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Implementing and Maintaining an ISP Backbone

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Title: Implementing and Maintaining an ISP Backbone


1
Implementing and Maintaining an ISP Backbone
  • Kevin Butler

2
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3
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4
Tier 1 ISP Backbones
  • Comprise some of the worlds largest IP networks
  • Tier 1 companies include Sprint, ATT, PSINet
  • UUNET has the worlds largest IP data network,
    presence on four continents and future expansion
    into Latin and South America

5
Service Level Agreements
  • SLAs are an important and prestigious tool in
    attracting and maintaining customers
  • Comprised of uptime guarantees and bounds on
    latency through various geographic regions
  • most ISPs currently have latency the US

6
Supporting the Customer
  • Quality and expertise of first-line customer
    support varies wildly between companies
  • depending on size, geographic location and
    company focus, some front-line support teams
    outsourced to third parties
  • some in-house high level support teams have
    skills equivalent or superior to NOCs

7
Network Operations Centres
  • Generally the teams concerned with backbone
    maintenance and support
  • trend towards consolidation into Super-NOCs
    (eg. one for Americas, one for Europe)
  • specialisation within NOC for product support
    (eg. dial, VPN, backbone NOCs)

8
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9
NOC Tools
  • NOCOL - Network Operations Centre On Line
    (freeware UNIX)
  • Mediahouse monitoring (mainly web)
  • Micromuse Netcool (now owned by Lucent) - used by
    MCI WorldCom, PSINet, BT

10
Dial Access
  • Dial is a major selling point, especially with
    customers who travel a lot or are their own ISPs
  • connections made through an Ascend MAX TNT, which
    can support up to 720 concurrent callers
  • back-end is a DS-3 into a backbone router,
    routers advertised by an IGP (eg. RIP)

11
Dial-Related Technologies
  • COBRA (Central Office Based Remote Access) allow
    building of virtual POPs by backhauling PRIs
  • RADIUS (Remote Authentication Dial In User
    Service)

12
Integrated Services Digital Network
  • ISDN customers authenticate by RADIUS similar to
    dial users
  • underlying architecture similar but dial
    equipment often administrated differently
  • ISDN maintained within same AS as backbone
    whereas dial often in its own AS

13
DS-1 and high-speed access
  • Customer connections usually multiplexed, come
    into DSU as a channelised DS-3
  • gateway routers on ISP side usually Cisco 7500
    series, increasingly using Cisco 12000
  • customers connect using Cisco 1604, 2621, some
    3600 series, very large customers use 7500 series
    routers

14
Gateway Routers
  • obtain routes from customers usually statically,
    but sometimes by BGP
  • usually run link-state IGP within AS (eg. OSPF,
    IS-IS)
  • Cisco 7513 backplanes 1.8 Gbps while 12008 does
    40 Gbps

15
Where does traffic go from here?
  • Most ISPs have two levels of networks above the
    access router
  • Metropolitan networks aggregate gateway traffic,
    generally city-wide (if multiple POPs in city)
  • transit networks aggregate metro networks
    traffic, responsible for inter-city transport

16
ATM Switches
  • Terminate long-haul OC-12, OC-48 circuits and
    metro rings
  • Choice of vendor contingent on ISP, commonly
    Newbridge, Fore Systems (ASX-1000 and ASX-4000)

17
Example of an ATM interface
TR1.EG1 interface ATM2/0 description To
HA13.BLAH1 3C1 atm vc-per-vp 512 atm pvc 16 0 16
ilmi ! interface ATM2/0.195 point-to-point descrip
tion To XR1.BLAH1 ATM6/0 ip address
146.188.200.98 255.255.255.252 ip router isis
Net-Backbone atm pvc 195 0 195 aal5snap clns
router isis Net-Backbone
18
Implementation of BGP
  • BGP run between autonomous systems and peers, as
    well as multi-homed customers
  • monolithic AS broken up into BGP confederations
    for ease of work
  • routes controlled using access lists and route
    maps

19
BGP
  • Communities are destinations that share common
    attributes (eg. through access-list filters)

BGP table version is 23718690, local router ID is
205.150.242.2 Status codes s suppressed, d
damped, h history, valid, best, i -
internal Origin codes i - IGP, e - EGP, ? -
incomplete Network Next Hop
Metric LocPrf Weight Path i24.64.0.0/19
198.133.49.7 100 0 6327
6172 i i24.64.0.0/14 198.133.49.7
100 0 6327 i i24.64.32.0/19
198.133.49.7 100 0 6327
6172 i i24.64.64.0/19 198.133.49.7
100 0 6327 6172 i i24.64.96.0/19
198.133.49.7 100 0 6327
6172 i i24.64.192.0/19 198.133.49.7
100 0 6327 6172 i i24.64.224.0/19
198.133.49.7 100 0 6327
6172 i i24.65.0.0/19 198.133.49.7
100 0 6327 6172 i i24.65.96.0/19
198.133.49.7 100 0 6327
6172 i i24.65.128.0/19 198.133.49.7
100 0 6327 6172 i
20
Advantages of BGP for User
  • Allows for load-sharing and redundancy
  • routes can be biased through AS path prepending
  • requirement is high-quality router with close to
    100 uptime to avoid connection flaps and
    subsequent route dampening

21
Common Customer Issues
  • Static routes on backbone - often difficult to
    spot, can cause very strange routing results
  • pull-up routes for netblocks smaller than /24,
    required to avoid BGP dampening
  • BGP recalculations - if done on a transit router,
    entire backbone segments can experience outages

22
Customer Requirements of the Backbone
  • Redundancy - networks are redundant but card
    failures can take down whole routers
  • physical connection to POP from customer is SPF
  • low latency - massive increases in demand on
    backbone makes this difficult
  • over 2 million a day spent on global backbone
    upgrades

23
DSL low cost, high speed
  • DSL might phase out ISDN connections
  • difficult to troubleshoot from network standpoint
  • connections pass through telcos frame or ATM
    cloud between DSLAM and VR
  • RedBack SMS (Subscriber Management System) 1000
    commonly used as VR

24
RedBack SMS 1000
  • Supports up to 4000 sessions
  • OC-3 out to metro network
  • traffic-shaping accomplished with profiles

atm profile samplecust counters shaping vbr-nrt
pcr 1000 cdvt 100 scr 100 bt 10
25
Increasing Capacity
  • Backbone capacity increasing at a huge rate
  • Traffic engineering combined with high backplane
    becoming increasingly important
  • many ISPs turning to Juniper routers
  • UUNET rolled out production OC-192c with Juniper
    M160 running MPLS

26
Juniper Routers
  • JUNOS supports MPLS and RSVP

isis interface all ospf area
0.0.0.0 interface so-0/0/0
metric 15 retransmit-interval 10
hello-interval 5
edit
27
Distributed DOS attacks
  • Can be very detrimental to backbone (even causing
    switch crashes)
  • Combated by rate-limiting ICMP on routers
  • Most effective defense is community-wide egress
    filtering requires co-operation throughout the
    Internet

28
Canadian Network Challenges
  • Geographically, population resides in virtually a
    straight line across the south
  • major focus is on southbound capacity to the US
  • CRTC regulations on telcos create different
    arrangements
  • heterogeneous network to the US, integration a
    big issue

29
Questions?
  • Anything I can clarify or expand on...
  • Thank you!
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