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2006.06.05 NANOG-NOTES IPv6 deployment at Comcast
- From: Matthew Petach
- Date: Tue Jun 06 06:19:43 2006
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Randy Bush, moderator of the next section
He begged to do the introduction for a
specific reason; deployment of IPv6
that is beneficial to this companies'
P&L; possibly the only one in existence
He did a very studied and purposeful view of
using IPv6 to benefit his company!
IPv6 @ comcast
Managing 100+ million IP Addresses
[slides are at:
Office of the CTO
Director IPv6 Architecture
Comcast needs for IPv6
Comcast plans for IPv6
simplistic view of comcast IP problem
20 million subscribers in video
2.5 set-top boxes per subscriber
2 IP per set top-box per DOCSIS std.
total 100 millions IP addresses needed
that's not including high speed data,
nor comcast digital voice, nor mergers/acquisition
Used to use RFC1918 for cable modems.
that space was exhausted in 2005
Comcast recently was allocated the largest part
of net 73 and has renumbered cable modems in that space.
In the control plane, all devices need to be remotely
managed, so NAT isn't going to help us
IPv6 is the clear solution for us
However, even we are starting now, the move to IPv6
isn't going to happen overnight.
Triple play effect on the use of IP addresses
2005 HSD only 2006 T+
Cable Modem 1 1
Home computer/router 1 1
eMTA (voice adapter) 0 1-2
Set top box (STB) 0 2
total num of IP addresss 1-2 8-9
(assume 2.5 STB per household
IP Addresses: Natural Growth vs New Services
nice graph--based on trends, not real data
use public address space
use "dark" space (pre-RFC1918 space)
federalization (split into separate domains)
(trying to avoid that)
deployment plans started back in 2005
deploy v6 initially on the control plane
for the management and operation of the edge devices
DOCSIS CM, set top boxes, packetCable MTA (voice)
be ready to offer customers new services that use
IPv6 LATER, not now--first step is to just be able
to manage their own gear.
migration to v6 must be minimally disruptive.
deploying v6 must be in roadmap for all vendors
ops, infrastructure, systems must be ready to support
over time, IPv6 will penetrate Comcast "DNA"
Deploy v6 for IP addrs of the CM and STB
architecture: dual-stack at the core, v6 only
at the edges
deployment approach: from the core to the edges
this is an incremental deloyment; existing
deployments will be untouched in the beginning
Follow same operational model as with IPv4;
lots of DHCP!
All routers on Comcast IP backbone are IPv6 eanbled
first ping on 10GE production backbone
TTLs aren't quite working properly, still
checking on that.
[so, even mainstream vendors still don't have v6
working quite properly yet]
New CM will be v6 ready (dual-stack capable)
On an IPv4 only CMTS, CM will have v4 address only
On v6 enabled CMTS, CM will only have v6 address
No CM boxes will have both; if they could support
v4 on all, wouldn't have this issue to start with!
Provisioning, Monitoring, Back-Office
mostly software upgrade problem
not unlike the Y2K issue
fields need to be bigger in database and web scripts
Should system "X" be upgraded for v6?
does it communicate with devices that are v6 only?
payload Q: does sstem "x" manipulate IP data that
could be v6 (store, input, display)
Comcast inventory analysis
About 100 systems
10 need major upgrades for transport
30 need minor upgrades just for display/storage
Back office management of cable modems.
network transport will still be v4
however, back office systems may need to be modified
to display/input/store v6 related data (CM v6 addr)
Payload can be v6 while transport is v4.
Basic IPv4 compliance taken for granted today
IP level component testing is limited
IPv6 is still new technology
maturity level of vendor implementations vary greatly
some have v6 for 10 years
even those have features not fully baked
others have nothing, will rush to buy 3rd party stack.
Bar for v6 product acceptance has to be higher than what
we typically accept now for IPv4
Formal v6 requirement list before purchasing
v6 conformance testing/certification to accept product
most engineers have heard about it, don't know much
can expect new hires to have 2-4 years of v4, but 0 v6
initial and continuous training process is critical!
