帮忙看一下我的ASR9000升级到哪个版本合适？

winterwang2013

各位大侠帮帮忙。
我有一台ASR9000，现在想起MPLS服务，但目前的版本不支持MPLS，能不能升级到4.3.4（MD）或5.3.4. 我可以用我的CCO 账号下载这两个软件。
请看我附件中的截图，思科网站上的4.3.4 后面的MD 是什么意思？怎么是ASR 9001？

RP/0/RSP0/CPU0:ios#sh version
Tue Sep 17 01:37:36.024 UTC

Cisco IOS XR Software, Version 4.2.1[Default]
Copyright (c) 2012 by Cisco Systems, Inc.

ROM: System Bootstrap, Version 1.06(20120210:003513) [ASR9K ROMMON],

ios uptime is 3 weeks, 4 hours, 33 minutes
System image file is "bootflash:disk0/asr9k-os-mbi-4.2.1/0x100000/mbiasr9k-rp.vm"

cisco ASR9K Series (MPC8641D) processor with 4194304K bytes of memory.
MPC8641D processor at 1333MHz, Revision 2.2
ASR-9006 AC Chassis



2 Management Ethernet
8 TenGigE
8 DWDM controller(s)
8 WANPHY controller(s)
219k bytes of non-volatile configuration memory.
977M bytes of compact flash card.
67988M bytes of hard disk.
1605616k bytes of disk0: (Sector size 512 bytes).
1605616k bytes of disk1: (Sector size 512 bytes).


RP/0/RSP0/CPU0:ios#sh platform
Tue Sep 17 01:38:03.352 UTC
Node            Type                      State            Config State
-----------------------------------------------------------------------------
0/RSP0/CPU0     A9K-RSP-4G(Active)        IOS XR RUN       PWR,NSHUT,MON
0/0/CPU0        A9K-8T-L                  IOS XR RUN       PWR,NSHUT,MON
RP/0/RSP0/CPU0:ios#