Wireless ISP Infrastructure

1
Wireless ISP Infrastructure

• MikroTik
• Director - John Tully
• CTO Arnis Riekstins

2
AP Platform

• multiple radios per AP
• Increase aggregate bandwidth using
  non-overlapping frequencies
• Re-use of network configurations such as
  firewalls and users
• Network services closest to the user (PPPoE,
  DHCP, and PPTP)

3
From AP directly to client(no router on client
site)

• AP MAC registration table
• Assign IP to MAC with ARP disabled
• Restricted MAC level forwarding on wireless
  network

4
(cont) AP direct to client

• PPPoE access concentrator
• Overview
• AC configuration demonstration
• Window XP client configuration demonstration
• Encryption MPPE protocol, advantages in
  wireless
• Radius authentication
• no engineer needed for account changes
• automatic billing with legacy systems

5
(cont) AP direct to client

• Bandwidth setting
• Tx and rx settings allow you to simulate DSL
  offers
• Address assignment

6
(cont) AP direct to client

• PPTP
• DHCP assigns private IP address
• PPTP on Windows
• PPTP clients available back to Windows 3.11
• Radius authentication
• Scripting to set bandwidth (in v2.6)
• Demonstration of setup, server and client

7
From Wireless Client Router to Client LAN

• General description of client site router
• Protects wireless network from hacking by
  customers
• Offer services to customers
• Masqueraded address
• Static NAT for servers

8
From Wireless Client Router to Client LAN (cont)

• Multiple client connected to same router
• Per interface firewall
• Multiple ethernet interfaces in client site
  router
• Using a smart switch with router and VLAN tags on
  a port basis (v2.6)
• Using an ethernet bridge and PPPoE or PPTP

9
From Wireless Client Router to Client LAN (cont)

• MikroTik Packet Packer Protocol (M3P)
• Wireless has high per packet overhead
• Negotiating access to wireless medium
• Acknowledgment and error correction
• M3P packs small packets into a large wireless MAC
  packet and increase throughput up to four times
  (with 100 byte packets)
• Automatically discovers other MikroTik routers
  with this feature enabled

10
From Wireless Client Router to Client LAN (cont)

• Services to customers beyond an IP gateway
• DHCP
• Special firewall configurations
• Per IP address accounting (even on masqueraded
  addresses)
• Dedicated VPN tunnel between other offices
• LAN bridge between other offices

11
From AP to the backbone

• Backup Links / Failover
• OSPF
• Tunnels over non-OSPF networks to OSPF backbone
  networks
• Increasing throughput
• Aggregation of Interfaces multi-path routing
• PPTP tunnel compression

12
From AP to the backbone (cont)

• Types of backbone connections
• additional point to point wireless 2.4GHz
  interfaces using non-overlapping frequency or
  5.8GHz
• licensed frequency microwave systems
• DSL connection from Telco
• Lease line from Telco using v.35 HDLC or E1/T1
  interface in AP
• Use of HomePNA 14Mb/s interface up to 1.3km with
  one twisted pair
• Use of SDSL up to 2.3Mb/s and 5km (speed
  decreases with distance)

13
Bandwith shaping

• problems when there is no shaping
• users get high speed local services on a "luck"
  basis
• high paying users may get low quality service
  when bandwidth is not managed
• backbones to wireless may get overloaded
• basic description of queues and function
• where to put queues

14
Bandwith shaping (cont)

• simple queue and complex queue configuration
• boss at client site wants better quality for
  himself
• webserver and mail server may be specifically
  shaped based on usage
• varied IP subnets may be put into one group with
  a certain allocation

15
Bandwith shaping (cont)

• scripting may be used to change the bandwidth
  speed settings
• for a day speed and night speed
• tunnels linking enterprise networks may be shaped
  and charged according to speed
• for example, a VPN tunnel with ethernet bridging
  between a company warehouse LAN and main office
  LAN

16
Bandwith shaping (cont)

• DEMO CONFIGURATION AREA ON ROUTER FOR SHAPING

17
Interference and antenna co-location

• 2.4GHz frequencies (three non-overlapping)
• omni versus sectoral
• building top antenna co-location
• plan with barriers between antenna that have an
  overlapping frequency
• example, concrete structure such as elevator gear
  box houses
• mount on sides of building one floor or more
  below roof top so that there is concrete
  separating the antennas

18
Interference and antenna co-location (cont)

• 2.4GHz frequencies (three non-overlapping)
• omni versus sectoral
• Reflections (plus and minus)
• Signal may be reflected off another object to
  make a connection when there is no line of sight
• Reflections may cause a direct signal to be
  cancelled

19
Interference and antenna co-location (cont)

• Interference may be mistaken for cabling problems
• Cable is too long (10m or less is suggested for
  client site though locations close (less than
  2km) to the AP may have very long cable
• Water may have gotten into the strands of the
  cable (cable must be replaced)

20
Interference and antenna co-location (cont)

• Grounding may be incorrect (if you see small
  sparks when connecting cables)
• Radio cable may be located to some high voltage
  lines that can cause interference

21
Interference and antenna co-location (cont)

• change polarity of overlapping frequency antennas
  for a 20dB drop
• bandwidth test when installing antennas
• small movements of the mount location may make
  giant differences
• using antenna diversity
• radio power and amplifiers

22
Sample system design

• Situation proposed by audience