CM (cable modems) (DOCSIS 3.0/2.0b)
Video/Voice back-end systems
Retail Market (Consumer electronics)
Video (eg TV with embedded cable modem)
Right now, provisioning system is most challenging.
some OSS vendors implement RFC2465 (deprecated)
some router vendor implement partial RFC4293 (new
combined v4+v6 MIB, but only v6 part)
comcast run OSPF v2 for IPv4
looking at OSPF v3 and IS-IS for IPv6
Integrating v4 and v6 security
Integrating v4 and v6 QoS
OSPF v2 and v3 share acronym, that's about it.
QoS code points will be challenging; mark, and
then trust QoS to deal with markings independent
of the type of packets the markings are on.
That's pretty much it. Not such a difficult
process, mainly making sure the vendors do the
right thing, beating on them with a big stick.
Q: Dave Huberman, ARIN--without going into
specifics of comcast--thank you, that's a
very big landmark! You have upgrade so many
items, spend all this time retraining staff,
training new staff; how do you sell this
gigantic cost to the 44th floor?
A: The cost is non-negligible, but it pertains
to business continuance, so in general executives
aren't going to say no to it.
Q: Lane?--similar question, it's an upper management
support question. It costs money to do this!
A: Extremely strong business motivation for doing
it in the case of comcast; a good object lesson
for others in how to get management on board
with v6 migrations.
More pushback from midlevel managers than from
the top levels has been seen, actually.
Q: Steve Schultz, NASA; any plans to implement
IPv6 multicast, interdomain? At some point,
will need to bring multicast to the set top
boxes? Will they need both v4 and v6 multicast
streams in core?
A: They only want one multicast stream, from
bandwidth size requirements, so will translate
at the edges for now from v4 to v6. This effort
is all for device management, though, so multicast
won't be an issue for a while.
Q: Doug Montgomery?; need for certification and
profiles--do you see LOGO program for v6,
A: Has been looking at v6 LOGO phase 1 and phase 2,
they go deeply into neighbor discovery, but
doesn't cover MIBs, or routing protocols, or
transports other than ethernet. It's a minimum
entrance requirement (phase 1 now, phase 2 in a
few months), but that's not sufficient on its
own; they have requirements above and beyond
LOGO phase 1 and phase 2.
Q: Merike, global security; some vendors have limitations
on their v6 security features; what has vendor response
been to them, since they're a big company.
A: They have had to raise pressure on a few, yes; but
since nobody wants to lose Comcast account, they have
Q: Tony Hain, Cisco. Doing this with management, not
seeing any demand from customers; customers shouldn't
know underlying protocols, so they'll never demand.
Is there a plan to eventually get it to customers?
A: it's really based on services they can offer;
if there's a service that's v6 only that they can
sell to customers, they'll roll out v6 to the home.
Q: someone from Juniper: why comcast needs 100 million
IP addresses. They use v4 right now, what do they
A: they don't have 100 million yet, that's what
they're growing to; using 10/8 and 73/8 for now,
may use some dark space during the migration
period. They're still using public space for
Q: Bora Akyul?, Broadcom; you mentioned this in the
certification. Plenty of RFCs that obsolete each
other. IPv6 is richly optioned protocol compared
to v4. How do you decide which options you want
to use? Will you publicize those to your vendors?
A: DHCP v6 vs stateless autoconfiguration, may be
conflicting methods. They decided they wanted to
use DHCP v6, NOT stateless autoconfiguration, for
Q: Exactly! will they use a lot of extension headers?
Q: No, keep it simple!
Q: Randy Bush, IIJ? Two things he knows;
a) what is the simplest way to get from here to there
b) don't try to convert the users--they don't need to
know what's happening at the protocol layer
Q: Matt, Yahoo, asks about whether they will be
planning to give net 73 back when the IPv6 conversion
A: Well, they have a bunch of other systems that
need to communicate using v4, until they have
a solution that can do v6, will keep the v4