA RA RA RA 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 Address list Address list MAC MAC

  11. Moving to IPv6 – Unicast vs Multicast Multicast downlink frames beacon multicast TIM time client radio in receive mode Multicast to unicast downlink frames beacon unicast multicast TIM time data ack & sleep trigger 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 client transmits client radio in receive mode

  12. Moving to IPv6 – Solving mismatched IPv6 VLAN 1 VLAN 2 VLAN 3 VLAN 1 VLAN 2 RA RA RA RA What to do? Either… Prune RA traffic to only those devices that have outstanding RSs? Make sure we don’t mix VLANs on an AP? Try making Wi-Fi VLAN-compliant? Other ideas? 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 Address list Address list MAC MAC

  13. Some of the forces driving WLAN (re)design Migration to IPv6 Migration to the cloud Consumer devices in the enterprise

  14. Consumer devices in the enterprise Consumer devices on a home network Reference model is a small L2 network Not many devices, plentiful bandwidth Devices use multicast to discover each other, and services by Type and Name … through mDNS / DNS-SN / Bonjour

  15. mDNS and DNS-SD • mDNS Advertisement • serviceType (e.g.PTR) • domain • mDNS Response • serviceName (e.g. AlphaPrinter) • mDNS Response • serviceName (e.g. BetaPrinter) • mDNS Query • serviceType (e.g.PTR) • domain L2 network • mDNS Response • serviceName (e.g. GammaPrinter) App advertises service Some DNS-SD Service Types http://www.dns-sd.org/ServiceTypes.html http http ipp printer appletv Apple TV home-sharing iTunes Home Sharing App requests service RFC 6762 Multicast DNS RFC 6763 DNS-based service discovery DNS Domain Name Service Announcements ServiceType: Name Queries Responses Announcements ServiceType: Name ServiceType: Name ServiceType: Name 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 serviceTypequeries 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

  16. mDNS & DNS-SD VLAN 3 VLAN 2 VLAN 1 mDNS & DNS-SD Every service instance publishes/advertises when it comes up and responds to queries on multicast. Within a given service, all instances have visibility of all other instances… … except across VLAN or L2 boundaries Default is to flood packets

  17. mDNS-participating network architecture • 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 (ethersphere) #show airgroupstatus AirGroup Service Information ---------------------------- Service Status ------- ------ airplay Enabled airprint Enabled itunesDisabled allowall Disabled (ethersphere) #show airgroup blocked-queries AirGroup dropped Query IDs -------------------------- _touch-remote._tcp81834 _sleep-proxy._udp 2 _vnc._tcp 1819 _mediatest._udp91 _mediatest._tcp22 • 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 mDNS & DNS-SD with network participation ‘Network’ learns groupings by service and device When a service instance transmits (on multicast mDNS), the network swallows the transmission Network responds to mDNS DNS-SD Queries on behalf of service instances When other devices in the group are in different VLANs, packets are forwarded across VLAN boundaries Default may be to block mDNS per-service

  18. Consumer devices in the enterprise mDNS & DNS-SD with network participation, network must be capable of: Identifying whether a service type is allowed Identifying the ‘group’ which should have visibility of each service instance

  19. Subnets, VLANs and multicast control Multicast control: similar to VLANs but works across subnets VLANs: network controls what a port can see Subnets: L2 domains require a router to connect, breaks multicast

  20. ‘Proxy’ multicast architecture is not new ARP RFC 826 Multicast query Unicast response Over here, mate! Who has A.B.C.D? A.B.C.D 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 IPv6 Neighbor Discovery Proxy (e.g. NDP, ND, DAD) Multicast filtering (802.11v FBMS e.g. VRRP) ARP proxy (802.11v, u e.g. ARP)

  21. mDNS-participating network architecture External Configuration for groupings, permissions Internal policy decisions Policy layer applies rules, e.g. “this device or service instance is part of group X including these other members” mDNS proxy Traffic forwarding layer Identifies, synthesizes and forwards specific packets mDNS & DNS-SD with network participation Network takes the role of service directory away from the distributed mDNS model Network can add and advertise its own services • mDNS Response • serviceName • (e.g. AlphaPrinter) • mDNS Query • serviceType • domain • mDNS Advertisement • serviceType • domain

  22. Some of the forces driving WLAN (re)design Consumer devices in the enterprise Migration to IPv6 Migration to the cloud

  23. 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 Monitoring and managing corporate activity from remote locations to cloud-resident applications ‘Conventional’ model brings traffic to the data center from campus APs And remote APs (VPN model over Internet) As corporate locations become more distributed, and apps & services become cloud-resident, network managers become blind to corporate traffic The only touch point for network managers will be an IT-supplied and managed AP

  24. Some of the forces driving WLAN (re)design Migration to the cloud Migration to IPv6 Consumer devices in the enterprise 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. Why do we need VLANs? IPv6 IPv4 VLAN 1 VLAN 2 VLAN 3 • 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 • 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 Increase the size, reduce the number of VLANs to solve IPv6 issues

  26. Software Defined Networking (SDN) * https://www.opennetworking.org/images/stories/downloads/white-papers/wp-sdn-newnorm.pdf 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. 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.

  27. Abstracting the network model Security / Remediation Server Voice / Video Server Required action (response) Connection setup alert Can’t do this one, try again New device alert Internal policy decisions Policy layer applies rules, e.g. “this device or service instance is part of group X including these other members” Adjust QoS per stream Move to another AP New ACL / firewall Traffic forwarding layer identifies, synthesizes and forwards specific packets Abstract the network model to a policy layer Policy layer interfaces to external APIs, OpenFlow External APIs export sensing information, accept reconfiguration

  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 L3 traffic & services radio L2 traffic & services 802.11 mgmt 802.11 connected device • Radio information • Signal level • SNR • Authentication • Status • Identity • Role • Blacklist • 802.11 management • Associated • Data rate • Frame error rate • MAC • Sleeping • L2 • ARP • VLAN • mDNS • IP • DHCP • IP address • Multicast • IGMP • MC Neighbors • Mobility awareness • Origin & location • Roaming history • AP load • Neighbor APs • L4-7 • Sessions & protocols • Destinations, ports • Rates • QoS

  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 Devices & services discovery Blacklist association Determine Reachability Apply or change QoS Synthesize responses Move to ‘best’ AP 802.11 connected (or unconnected) device • 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 • Mobility awareness • Origin & location • Roaming history • AP load • Neighbor APs • L4-7 • Sessions & protocols • Destinations, ports • Rates • QoS

  30. A better way to think about architecture SDN policy decision layer reconfigure network to allow for changes and coordinate outside the wireless edge Local policy decision layer Abstract the wireless network model and make decisions for authentication, service whitelisting, load balancing… Policy enforcement layer apply authentication rules, firewall rules, QoS policy, multicast service manipulation Sensing layer report radio state, 802.11 state, authentication, multicast services, traffic

  31. Some of the forces driving WLAN (re)design Migration to the cloud Migration to IPv6 Consumer devices in the enterprise 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

  32. Where we are going

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