-mccann dmm flatarch 00 - internet engineering task force · -mccann dmm flatarch 00.txt march 26,...
TRANSCRIPT
HUAWEI TECHNOLOGIES CO., LTD.
www.huawei.com
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draft-mccann-dmm-flatarch-00.txt
March 26, 2012
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Outline
Drawbacks of Existing Hierarchical Tunnel Solutions
Elements of a Flat Wireless Internet Service Provider
Mobility Management
Secure Binding of Assigned Address
Conclusions
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Existing Practice: Hierarchical Tunnels
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eNB
eNB eNB
eNB
Internet
S-GW S-GW
P-GW
S1
S5/S8
Gi
Inefficient
Routing
Single Point
of Failure
Encapsulation
Overhead
Wireless-specific
router with
capex & opex
Many UEs will be stationary;
Most will be clients not servers
and don’t need a fixed address
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Typical Wireline Internet Service Provider
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Internet
Access
Aggregation
Core
Multiple redundant points
of connectivity to the Internet
Network appears as one
or more Autonomous Systems (AS)
to the peers in the Internet; runs BGP
AS100
Technology-specific Network
Access Servers facing customer
lines
Redundant aggregation routers act as
IBGP route reflectors for the access layer IBGP Peering Relationships
Shortcut link used in IGP (e.g., OSPF,
EIGRP, IS-IS) but NOT an IBGP peering
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Possible Future Wireless ISP
Page 5
BS
Internet Home DNS
Server(s)
Local Caching
Resolver(s) and
in-addr.arpa Server(s)
Access
Aggregation
Core
• Flat network of Base Stations
• Redundant upstream ISPs
• Redundant mesh of IP connectivity
• Not a strict hierarchy
• No single point of failure
• Blue routers are COTS
• (vanilla wireline routers)
BS
BS
BS
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Mobility Management in a Flat Network
Each BS owns a pool of addresses
Mobile nodes attach/authenticate, get an address
Upon attachment/authentication to new BS, send iBGP routing
update with NLRI set to the already-assigned address
All iBGP routers will set the new BS as the next hop
Punches a hole in the routing tables
Update is limited in scope if movement is within the same route reflector
cluster
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IBGP Routing Update
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1. UPDATE sent to parent
aggregation routers
3. UPDATE sent to core
routers 4. Core routers make BGP
policy decision and route
traffic on direct path to new
base station
2. UPDATE reflected
down to all access routers
in the same cluster
5. Traffic from old base
station may follow direct
routing path if available
BS
BS
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IBGP from an HA
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BS
Internet Home DNS
Server(s)
Local Caching
Resolver(s) and
in-addr.arpa Server(s)
Access
Aggregation
Core
BS
BS
BS
Home Agent
MN that moved
out of local AS
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BS BS
Alternative Solution: Dynamic HA in the AR
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Original Point of
Attachment
(IP assigned from
this local pool)
Current Point of
Attachment
1
2 3
Traffic Traverses
Backhaul 3 Times • Assign original BS as a dynamic HA
• Send a Registration Request or Binding
Update from the new point of attachment
• Inefficient if backhaul is expensive and
scarce
• Requires MN to send IP packets
at new BS
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Issues
How does new BS learn about the already-assigned address?
How does new BS guarantee the assignment is authentic?
Answer: DNS
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UE BS H-DNS L-DNS
Authentication
BS learns MN’s DNS
name & agrees on MSK
DHCP Address Assignment
Dynamic DNS Update
my-ue.example.com
192.0.2.3
Dynamic DNS Update
Mapping:
my-ue.example.com 192.0.2.3
A Target eNB checks this to discover IP address
Mapping:
3.2.0.192.in-addr.arpa my-ue.example.com
A Target eNB checks this to verify IP address
DNS storage of assigned address(es)
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UE eNB/
L-GW
H-DNS L-DNS
Authentication
BS learns MN’s DNS
name & agrees on MSK DNS Lookup of my-ue.example.com
my-ue.example.com
DNS Lookup of 3.2.0.192.in-addr.arpa
Mapping:
my-ue.example.com 192.0.2.3
Mapping:
3.2.0.192.in-addr.arpa my-ue.example.com
DNS retrieval of assigned address(es) during handoff
iBGP Routing Update
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Authentication without RADIUS/Diameter
Round-trips to the home network add to latency of handover
Leverage DANE work putting public keys into DNS
Public keys can be cached
Re-run public key based authentication on every new attachment
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Dynamic Re-Binding
During quiet periods, MN should re-run DHCP to get a new
address that is local to the current BS
MN must keep track of which connections are using which
addresses
Keep renewing the lease of used addresses (unicast DHCPREQUEST)
Remotely from current BS: the BS must add the Agent Remote ID
Garbage collect unused addresses & remove from Home DNS entry
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Data Point: BGP Pass-through Time
How fast does a BGP Update propagate through the network?
See “Measuring BGP Pass-Through Times” by Feldman, Kong,
Maennel, and Tudor
http://www.net.t-labs.tu-berlin.de/papers/FKMT-MBPT-04.pdf
Time for a BGP Update to be processed and resulting Updates to
be propagated (MRAI disabled):
Best case: 2.4 ms
Worst case: 400 ms
Variation due to 200ms polling interval in a particular BGP
implementation
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Conclusions
Existing tunnel hierarchies are inefficient and unnecessary
BGP is used in typical wireline ISP environments
BGP Updates can be used to handle mobility events
Must limit the time and scope of mobility for scalability
MNs can re-bind to new IP addresses during periods of inactivity
Performance studies needed
DNS names can be used as node identifiers
Leverage DNS as a mapping database to find current IP addresses
Leverage DANE for storage of public key material
Enhance authentication to remove AAA round-trips and eliminate
transport of symmetric secret key material
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